University of Ghana http://ugspace.ug.edu.gh LIFE-TABLE STUDIES IN CULEX SPECIES AND THE SUSCEPTIBILITY OF CULEX QUINQUEFASCIATUS SAY TO INSECTICIDES COMMONLY USED IN ACCRA, A THESIS PRESENTED TO THE DEPARTMENT OF ZOOLOGY OF THE UNIVERSITY OF GHANA, LEGONr FOR THE DEGREE OF MASTER OF SCIENCE By REUBEN ESENA MAY, 1 9 8 2 , University of Ghana http://ugspace.ug.edu.gh department of zoology UNIVERSITY OF GHANA, LEGGSJ GHANA This is to certify that this thesis has not been submitted for a degree to any other university. It is entirely my own work, and all help has been duly acknowledged. (REUBEN ESENA) University of Ghana http://ugspace.ug.edu.gh CONTENTS SECTION t>ag 1. INTRODUCTION .. .. • • 9 t • t 1 1.1 Description of study sites «■* Malam and Nima.* 11 1.2 Climate of Accra Area .• .. * - 19 1.3 Pesticides that have been used in Accra « • 20 2. MATERIALS AND METHODS . - 4 ♦ • «» 23 2.1 Life-Tables •• .. 9 • • * 23 2.2 Weekly samplings *. ,. • • 24 2.21 Light traps .• .. . . •• 26 2.22 Sticky traps ,, .̂ • • • • 29 2.3 Physico-chemical characteristics of soil and water 30 2.4 Insecticide susceptibility tests • • * • 33 3. R E S U L T S •• .. .. .. • • 36 3.1 Life-Tables ,. .. •. 36 3.2 Weekly samplings . . . . . ■ 54 3.21 Light traps . . „ . . . . • t « 62 3.22 Sticky traps . . , . . , • « 65 3.3 Physico-Chemical characteristics of soil and water 70 3.4 Insecticide susceptibility tests 9 9 75 4. GENERAL DISCUSSION AND CONCLUSION « • 98 5. SUMMARY . . .. .. • 9 119 6 . RECOMMENDATIONS , , ,. t ( 123 7. ACKNOWLEDGEMENTS . , ,, O 9 124 8 . REFERENCES . , , . .. t « 125 9. APPENDICES . , . , ,, * « 130 University of Ghana http://ugspace.ug.edu.gh 1 1 a IN T RQDUCTION Interest in Cutex qu£nque fa so i atus Say ( = f atigans Wied) has been increasing with the growth of urban areas in the tropical zones of the world because this rjmosquito is an important vector of bancroftian filariasis. When increased urbanization is accompanied: by inadequate sewage treatment, conditions are ideal for proliferation of Cm qu 'inquefa&ei a t u s m No other species of mosquito has benefitted rfiore from these acute sanitary problems than has C• qu£nquefaso'£atus» For its. egg deposition and larval development, this species finds optimum conditions in water with a high degree of organic pollution. Usually, mosquito larval and pupal surveys are made to provide guidance for control programmes. They can be designed for species, geographic and habitat distribution, parasitism and density. In Ghana, Macfie and Ingram (1916] working on the seasonal distribution of the adult and larvae of mosquitoes in the various districts of Accra and Chris ti an sborg concluded that Aedes aegif-pt'L and Cutex quinquefaso'Latus are two dominant species but that Am a&gypti- was more common. Earlier, Graham University of Ghana http://ugspace.ug.edu.gh 2 (1910) had studied the mosquito larvae found in water - receptacles at Lagos, Nigeria and found that a seasonal variation in numbers was shown to occur, but the causes were obscure. In this study, 2 active natural enemies: of mosquitoes were found to exist. One natural enemy of mosquito larvae was Cu lex ti'g ripes* The other was: a small active surface-feeding fish RapZochtZus- gvaham'Zm This fish has a great capacity for populating flooded land by leaping from one pool to another. Catfish, however, preys on these fish. In recent years, many basic studies on various aspects of Cm quznque fasci-atus population biology and disease rela­ tionships ti.e. filariasis) were initiated in Rangoon, Burma. The results of these studies were reported by de Meillon et. aZ- (.1 967). More recently, Chinery (.1 965 , 1 968a, 1 968b) studied the mosquitoes in Accra with emphasis on their breed­ ing places, in relation to the mosquito control in an urban environment. He found that proliferation of Cm quCnquefas- czatus ( = fatigans) is due mainly to urbanization associated, with the use of insecticides in preference to conventional sanitary- measures. The most recent study on pre— adult population of Cm q u inqu&fa&ciatus in West Africa was conducted by Subra (.1 970), Patterson et. aZ-(1 970). They studied the University of Ghana http://ugspace.ug.edu.gh 3 seasonal variation of the population. Weidhass et a t• (1 97 1 , 1 973) also studied C. qutnq uefasstatus in an effort to suppress and eliminate the species using s; te ri le m a le s • Referring to the previous studies in Accra, one observes that life-table studies and other quantitative studies on the population dynamics are lacking. It is known that the quantitative ''determination of mosquito larval abundance is a primary requirement of both mosquito control and research programmes. Generally, studies on mosquito dynamics are deficient on two accounts (Anon, 1968)• 1. There are few ‘adequate studies' of total numbers of eggs, larvae, pupae and adults in any sample. 2. The many effects of the environment on survival and reproduction have not been fully explored, still less adequately quantified. One aim of entomologists is to develop technologies that will give the required degree of control most effecti­ vely, efficiently and economically. Such an aim implies that the control of diseases caused by mosquitoes should be based on the management of total populations rather than the continual reduction of high density populations at times when the insect or disease becomes a problem. In most cases, University of Ghana http://ugspace.ug.edu.gh 4- it is possible to visualize the way in which a control technique will act on an insect population. However, the development of the potential of new or integrated approaches to control is less available. As a contribution to planning integrated control measures, scientists have in recent times relied on life-table construction. The purpose of this is to summarize the survival and mortality rates of a population. Its applica­ tion in recent times is found in agricultural and forest entomology (Morris 1963 , Southwood 1966, Varley and Gradwell 1 9 7 0 ), and in fisheries biology (Ricker 1944, 1948, Wohlschlag; 1954, Beverton and Holt 1957). Only recently has it been applied to mosquitoes (Lakhani and Service 1974, Service 1 97 1 , 1 973, Southwood e t m a l , 1 972). Varley and Gradwell (1970) emphasized that the most instructive life-table will usually be based on the conti­ nuous and intensive study of a population in a single habitat, not by sampling different populations in a number of similar habitats: in different years. Where sampling is for life-table construction, diffe­ rences in sensitivity of larval instars to disturbance produce biased samples. The 'enclosure method* whereby a given area is enclosed and all the larvae contained in the University of Ghana http://ugspace.ug.edu.gh 5 area removed as practised by Cambournac (1939), Bates (1941] and Goodwin and Eyles (1 942) are more suited to the study of extensive areas of shallow water with much vegeta­ tion, where larvae are numerous and evenly distributed. Zn the types of breeding site indicated^ this method is difficult to perform, because the larvae accumulate along the 'shore line* and not in the open area of the water habitat. The method used by Christie (1954) for recovery and enumeration of An ophele s g ambiae from pools is however quite accurate and efficient and it shows that about 95% of the larvae of all stages except the first are recovered. In general, the specimen—collecting devices used in qualitative and quantitative studies are the same (reviewed by Bradley and Goodwin, in Boyd 1949) but, where in quali­ tative work the specimens collected are most frequently in themselves the end-goal, the number of organisms taken per unit of effort or area is important in quantitative studies. Additionally, quantitative surveys methods differ in that a sampling design and a mathematical model for data analysis must be developed. In some cases it is also required that a method be developed for determining the numerical rela­ tionship between the specimens collected and total population else. University of Ghana http://ugspace.ug.edu.gh 6 In connection with quantitative considerations, Andrewartha (1961a) recognizes two types of population densities. If it is possible to count or estimate all the animals in an area, the results are spoken of as the ab so lu te d e n s ity of a population. Where the'size of a population is known only as a ratio to the size of another population either in time or space, it is said that the r e la t iv e d e n s it y is, known. In order to understand the factors that determine mosquito numbers, knowledge of the effects of environment upon survival, fecundity and dispersal is necessary. The data required are the total numbers of eggs, larvae^ pupae and adults, in the area under study at different times, together with an analysis of environmental factors. Changes in numbers are then related to changes in environment. The analysis of such data is the subject of a paper by Hayes and Hsi (.1 975) , The sampling of larval density should aim at roughly estimating the relative density for quantitative evaluation* For this reason, the relative abundance of larvae of a particular species at different places can be determined, provided that the methods of sampling are standardized^ as far as possible. Prom experience by WHO, (Anon, 1975a) University of Ghana http://ugspace.ug.edu.gh the number of larval dips should be standardized as units of 10 dips or multiples of 10 dips (i,e, 2 0 , 30, etc*} per capture station depending on the density of larvae• The most recently designed larval trap (Service, 1981) is very efficient and may replace other aquatic light traps. Probably this is because the mosquito larvae and pupae easily get attracted to the two ends of a cylinder within which the uCyalume” chemical lightstick is suspended. It is therefore hoped that this light trap may be very useful for future work on Life-Table* Quantitative approach to Life-Table studies is very important in larval control. If the numbers of each stage (B«g« eggs laid, eggs hatching, larvae, pupae and emerging adults) in a population are counted, and the logarithm: of each number subtracted from that for the preceding stage, the results (the 'natalities* over the different age inter­ vals) are called K-values. The sum of the Revalues gives the total 'mortality' for the generation(Southwood% 1978), When a series of Life—Table are available for successive generations of a population, the quantitative relationships of such K-values to population fluctuations, to population density, and to various environmental factors may be determined. This involves the quantification of significant University of Ghana http://ugspace.ug.edu.gh 8 environmental factors as they change throughout the period of study. The objectives of such a Life-Table analysis make possible the recognition of (1) Environmental factors that are important for the prediction of population fluctuation and (2) the relationship of mortality (and dispersal) and each stage of the life cycle, and of natality, to population density. Knowledge of this relationship is essential for build­ ing a model of the way in which numbers are determined. Thus information derived from this type of analysis provides the ypb as is for the study of population dynamics. Studies of the effects of environmental factors on the mosquito throughout its life-cycle are also important. In this study, the sites at Malam (plate A) and Nima (plate B) were selected for the following reasons* Nima drain is one of the most polluted areas in Accra, with human and animal excreta, and the breeding site, apart from proximity to Legon is also permanent throughout the year. What is more, it is an area noted for the breeding of C u te x q u in q u e fa s o ia t u s (=f atigans) » The pond at Malam on the other hand, is an isolated area and inaccessible to the general public. The water is free from organic pollution, and also permanent throughout the year. Finally, the two University of Ghana http://ugspace.ug.edu.gh 9 sites were free from exposure to pesticides over the period of study. Also inhabitants of the 2 sites are of the same ethnic groups tHausas) • However, while Nima is drain is used for sewage disposal, there /improved sanita­ tion at Malam. Therefore, there is a vast contrast between the two sites. The first aim therefore is to compare the incidence of Cm q u in q u e f a s c i a t u s (=fatigans) in the two sites. Secondly, it is the aim of this study to find the other mosquito species occuring with C • q u i n q u e f a s e i a t u s in the two sites. The physico-chemical nature of the breeding sites was investigated with a view to determining the best time to control the vector- - thus reducing its mean density below the Economic Threshold. Since there has been little publication on insecticide susceptibility tests on mosquitoes of Accra, it was. also considered worthwhile to study the susceptibility of Cm q u in q u e fa s c ia t u s to some insecticides for comparison with levels obtained elsewhere. Even though this project of 12 months' duration is not long enough to confirm the seasonal fluctuation, it is however, hoped that it would serve as a guideline for future work. Furthermore, the work as a whole is extensive - University of Ghana http://ugspace.ug.edu.gh 10 covering many aspects — but the section of Life-Table studies, seasonal fluctuation and insecticide suscepti­ bility tests are topics of great interest and much quantitative work has been carried out. University of Ghana http://ugspace.ug.edu.gh 11 FrELD WORK 1.1 Description of Study Sites - Malam and Nima. Malam Locality! This; area is shown by the arrow on the map fig, 1. The pond in plate A is about 100 metres from the Accra-winneba road,and about;9 kin: from the sea, It is an open grassland and the dominant littoral vegetation is S e & u v i u m p o r t u l a e a s t r u m (Portulacaceae). Others are B o t h r £ o e h l o a b l a d h t i (Gramineae) and M a r i s o u s d u h % u s t C y p e r a - ceae). The study . site is a pond which has been artificially created as a result of an abandoned quarry by the Brick and Tile Division of GIHOC* It is an isolated place where there are 6 other such ponds, but only the selected one is infested by mosquitoes. This is probably due to the fact that the other ponds are infested by predators such as 0 gupppefejj ^ jie o il ia reti-oulata and tadpoles. There are other predators in the pond under study, however, but not guppies and tadpoles which are more efficient predators. Another reason may be due to the fact that the efficient predators being carried by floods from bigger ponds and a nearby lagoon during the rainy season are blocked by the heap of soil which separates the pond (plate A). On the other hand, the University of Ghana http://ugspace.ug.edu.gh 12 other ponds are often left exposed to the direction of the nearby lagoon. Even though, the pond is not very rectangular in shape, the length is 23,5 metres and the width is 7 metres. The surface area is 165m^ (approx.) There is a small pocket at one side. Strong wind normally blows from West to East along the direction of Winneba to Accra and the mosquito larvae are always concentrated at, one portion - where the samples are normally taken - as indicated on plate C* There is a random distribution of larvae when population increases and uniform distribution when the population decreases. A scum is sometimes formed on the water surface where sampling is normally taken. Current from the sea is obstruc­ ted by the heap of soil from the dug-out pond. The pond is an open place without tall trees, and there is no shade, no pollution and the water is permanent - V throughout the year. Nim a L o c a l i t y : This area is s h o w n b y the a r r o w on f i g . 1. The Nima drain as shown in plate B is a permanent drain which is one of the most polluted areas in Accra. All sorts of wastes such as sewage, human excreta, rubbish, empty tins University of Ghana http://ugspace.ug.edu.gh 13 and useless fiirtoiire and canyare /dumped into the exposed drain. The drain is a stream starting from the Airport Residential area and flowing to Asylum Down. The pollution starts from Accra Girls1 Secondary School. The drain is about 5 metres wide (about 7 metres at some parts), 0.5 metre deep and fast flowing. The dominant vegetation (littora1)along the drain ar^: 1 . A lt e v n t h e r a a e s s i l i s tAmarantheceae ) 2. S id a o v a ta (malvaceae) 3. Tpomoea o a a r i f o l i a (convolvulaceae) 4. Cucum eropsis e d u l i s * 5. E l e u & i n e i n d i c a (Gramineae) 6. Cynodon daixtylon CGramineae) There is a dense algal mat on the surface of the sheltered areas of the drain. Even though this is a fast flowing drain, it is slow at some parts - especially along the bank. Larvae normally concentrate along the algal mats on the surface in a com­ pound distribution because there are clumps of individuals, thus conforming to contagious distribution. The clumps themselves have random distribution. However, changes in density or life stages of the population causes changes in the distribution pattern - to random distribution. University of Ghana http://ugspace.ug.edu.gh r u K TTu N O F 1:250,000 SH EET L T 'A n ten frk ii\ V >A4y$» 1 A JL. -! jnyj Liap*V) 5*. VVi'fiok orM •• ' *.- Sri.i 'i puom" 1Vi“ Qs.imjsj odov^a^ (l Ufcuaf^y v r-,. CJituana .■\blU u3lrk"iff‘ kvtam NutoIjif1* T '•Uochi 'Ad. SasabK /* *. \O*c./ wtl*A jfcor*i % DjflnkronV* oll Wsawara ’tffbcro; \ Otinibi AValct 7 ■ .'■ , «/0r)ig«)yv M ■,—. — HMid-l< 'X00 mi pi v ivy#*4* jT, AV|»«m, (vtaai&umania VranV ̂cKiamiVi' .\yai>̂njary SJvkLvijU jnl»aSnQSr£yq~ ns,fO *\\ UfcA» ' -• ĵreJem » i; u/-t-i ̂ /-J+~>m̂ «j «. vV\ '.'■ Kwasunan ° tabadi M /)amSlaib4 on T_ I n » iristiansborg M a l a m A C C R A Ch o r k o r L a g o o n {[ |/T“ '■ \t) °f’* vt,̂‘4“Hn,#afr#iMAono N i m a ,#• ‘ •',>,V̂ ri7l^i*o'mefoln A k v ie t e m a n Legon ■'5Po x ; okrobite . 1 MAP OF ACCRA SH OWING STUDY SITES WITH £ RROWS. University of Ghana http://ugspace.ug.edu.gh 15 Plate A : Study Site at Malam ( A pond ) University of Ghana http://ugspace.ug.edu.gh 16 Plate B. Study Site at Nima ( A drain ) University of Ghana http://ugspace.ug.edu.gh 17 Plate C . Mosquito larval sampling with net at Malam. University of Ghana http://ugspace.ug.edu.gh 18 Plate D . Mosquito larval sampling with ladle at Nima. University of Ghana http://ugspace.ug.edu.gh 19 1#2 Climate of Accra Area The main rainy season is from April to July but there are some minor rains in March, October and November. During the 12 months under consideration, the total annual rainfall was 731.5 mm. The mean relative humidity at 0900hrs and 1500hrs was 81% and 69% respectively. Data for the past 10 years (1970-79) in Accra show, that the total annual rainfall was 795.2mm, The mean annual temperature was 27°C and the mean relative humidity at 0900hrs and 1500hrs was 81% and 69% respectively. Unfortunately, the climatological data of Weija the nearest station to Malam was not complete. However, for the periods of 1970-77, the mean monthly temperature was 25.9°C, and the mean monthly relative humidity was 84%. The mean relative humidity at 0900hrs and 1500 hrs was 84% and 72% respectively. The total annual rainfall was 886.4mm. University of Ghana http://ugspace.ug.edu.gh 20 1*3 PESTICIDES THAT HAVE BEEN USED IN ACCRA Kerosene is one of the earliest hydro-carbons used in urban areas such as Accra. Apart from kerosene, gas oil and petrol constantly drain from filling stations, and fitting workshops, .... into the gutters. Dieldrin was introduced in the early 1960s. Its chemi- cal name is 1,2,3,l4°>1O-hexachloro.6,7 epoxy 1,4y4a, 5,6 ,7,8 , ! ̂ 8a Octahydro exo 1,4, endo 5-8 dimethanonaphthaia^ (HEOD) . In the late 1960s Sheltox was introduced. Sheltox contains the powerful volatile shell insecticide - Vapona to kill flying insects rapidly, Vapona is used directly ..in ware- houses but is normally mixed with kerofosre n,deo.m/e sTthiec. cuhseem.i cal name for Vapona (Dichlor^N/d0s) is 2,2-dichloro vinyl o, o-dimethyl phosphate (DDVP). Other organochlorines used effectively are Endrinef ­and Aldrinp (soil insecticide) and Lindane (̂ -SHC). Aldrin (HHDN): 1,2,3,4,10, 10-hexachloro-l,4, 4a,5,8 , 8a-hexahydro - exo - 1,4- endo 5,8 - dimethanonaphthaluen^ Iie. It is used for foliage- spraying against insect pest 'on crops-. It is formulated as dust, emulsion or liquid. Again it is used as a wood preservative and a soil insecticide. Lindane (Gamma-BHC): gamma-1,2,3,4,5,6-hexachlorocyclohexane. DDT has also been widely used. DDT: Dichloro-diphenyl trichlo- roethane could be used as 5% DDT dust, as foliage insecticide. University of Ghana http://ugspace.ug.edu.gh 21 ~r The organophosphates used are G^onas Tetrachlorvin- phos 2-chloro - 1 - (2,4,5 - t ric hlor op h e n y l ) V in y l dimethyl phosphate. It is formulated as a dust, and wettable powder and used for: foliage spraying on crops. Also used as a space sprayir , against storage pest. It is used against flies in animal houses, and as a 3% dust for body application -against ectoH^s^sites poultry* Phosdrine has also been used against mealy bugs. Its chemical name is Menvinphos - Ci.s isomer of methy 3 - (Dimethyloxy^phosphinyloxy) crotonate, Ga^ona is used as 3% dust. The carbamates used is phostoxine: This is a mixture of Aluminium phosphide and Ammonium Car bon ate* It releases « phosphine (pH3) gas on contact with moisture. It is used and for disinfestation of stored products/ processed food* The use of all these chemicals contribute to the resistance of all vectors of medical importance that breed in gutters and stagnant water. The use of chemical pesticides is today, the indispen­ sable requirement for the control of various diseases* However, problems are encountered in their use, e,g* vector resistance, and ecological upsets* To advise on pesticide quality control in order to avoid these problems, the WHO Expert Committee on Vector Biology and control met in Geneva University of Ghana http://ugspace.ug.edu.gh 22 from 29th November to 5 December 1 977, (Anon, 1978) The Committee was asked to study pesticide specifications, and to provide guidance for improving the specifications of new types of formulations and active ingredients. The Committee recommended for the development of new insecticides with emphasis on field tests on efficacy and safety. It also recommended close collaboration with the Food and Agriculture Organization of the United Nations (FAO) in developing information Service in Pesticide standards, Temephos, particularly as 1% on Sand, is used extensively against Aedes a e g y p tt which breeds in containers of clean and potable water, XSi its 19th report (Anon 1 97 0) the WHO Expert Committee on Insecticides noted the development of synthetic py*e- throids, which were then looked upon as replacements for the natural product for use in aerosols for space treatment. Since that time, the situation has been completely changed fay the discovery of pyrethroids that are both highly insec­ ticidal and much more stable on exposure to light and air. They can be used for the control of agricultural and public health pests in situations where natural pyrethrum and earlier synthetic pyrethroids would never have been considered. University of Ghana http://ugspace.ug.edu.gh 23 2, MATERIALS AND METHODS 2*1 life t a b l e s Objectives; To regularly sample populations to try to construct Life-tables and to evaluate different sampling techniques such as light and sticky traps. (a. $ u/nMrtfatciiitiss) Lab or atory; Culex f a tig an from the field are made to breed in the laboratory. Females are g i ven anaefthetised rats for blood meal. Egg rafts laid by the female adults are counted into beakers containing water. The beakers are always kept in cages Farex and Cere lac are used as larval food. The water in the larval beakers'- is changed daily to avoid contamination. Daily counts of the dead larvae are made and recorded in a tabular form; and the dead ones eliminated from the beakers. Numbers of the various, stages are also recorded' ('Tables 10 and 1 1v 1 The experiments were repeated several times in replicates and the results recorded. Fie Id s Apart from weekly samplings for one year at Malam and Nima (Tables 19 & 20) daily samplings were made at Legon 'Table 4) * (Table 3)^Chorkor Lagoon/and also at Nima (Table 9) and Malam (Tables 6 and l\ to construct life-tables. University of Ghana http://ugspace.ug.edu.gh 24 2.2 Weekly Samplings Material and Method A pond net was constructed very simply using a ring of iron wire 38*5 cm. in diameter to which a bagWas attached. A round holewas cut in the bottom of the bag and a trans­ parent plastic cylinder (2.0 cm. diameter, 9 cm. long) was attached. A long iron handlewa? attached to the ring. During collection, the larvae are washed into the tube which can then be emptied directly into a bottle. When collecting larvae, the net is held at an angle and skimmed rapidly through the surface water near emerging or floating vegetation (Plate C). The use of nets permits the sampling of large areas of water in a relatively short time. The long handle facilitates collection from under high banks and other inaccessible situations, A total of 10 flips are made during each of the weekly sampling days of the week. Each sample is transferred into a separate bottle (containing 7 0% alcohol) to be counted later in the laboratory. Coun tincf sCounting of individual larvae was made and recorded by instar. With the increasing number of indivi­ duals, it became too difficult to count. The sample was mixed in 1OOmls of 70% alcohol to ensure a homogenous dis­ tribution. Ten mis of the sample in the solution was counted University of Ghana http://ugspace.ug.edu.gh 25 at a time. The correct number was then calculated after measuring the total volume in a measuring cylinder* Mosquito species recorded* Mosquito species recorded ares Culex deoens, C% duttoni3 C• quinquefas aiatus * Ct thalas;s'iu&s Aede& a'lhooeigha'luŝ Other aquatic life,- Aquatic animals, apart from mosquitoes, are: nymph, 2 Dragonfly adult (Libellulidae), 3 Notonecta, 4 Gerris, 5 Hydrometra, 6 Nepa (Nepidae), 7 Rhagovelia (Vellidae), 8 Coenagridae, 9 Cybister spp. larva, Cybister spp. adult? 10 Tadpoles. Material and methods A white plastic container of 9.2 cm. (diameter) to which a long wooden handle (like a ladle) is attached is used for collecting larvae from the drain. The 0.320 litre dipper is normally immersed in the breeding places at an angleof 45° (Place D). The surface water will flow into the cavity but care is taken not to fill this completely as otherwise some larvae will be washed out (if a dipper is immersed too slowly, the larvae are disturbed and go to the bottom with the result that many escape collection). There is an interval of 2 - 3 minutes between each dip to University of Ghana http://ugspace.ug.edu.gh 26 allow stage ill and IV larvae and pupae to return to the surface. 20 dips are normally made into separate bottles and later sent to the laboratory for counting. Dipper types and dipping techniques are reviewed by Bradley and Goodwin (in Boyd 1949) Mosquito species recorded Mosquito species recorded are: Culex decens, C. duttoni, C. thalassius, C. tigripes, C_. quinquefasciatus and Aedes aegypti. Other aquatic life The aquatic animals, apart from mosquitoes are 1, Tadpoles, 2. Guppies Paecilia reticulatus, 3, Syrphidae, 4, Tetanoceridae, 5. Chironomidae (Chironomus) and 6, Notonectidae (Notonecta). 2.21 Light traps: Aquatic light trap Inverted plastic cones are fitted to each end of a tube (inside which has been painted white with oil paint to reflect more light) "Velcro" is stuck and sewn round edge of plastic cone the apex of whictj hag an outlet (hole) for larvae to pass through. Again "Velcro" is stuck on inside of tubes, and cones can be fitted into tubes and easily removed. University of Ghana http://ugspace.ug.edu.gh 27 To ensure firm sticking, holes were drilled round the ends of the cylinder, and the velcro sewn to it with wire. Chemical lightstjck procedure; The lights tick "Cyalume" is bent to break the Anne? glass and the tube shaken. one end of the plastic tube is cut off and the contents poured into a suitable glass tube. The tube is suspended in the middle of the cylinder. Two Betalights are glued to each end of a plastic cylinder and suspended in the tube with the lightstick Pig. 2. The trap is submerged under water. Light Trap Under laboratory conditions, light trapped 95% of Cutex thalas&ius larvae and pupae. It is mostly effective against the larvae but pupae are also attracted to the light (Table 2 1) , In the laboratory, the sink was filled with water and large numbers of larvae and pupae introduced. The light trap was introduced and left over-night it attracted almost all the larvae, leaving a number of the pupae on the surface of the water. The light trap was used at Malam on the 28th May 1981 and about 18,500 larvae were trapped within a period of 12 hours (7 : p .m 7a .m. ) . The number trapped would however University of Ghana http://ugspace.ug.edu.gh 28 cn o o cco LlI co Xo Z) Q CL < cr i- I- < X -J o < I- o < < o or a. o LU < x Q I— CM O) Li_ Transparent Suspended cyalume Cylinder LAGOON. University of Ghana http://ugspace.ug.edu.gh 29 depend on the abundance of larvae in the pond* On the 19th Jun^19 a81bout 3,000 were caught in the same pond. At this time, the number of larvae had decreased in the pond. The light trap was also used at chorkor Lagoon from 6a.m.— 8p.m. on the 10th and 11th July 1981. The catches were, 1168 larvae and 208 pupae on the first day and 1,580 larvae and 45 3 pupae on the second day. Results obtained by comparing the effectiveness of the Light and Sticky traps on the field STe found in (Table 2 3). 2°22 Sticky Trap Lab oratory: The Rat and Mouse varnish was used in the laboratory. 5 large beakers (5 0Gmls) were filled with water. 50 larvae and 50 pupae were introduced into each. Into each beaker was introduced the varnish and a carpet of sticky layer formed on the water surface. Observations show that all the pupae were trapped almost immediately when they came to the surface. The larvae were not caught immediately bee ause larvae are active swimmers. The 1st and 2nd instar larvae which rely more on cuticular respiration were actively swimming in the water and did not come to the surface and therefore were not trapped immediately. Results are found in Table 22, University of Ghana http://ugspace.ug.edu.gh Field; The sticky trap ( V a r n is h ) was usad.in the field a t Chorkor* This was done by coating a plastic sheeting 30,0cm by 16*0cm with the varnish and made to float on the water surface. A carpet of " V a r n i s h Scum" was formed on the water surface, and all the pupae were trapped on the water surface. Some larvae were also trapped* but the sticky trap was found not e f f e c t i v e for eggs and 1st and 2nd instar larvae (which also rely on cuticular respiration). 2*3 Physico-Chemical Characteristics of Soil and Water- Determination of Salinity The aim of this study was to compare the salt content and site preferences of mosquitos: at the two areas — Malam and Nima, Salinity is expressed in terms of chloride (Cl~) Mate rials; - Graduated Cylinders of 10ml. - Weak Silver nitrate (analytical grade) solution 9,58g. per litre. - Strong silver nitrate (analytical grade) solution 47.9g. per litre. - Potassium chromate solution, 5%. - Brown bottles with droppers for silver nitrate solution, Procedure : Anonymous (1 975b) To 4 ml, of water from the breeding place in a gra­ duated tube, 3 drops of potassium chromateare added and mixed, University of Ghana http://ugspace.ug.edu.gh 3J The silver nitrate solution (weak or strong according to salinity) is added in the tube in small quantities and mixed well with the water after each addition. This is done by closing the opening with a rubber stopper and invert­ ing the tube 3-4 times. A red precipitate persisting after shaking indicates the end point of the reaction. The amount of reagent (silver nitrate) added is read on the graduations of the tube. PHYSICO-CHEMICAL CONDITIONS OF THE POND AND DRAIN The data Table 26 shows analysis of the water and soil s ample s . Methods used: pH of the water samples was taken electrometri- cally using a soil; water ratio of 1:2 and soil: 0,01 calcium chloride solution ratio of 1:2. Organic carbon was determined by the wet - combustion method of W alkeley-Black and Organic carbon converted to organic matter using a factor of 1.72. Sodium in the water sample was determined by the flame- photometer and in soil after extraction with neutral N NH^ 0 Ac solution. The dissolved O2 was determined by using the WINKLER METHOD, while chlorine was determined by WHO standard method ( A n o n y m o u s 1 975b). University of Ghana http://ugspace.ug.edu.gh DETERMINATION OF OXYGEN CONTENT THE WINKLER METHOD Material and Method: (1) From a 250cc. sample bottle con­ taining sample to be analysed, remove a stopper and by means of long narrow volumetric pipette, 1cc. of maganous sulphate solution (Winkler). 1) is added well below surface of water* In the same way, 1cc of KOH-KI solution (Winkler II) is added*. Precipitate forms immediately. (2) Stopper is replaced and sample mixed by inverting bottle several times. Precipitate is allowed to settle for a few minutes. (3) 1cc. of Cone H2SO4 is added to release the iodine. The bottle is. inverted several times for proper mixing. Sample is allowed to stand for 10 minutes. (4) 200cc. of sample is transferred to conical flask, a»dt titrated rapidly with N^40 sodium thiosulphate solution until iodine colour in the sample has been reduced to pale straw colour. At this stage, a few c.c. of starch solution is added and continued rapidly but continuously until blue colour first disappears (end of titration). University of Ghana http://ugspace.ug.edu.gh 33 2’ , if? im e c t Ic Ide SusceotjbjJJtv Teg Material and Method. (a) For a complete test with one insecticide, sufficient larval were collected from the field in order that about 300 individuals of the same species of Culex qutnqucfaseiatus Say (-fajfejgwfl Wied) were selected. They were in their 4th instar and Were retained in the water in which they were collected until selected for testing. Larvae showing abnormalities (for example a fuzzy appearance of parasites on the body surface), were discarded. Lots of 25 larvae were distributed in each of 12 small beakers, each containing 25mls. of water* Their transfer W35 effected by merits of an eye-dropper> During the process, they were rirised lightly in clean water. (b) Into each of 12, 500-ml beakers, 225ml of water were placed* The vessels were such that.the depth of water w&S about 4.5cm. Pure water, free from chlorine and organic contaminants- (from upstream of the breeding site) was used. The average temperature of the water (H20)f4ts approximately 27°C. (c) The test concentrations were prepared by pipetting 1 ml. of the appropriate standard insecticide solution (DDT, DIELDRIN and LINDANE respectively) under the surface Of the water in each of the glass vessels and stirring vigorously for 30 seconds with the pipette. In preparing the series was of■concentrations, the most dilute / prepared first* There were two replicates at each concentration and two control University of Ghana http://ugspace.ug.edu.gh replicates, (d) Within 15-30 minutes of the preparation of the test concentration, the mosquito larvae were added to them by tipping the contents of the small beakers into the vessels. (e) After a period of 24hours, mortality counts were made. In recording the percentage mortalities for each concentra­ tion, the moribund and dead larvae in both replicates were combined. Dea:d larvae are those that cannot be induced to move when probed with a needle in the siphon or the cervical region. Moribund larvae are those incapable of rising to the surface (within a reasonable period of time) or showing the characteristic diving reaction when the water is disturbed; (f) Larvae that have pupated during the test were discarded. If more than 10% of the control larvae pupated in the course of the experiment, the test was discarded. Tests with a control mortality of 20% or more were considered unsatis­ factory and therefore repeated. (g) Additional concentrations were prepared both above and below .004 ppm. Additional intermediate concentrations were prepared by diluting a portion of a standard solution with pure toluene (e.g. a concentration of 0.01 ppm. may be obtained by diluting the 0.02 ppm. standard with an equal quantity of toluene before taking the 1 ml. for addition to University of Ghana http://ugspace.ug.edu.gh 35 the water in the beakers) (h) 4 replicates were performed with the same population of mosquito larvae, and this was used for constructing a baseline- susceptibility. The results were recorded in Tables 28,29 and To check for resistance, a discriminating dosage at 1 ppm (Fig. 14) was made and their values recorded (Table 34,37,40), These values were checked in accordance with the WHO larval surveys (Anon 1975a) , and results recorded (Tables 35,38,41), The survivors were reared to adults in the Laboratory and their Larvae (f,F2n) tested again for susceptibility to DDT, Dieldrin and Lindane respectively (Tables 36,39,42)* Calculations for mortalities were made using ABBOTT*S FORMULA. (Tables 28 to 30 and Tables 34 to 42). The values from this experiment were compared with the results of the WHO Test for susceptible Culex fatigans Wied (̂ quinquefasciatus Say) larvae obtained from Fiji> (Burnett & Ash 1961) and the values recorded in Table 43. University of Ghana http://ugspace.ug.edu.gh 336 3. RESULTS., 3.1: L f fe Tab 1es The following Tables and graphs, are the results obtained from the experiments and field data collection. The data in Table 1 showi total instars from the various sites. Table 1; INSTAR NUMBERS, DURATION AND LOGARITHMS OF NUMBERS/DURATI ON OF IMMATURE STAGES OF MOSQUITOES _ AT v a r i o u s SITES.____________________________________ Locali t} Des crip ti oh I II III IV P (SITES) NIMA x Instar numbers 2 0082 15451 1 0894 680 10130 (TABLE f) r ' In star duration 3 2 3 2 3 Larval N os Cu lex Instar duration 6694 7725.5 3631.3 340 337 6 . 6 gutnque fas oi a- Log larval No. tus Irtstar duration 3.8257 3.0879 3.5600 2.5315 3 . 52 84 % Instar Nos. 33 552 23Q87 1 3 948 1 36 09 133489 CHORK OR Instar duration 2.5 2 2.5 2 2.5 LAGOON I ns tar Nos , (TAELE 4.] Instar duration 13420. 8 11543. 5 5 57 9.2 6804 53395 . 6 C. tha­ lassius Log Ins tar Nos . 3.1277 4.0622 3,7466 3.8328 4.7274 Instar Nos, 41 0 348 269 226 1 30 LEGON (TABLE 3J Instar duration 3 2 3 2 3 (Fig .10) Instar Nos. • Ca du t- Instar duration 13 6 . 6 6 1 74 09. 67 1 1 3 43* 33 toni„ Log Ins tar N os . Instar duration 2,13 5 8 2 a 2 4 0 5 1.9526 2.0531 1.6368 ins tar N os, 4 7 6 02 32364 2 477 0 1 5 98 5 2 013 MALAM (TABLE 6} instar duration 2.5 2 2,5 2 2 „ 5 Instar Nos. Cu tha­ Instar duration 19040. 6 16 4 32 9908 7992 .5 8 0 5 a 2 lassius Log Instar No. j Instar duration 4.2 7 97 4.2156 3.9959 3.9027 2.9059 University of Ghana http://ugspace.ug.edu.gh 37 Table 2 ; INSTAR NUMBERS, DURATION AND LOGARITHMS OF NUMBERS/ DURATION OF IMMATURE STAGES OF MOSQUITOES AT VARIOUS SITES* LOCALITY & SPECIES DESCRIPTION I II III IV P Instar Nos. 17069 12136 8017 4765 4961 NIMA. Instar dura. 3 2 3 2 3 I(TdaMysl E q) Instar Nos.2- Instar dura. 5689.67 6068 26^2.33 2382.5 1653.67 Culek au^nque- Log Instar Nos fasoiapue Instar dura. 3.7550 3.7830 3.4269 3.3770 3.2184 CHORKOR Instar Nos 4006 3391 3923 2538 1891 TiAGOON ] Instar dura. 2.5 2 2.5 2 2.5 (TABLE 4) Instar NosInstard dura. 1602.4 1695.5 1569.2 1269 756.4 g B& £ - 5) Log Instar Nos lassius Instar dura. 3.2048 3.229 3.1957 3.1035 2.878 Instar Nos. 8087 5733 4327 2740 1652 Chorkor Instar dura„ 2.5 2 2.5 2 2.5 Lagoon Instar Nos. (TABLE 4) Instar dura. 3234.8 2866.5 1730.8 1370 660.8 Fig. 9 Log Instar Nos, (days 7-11) Instar dura. 3.5098 3.457 3.2382 3.1367 2.820 C. thala- ssius CHORKOR Instar Nos. 7972 7740 2659 3714 461 17 LAGOON Instar dura. 2.5 2 2.5 2 2.5 (TABLE 4) Instar Nos. (days 15­ Instar dura. 3188.8 3870 1063.6 1857 18446.8 19) Log. Instar Nos C. tha- Instar dura. 3.5036 3.5877 3.0267 3.2688 4.2659 lassius MALAM Larval Nos. 36440 25096 18776 1 1878 1587 (TABLE 6) Instar dura. 2.5 2 2 „ 5 2 2.5 (Fig.8) Larval Nos. (day 5-15) Instar dura. 14576 12548 7510.4 5939 634.8 log. Larval No. C. thala- . Instar dura. 4.1636 4.0986 3.8757 3.774 2.8026ssius * For graphical analysis, emphasis was laid on specific collecting days because it shows gradual trend in population reduction. For example day 2-6 at Nima means, from the second to the sixth day. University of Ghana http://ugspace.ug.edu.gh 38 Table 3: No. of immature stages of Culex dutteni caught each day of 20 _______dips fran larval habitat (pot hole) at Legon June 1981._______ University of Ghana http://ugspace.ug.edu.gh 39 Table 4: Mb. of immature stages of Culex thalassiua caught each day’ * of 20 dips from larval habitat at Chorkor Lagoon. No. d£ larval instars (i-iv) Collecting days & pupae (P) caught. Totals I II III IV P 1 1820 1610 1039 302 55 4826 2 401 736 1275 874 251 3537 3 353 593 1073 680 201 2900 4 578 202 311 475 821 2387 5 854 250 225 207 563 2099 6 1647 913 768 287 39 3654 7 2997 2200 1429 473 8 7107 8 2217 1583 1306 718 2 5824 9 1262 815 579 403 299 3358 10 421 382 443 880 1109 3235 11 1190 753 570 266 234 3013 12 2724 1564 1174 796 569 6827 13 4751 1995 834 2053 4595 14228 14 4365 1751 263 1481 4084 11944 15 3168 5062 606 1259 21426 31521 16 2031 1352 1007 673 13434 18497 17 1745 752 644 1424 3633 8198 18 525 216 136 192 5879 6948 19 503 358 266 166 1745 3038 33552 23087 13948 13609 58947 133489 * For graphical analysis, emphasis was laid on specific collecting days because it shows gradual trend in population reduction. For example day 1-5 means from the first to the 5th day. University of Ghana http://ugspace.ug.edu.gh 40 Table 5; No. of immature stages of Culex thalassius caught each week of 10 dips fran larval habitat at Malam. Collecting No. of larval instars (i-iv) Totals L>cv̂ S I II III IV P 1 1285 909 763 586 62 3,605 8 5535 4062 2943 1747 177 14,287 15 476 308 225 128 107 1137 22 4620 3502 2266 1608 1810 11,996 29 687 598 415 274 4 1,974 Totals 12603 9379 6612 4343 2160 32,999 University of Ghana http://ugspace.ug.edu.gh 41 : No. of immature stages of Culex thalassius caught, each daŷ of 10 dips from larval habitat at Malam, (20-5-81) - (23-6-81). For graphical analysis emphasis was placed on days 5—15 ̂ because of uniform population reduction during this period. No. of larval instars (i-iv) and Totals pupae (P) caucjht I II III IV ” P 1 1285 909 763 586 62 3605 2 2240 1556 1186 798 74 5854 3 3126 2171 1656 1115 138 8206 4 4511 3132 2389 1608 152 11792 5 6636 4608 3514 2367 321 17446 6 6201 4307 3284 2212 78 16082 7 5841 4083 3093 2057 152 15226 8 5535 4062 2943 1747 117 14464 9 4395 2845 2078 1182 395 10895 10 2923 1892 1381 787' 86 7069 11 1871 1210 892 497 78 4548 12 1048 728 556 372 46 2750 13 927 645 491 329 88 2480 14 587 408 319 200 59 1573 15 476 308 225 128 107 1244 47602 32864 24770 15985 2013 123234 University of Ghana http://ugspace.ug.edu.gh 42 Table 7: No, of immature stages of CuZex thatccssius caught each day of 10 dips from larval habitat at Malam, (3-6-81-22-6-81) Emphasis on day 5-18. Collecting No. of larval instars (i-iv) days and pupae (P) caught. Totals I II III IV P 1 476 308 225 128 107 1244 2 1280 906 760 646 61 3653 3 2306 1705 1232 741 74 6058 4 3439 2375 1745 1260 629 9448 5 6170 4285 3267 2203 656 16581 6 5368 3796 3189 2711 482 15546 7 5295 3893 2819 1687 239 13933 8 4620 3502 2266 1608 1810 13806 9 4294 2779 2021 1163 422 10679 10 3212 2230 1701 1145 102 8390 11 2428 1685 1285 867 205 6470 12 1596 1129 948 807 121 4601 13 1163 886 661 506 54 3370 14 831 609 441 261 26 2168 15 687 598 415 274 4 1978 16 531 385 263 151 48 1378 17 536 246 187 125 15 929 18 230 159 121 84 8 602 19 366 235 179 116 36 932 20 519 345 264 157' 21 1306 45167 32056 23989 16640 5220 122972 University of Ghana http://ugspace.ug.edu.gh 43 Table 8: Total Yearly instars, instar durations and logarithms of respective immature stages:, of Culex quinquefasciatus at Nima and MalamfaTables IS & 20). Locality I II III IV P Larval numbers 6964 7653 4980 2677 2290 Instar duration 3 2 3 2 3 NIMA Larval Numbers Instar duration 2321.3 3826.5 1660 1338.5 763.3 Log.larval no/ Instar duration 3.37 3.58 3.22 3.12 2.88 Larval numbers 12603 9382 6612 4345 2160 Instar duration 2.5 2 2.5 2 2.5 Larval numbers MALAM Instar duration 5041.2 4691 2644.8 2172.5 864 Log larval numbers/ Instar duration 3.70 3,67 3.42 3.34 2.93 University of Ghana http://ugspace.ug.edu.gh 44 Table 9: No. of immature stages of Culex quinquefasciatus caught each day of 10 dips per bottle of 20, from larval habitat at Nima. Collecting No. of larval instars days pupae (P) caught. Totals I II m IV P 1 1443 2777 2128 1611 5016 12975 2 5538 3445 2202 1726 2127 15138 3 5959 4247' 2892 1281 589 14968 4 3269 2465 1701 492 131 8058 5 1016 537 683 1070 1312 4618 6 1287 721 539 196 802 3545 7 1570 1259 749 425 153 4156 Totals 20082 15451 10894 680 10130 63458 ------------------------- -Hi University of Ghana http://ugspace.ug.edu.gh 45 Table 10: Life-table of immature stages of Culex quinquefasciatus showing numbers and their conversion to base 1000. Expt. NE NP1 NP NA Adult No. N1 N2 N3 N4 surviving 1 200 150 126 96 64 52 48 18 6 1000 750 630 480 320 260 240 90 30 2 204 166 130 90 52 44 34 10 4 1000 814 637 441 255 216 167 49 20 3 206 178 128 82 76 58 46 24 14 1000 864 621 398 369 282 223 117 67 4 200 172 126 86 68 50 38 26 10 1000 860 630 430 340 250 190 130 50 5 200 168 130 80 64 42 30 26 18 1000 840 650 400 320 210 150 130 90 6 202 170 126 76 62 54 42 30 16 1000 842 623 376 307' 267 208 149 79 7 188 139 118 98 53 47 38 23 7 1000 739 628 521 282 250 202 122 37 8 200 151 120 96 64 52 24 19 8 1000 755 600 480 320 260 120 95 40 9 200 148 125 103 61 50 41 25 6 1000 740 625 515 305 250 205 125 30 10 197' 143 125 107' 58 43 36 16 6 1000 726 634 543 294 218 183 81 30 Total 10000 7930 6278 4584 3112 2463 1888 1088 473 Av. 1000 793 628 458 311 246 189 109 47 KEY: NE = Number of Eggs. N-, = Number of 1st instar larvae. n! . M „ 2 ^ „ „ . H i 3^ m H § * » « 4-(-h 11 M N* = No. of pre-pupae NP = " " pupae NA = " 11 of Adults, University of Ghana http://ugspace.ug.edu.gh 40 Table: 11 Life-Table for irrmature stages of Culex quinquefasciatus mean length of life is 4.84 days. LINE NE Ni N2 N3 N4 Npl N p A 1 . Population 1000 793 628 458 311 246 189 109 2. No. dying at intervals 207 165 170 147 63 57 80 3. % Mortality factors of 20.7 16.5 17.0 14.7 6.3 5.7 8.0 original 4. Successive % mortality 20.7 20.8 27.1 32.1 20.3 23.2 42.3 5. Successive survival 79.3 79.2 72.9 67.9 79.7 76.8 57.7 6. Fraction survival .793 .792 .729 .679 .797 .768 .577 7. Log (Pop.) 3.00 2.90 2.66 2.49 2.39 2.28 2.04 8. K-Value 0.10 0 . 1 1 0.13 0.17 0.10 0 . 1 1 0.24 Total K-value (viz:£k-value)=0.96. University of Ghana http://ugspace.ug.edu.gh 47 Table 12 Values for survivorship curve of Culex quinquefasciatus aS found in Fig.4. Mean length of life 4.84 days. X lx d lOOqx ex “Tx Lx Age Age as % No. '.surviv­ No. dying Rate of Mean (day:3 deviation ing at start within per 1000 Expecta­ frcm mean of interval age inter­ tion at length of val further life life 0 -100% 1000 207 207 3.2095 3179.5 896.5 2 -58.7 793 165 208 2.8789 2283 710.5 5 3.3 628 200 271 2.5039 1572.5 543.0 7 44.6 458 147 321 2.2478 1029.5 384.5 10 106.6 311 63 203 1.0739 645 278.5 12 147.9 246 57' 232 1.4898 366.5 217.5 13 168.6 189 80 423 0.7883 149 149.0 15 209.9 109 - - - - - 1 University of Ghana http://ugspace.ug.edu.gh 48 Table 13: Developmental time (days), and temperatures for iirmature stages of Culex quinquefasciatus & C. thalassius. June 1981. Larval Water Expt. NE N 1 N develop­ Tanp.N1 N2 N3 N4 P P ment. Egg-to °C. mergence 1 2.5 3.0 2.5 3.5 2.0 1 . 0 2.0 16.5 26.5 2 2.2 3.2 2.2 3.0 2.0 1 . 0 1.5 15.1 27.0 3 1.4 2.5 2.0 3.2 2.0 1.5 2.0 14.5 27.0 4 2.0 3.0 2.0 2.5 2 . 1 0.9 2.5 15.0 27.0 £ 8 .1 11.7 8.7 1 2 .2 8 . 1 4.4 8.0 61.1 27.5 2.03 X 2.93 2.18 3.05 2.03 1 . 1 0 2.0 15.28 26.9 1 1 .0 2.0 2.0 3.0 2.0 0.8 1 . 8 1 2 .6 27.0 2 1 . 0 2.5 2 . 0 2.5 2.0 1 . 0 1.5 13.0 26.5 3 1.5 3.0 2.2 2.5 2.5 1 . 0 1.5 14.2 26.5 4 0.8 2.5 2.0 1 . 8 2.0 0.8 2.0 11.9 27.0 I 4.3 10.0 8.2 9.8 8.5 3.6 6.8 51.7 27.0 1.08 X 2.5 2.05 2.45 2.13 0.9 1.70 12.93 26.75 KEY: NE = Number of eggs. " " 1 st instar larvae i k : .>» n 23nrdd „" „" N3 = N4 = m it 4th " " NP 1 = No. of pre-pupae Np = " pupae NA = No. of Mults. 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UJ OO A Ui UJ o —* ro a J i —1 UJ U l UJ a . a u to UJ UJ 'O “ Ul to A VD —i Ul a> u i 'J a i o 01 u3 ro ro to 0> o Ul 171 ,N r ' *-* a W Uj W •— —* — U l-4 KJ KJ UJ a u U l UJ Q ID \o VD 10 ro c> to KJ «■ s j KJ Ln n —* CD a U l o Ul o UJ o a t (E Ul Ul UJ to o CD 1 □ U l a Ul U l ___Q----- T A B L E 2 3 : S AMP LE OF CULEX T H A L A S S 'C H E S ON L IG H T AND S ' L A R V A E ( 1 ) P U P A E (P J T i AND D I F F E R E N C E ( d ) B E T t T IM E ( D A Y ) ( 1 0 . 8 . 8 1 ) 1 TRAP | | 1 p C d | L i g h t 11 1 1 3 4 3 8 6 1 5 2 0 ( 7 5 ) ( 2 5 ) 5 6 0 3 t i c k y 2 2 5 7 3 5 9 6 0 L i g h t 1 ( 8 3 ) (1 7 ) 1 66 1 (6 7 ) (3 3) 1 1 2 7 b t i c k y 1 1 37 31 6 4 5 3 L i g h t ( % ) 76 9 1 0 8 1 1 8 5 6 L i g h t ( % ) 6 8 8 1 5 0 8 2 1 9 6 ( 3 1 ) ( 6 9 ) University of Ghana http://ugspace.ug.edu.gh 67 S H > m a n b» n T3 H ii II || CJ in f M f M \r< W Ir^ m > 0 X? M t+ r * H ' r t #** »-■ ^ f t >— H- r h“ r+ ►< 0' c a *> P . p iD » P- d0 lO # H- rfP U.3J #> H- lO - H 1 I r 1 r t V N 0 w U — n •— w n w n w CT n H ‘ n Qi < r t rt r t 7f in Cf w r tf t • J *< ? < O's s * ffi |-r NJ —> —* cn _ >» a a NJ — - j n NJ u Ui o 01 NJ - * CD • O l O CO 'xJ u i tD cn U l mM 00 o Ul -J O Ut u i a Q1 U3 NJ rs> v n 01 CD —1 NJ U l i j l w w “ * " o w " * CD 0 0 o — . Oi U l _ • ^ UJ -» o> Nj « - * 1 (Ti N j a cn o CO NJ UJ - • C O ' «* —* —* u O -* ^0 •J ^o o a u i Ol -O — u CD ^ i> Ul 01 UJ kO UJ Ul ■C- n c/s — — w w w 01 -> 5o » >►9 JzC . 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U l UJ ID U l —* —* o 01 CD CD OI TJ — » •* H 03 ID ■J Ul - i U l 03 CD - j C3 NJ 03 “J —• NJ w H (/) •—< Cifl £'tj z 03 □ 03 0" 03 x j U l u t^> H Tj o O3 M 03 03 —* _» «-■ O CD a —• —* 0 rt M o■>J —i ‘ m cn cn ID m Ul Oi 01 OD c r > TJOD Ul 1 5 * d» M s kO * NJ _ • H o z 3D UJ U3 O vD O a WM »r a rt- J cn UJ o (I Or t !—• —1 n uj Ln ^ u Ul -J H 0) r j —* ■J —* m ID CD UJ —■ a\ n NJ CO 03 o M i-» NJ -J UJ N) Ul CD a CD CD , W ~ A NJ **• w — 0 0 * . Uj u i •j - > NJ - > u Ul _ _ _ NJ CD CD CD NJ Ul L>1 UJ 03 Nj vd id UJ M *0 -J NJ Ol TJ .~7*. cn 01 £• Ul o i a vJ Ui CD Uj NJ 00 o —* O -J W w — 1 - w UJ a Ol UJ m — 01 iv ID o o —» o o Ul 03 ' -* ui n o 01 a cn Ul a in o *sl 00 cn 0D v j Ui X. a Uj OD a U3 ID - j o U l T IM E (1 S I T E d i f f e r e n c e between c a t c h e s . Ratio of L ar v a e : Pupae in l i ght trap = 7 0 : 2 2 Ratio of L a r v a e : Pupae in S t i c ky trap = 38^62 University of Ghana http://ugspace.ug.edu.gh 00 TABLE 24 SAMPLE OF CULEX THALASSIUS POPULATION: SIMULTANEOUS SETS OF PAIRED CATCHES ON LIGHT AND STICKY TRAPS FOR TEN CONTINUOUS DAYS I ND I C A ­ TING TOTAL CATCHES (C) AND DIFFERENCE (D) BETWEEN CATCHES OF T H E TWO TRAPS AT CHORKOR LAGOON 10th AUGUST 1981 THROUGH ! 9 t h A UG . I 9 8 l University of Ghana http://ugspace.ug.edu.gh u* r X c c o 3 1 a m aUl u 2 *> in * u N* p1 1/1 m» X • • • • •to _ 4 • L- o •• •• <10 Ul to o r ♦(■ N o 0 • • • • o o o o o o o o o o „ r* to ►- r* u Nl v i N w N O to -4 «D i >o l/l Ul O tm w m U| N W • • • CD m o I Ui O U l \ CO ''I Ul O o o o o o O -N J 9 o o Ul o O \D 4-0 o o *“ IA“ V >4 toui u» v r w0 “ UJ O' - O - <45 o - O O O O o o • • • • •t* Ui o o OO o o o o o O O0 o o o o (J) 00 >1 <4 Ul «o v\ U ■» 00 00 Ui Ul• % • • • o o o o o o KJ o o o o o U l- OUli QUl o B Of 'U o to Ul QQ - o »i > O ■tf'O □BVA O' O' o to Ul u H- -J N * Obfn o> •M •- •♦ o o o o o o o o o o o vflUl O O' U1M3 O Q UlO - CM N Qb O O *vlt> NJ>0 Ntri mO' *N“ VMI — *» Oo u n ui o o Ul *-- O O OO0 -4 O O O O ♦ _10 to o o •'O ■- 16 • • • *+ o o o o o o o o o o o o CD to w u »• ->J O o f v \|IU I h> N VO N r. • w Ul N »• i* • • • • • W M 0 ► it •— *n O f t o o o o o — U ►* UU4 o o o o o ow w *j “ v -4 ^ f O * Ul 1' o * r r. ♦ 'N o \ * •» ! • U \ / 0 *« • *» N O f. . 1 in IV f * lw - OD ->J *» ». 0 o O C 1 £| O i l . 1 0 <> & 0 » r u hi to • • • % « • • • 1 1 • « • • • • « u ® r- VO O J ♦ 'O • O 0 f fVi| i U1 f U l a » O O N c to to •» 3> - ur . 0 >> o c J. » UI u 1 f>»»0 C f |\J v j O O o o • • • • ¥ — o o i N C o o o o o o o o o ao o o o o CD cz (/) I r ru n*• fv‘ O (VJ * rv ^ * .7 Ul ; N«ru a i in » o *- C * J"-* o «fl ti ■ UJ * t r o o r » V ».•* *» * L * 0 * -»-J• t • • • • • • • ' * • * • » *4 ► r t ’ « i 0* O d U“•l «K>* *- in N in o * V Cl Xu in o o N * - — O' a i o o .*» . i d Q a « ru 0 M 0 0 •> c* iov» o»’ r.a, a- w < u r. -j *•■ zr ) i U U> N M it ► • o u u u* «£> •4( •<:0 e. «< U. «. i 0 ,1 l 4» . .fo m (' C l i lU M O a r*-(71 U>0> *- N u O N O U1 * * * Ul €••/» -fy |V l>* r- (A o CD CD CD CoD TABLE 25 CALCULATION OF MEAN POPULATION DENSITY AND VARIANCE OF C U L E X T H AL A S S I U S POPUL AT ION, BASED ON DIFFERENCES BETWEEN C A T C H E S ON LIGHT AND STICKY TRAPS FOR TEN CONTINUOUS DAYS AT C H O R K O R University of Ghana http://ugspace.ug.edu.gh 70 3°3 P h y si c o- ch e mi c al c h ar a ct er i st ic s of soil and water D et er mi na ti on of Salinity: Remarks* 1 ml. of the weak silver nitrate. Solution to reach the end point of 4 ml. of water tested i nd icates 2.5g. of chloride per litre. Results: (a) For strong A g N 0 3 (water from Malam) i ii iii iv v Final 8 . 0 7 . 8 7 . 9 8 . 0 8 . 2 Initial 4 „ 0 4 . 0 4 . 0 4 . 0 4 . 0 V o lume 4. 0 3 . 8 3.9 4 . 0 4 . 2 Average volume = 3.98mls. (b) For weak A g N 0 3 (Water from Nima) i ii iii iv V Final 5 . 1 5 . 1 5 . 0 5 . 1 5 . 1 Ini tia 1 4. 0 4 . 0 4 . 0 4 . 0 4 . 0 Volume 1 . 1 1 . 1 1 . 1 1 . 1 Average Volume = 1.10 mis. C a lc u la ti on of Chloride content* This is obtained by m u l t i p l y i n g by 0.5 or 2.5 fas the case may be) the numbe r of m i ll il it re s of Si lver n itrate r eq u i r e d to reach the end point with a 4 ml water sample. (a) For strong salt (water from Malam) o «—i University of Ghana http://ugspace.ug.edu.gh 71 Average volume of water used - 3.98 mis. Chloride content = 2.5 x 3.98 = 9.95g Cl /litre, (b) For Weak salt (water from Nima) Average volume of water used = 1.1 mis. Chloride content = 0.5 x 1.1 = 0.55gCl"/litre. For strong AgN03 (Dried soil froni Malam) i ii iii iv V Final 5 . 3 5 . 2 5 . 1 5 . 2 5 . 2 Initial 4 . 0 4.0 4 . 0 4 . 0 4 . 0 Volume 1 . 3 1 . 2 i a 1 . 2 1 . 2 Average vo luine = 1 . 2 0 m i s . For Weak AgN03 (Dried soil from Nima) i ii iii iv V Final 5 . 0 5 . 0 5 . 1 5 . 0 5 . 1 Initial 4. 0 4.0 4.0 4,0 4.0 Volume 1 . 0 1 . 0 1 . 1 1 . 0 1 . 1 Average volume = 1.04 mis. Calculation of Chloride content (a) For strong salt (soil from Malam] Average volume of water used = 1.20 mis. Chloride (Cl“) content = 1.20 x 2.5Q = 3.0g Cl~/1. University of Ghana http://ugspace.ug.edu.gh 72 Treatment of Results: Determination of Oxygen content. If 2 0 0 c c . of sample is titrated, the n umb er of cc of the sodium t.hiosulphate solution used is n u m e r i c a l l y equal to the di ss olved oxygen c ontent in parts per m i l l i o n and no ad ditional c a lc u la ti on is ne cessary. This value m ul t i p l i e d 0.698 y ields O 2 di ss ol v ed in c.c* per l i t r e . Re s u 11s : Titration of Water from Malam. i ii iii Final 10 . 0 1 0 . 5 1 0 . 5 Initial 0 . 0 0 . 5 0 . 5 Volume 10 . 0 10 ,0 10 . 0 Average = 1 0 . 0 mis. Titration of water fromr Nima i ii iii Final 1 . 0 2 . 0 3 . 5 Initial 0 . 0 1 . 0 2 . 5 Volume 1 . 0 1 . o 1 . 0 Average = 1.0 mis. 1. The concentration of Oxygen in Malam = 1 0 ppm. or 6.98 cc, per litre. 2. The concentration of Oxygen at Nima = 1 ppm or 0.698 cc. per litre. University of Ghana http://ugspace.ug.edu.gh 73 Table 26: Physico-chonical analysis of water and 'Soil at Nima and Malam compared. PHYSICO-CHEMICAL ANALYSIS m TER SOXL Malam Nima Malam Nima 5-2-81 pH 6.9 8.2 5.9(5.7) 8.0(7.2) Na(i) ppm 15,000 370.0 700 35 (ii) meq/1 652.10 16.08 - - (iii) meq/lOOgSoil - - 30.43 1.52 °2 PE111 10 1 - - Cl" g/1 9.95 0.55 3.0 0.52 %C - - 0.433 0.216 Organi* c matter ^ - - 0.745 0.372 18-5-81 pH 3.2 7.9 5.9 7.2 Na (i) ppn 21,500 250.0 3,100 10.5 (ii) meq/1 847.82 10.87 - - (iii) meq/lOOgSoil - - 134.74 0.457 02 ppn 9.50 0.8 - - Cl" g/1 9.88 0.55 2.88 0.52 %C - - 0.35 0.19 Organic matter * - - 0.6035 0.3276 20-6-81 pK 3.8 7.8 4.1 7.1 Na(i) ppn 24,000 350.0 3,300 10.25 (ii) meq/ 1 1043.48 14.78 - - (iii) meq/lOOgSoil - - 143.47 0.446 02 ppm 10.5 1 . 2 - - Cl" g/1 9.75 0.55 2.75 0.52 %C - - 0.480 0.160 Organic matter * - - 0.8275 0.2758 # Average Organic matter of soil was 0-7253 for Malam and 0-3251 for Nima University of Ghana http://ugspace.ug.edu.gh 74 Table 27: Physico-chemical analysis of the water and soil at Nima and Mai am compared. ANALYSIS ON WATER SAMPLES: 5-2-81. location pH Na °2 Cl ppn meq/ 1 ppn gm/1 Malam 6.9 15,000 652.10 10 9.95 Nima 8.4 370 16.08 1 0.55 ANALYSIS ON SOIL SAMPLE 5-2-81- Location P11 Na. in H20 in 0.01m Organic in eq Cl" 1 : 2 CaCl %C matter ppn per gm/ 1 1 : 2 lOOg Soil Malam 5.9 5.7 0.432 0.745 700 30.43 3.0 Nima 7.73 7.2 0.215 0.372 35 1.52 0.52 18-5-81 ANALYSIS ON WATER SAMPLE location pH Na 02 Cl’ ppn meq/ 1 ppn gm/1 Malam 3.2 21,500 847.82 9.5 9.88 Nima 7.9 250.0 1043.48 0.8 0.55 University of Ghana http://ugspace.ug.edu.gh fc*. Oo -t>' CCDD f-Di ccrr 'O-J ° ̂HH “♦ « ecr _ a ro ~n =3 ro ■o - ro o OJ -nQ. oI o ow X2 °1 . . 0D OI Q— 3 n f rn CO Oe Ol CD — * = o 03 OJ c: a)* ^ r* ̂ I co m 2 ^ ro ro 2 n 5 2 ~ Oi OJ 0D r —1 --1t QQ. CD -n! OJ 3JCJo __ ro ro O n ro 3 'si n r- o- CD oi OJ CD o i D ro a— m rno o rot 19 o m n -- H ro ro 03 H t> ro (T) O r3o] ro r\) ■a ? ° ro ~sl n m ro “>l -Ck OJ 0D a OJ o Q m ro O l ° ~ 2 OJ o ro GD 5 < ro ♦ w* ° 2 ro : OJ ro 0 ) 3 J 03 OJ a ro ro ro ro OJ o CD OJ ro ->i 0 Qf u O — CD ro & ro o o v^1 -1 n o OX* QD >1 2 03 ffl O a-ro* "i tn o CD (/) o CD QD CD a 3 3 X3Q QD ->1 ■< "iQ CD O 9 c r P0 ro ~n1 O I OJ “0 o Ol io0 O I 01 OJ — O’ 01 • Cn 22 01 0 0 0 5 : 9 0J 3.4.. Insecticide Susceptibility tests* Tests Tota Is Date of- t e s t 25 2 8 Temperature during test ( °C) 1 In sect ic i de Mort. concentrot ion ( ppm) T ot al Total Total Tota 1 Total ( % ) corr * 87 3 13 7 5 ■ ■ 37 5 ; 2 1 ■6 7 27 3 4 2 9 - 8 0 0 2 4 7 - 8 2 5 4 3 - 5 2 4 8 5 0 4 6 - 8 9 2 5 8- 3 58 3 57 5 7 5 4 - 2 0 ■5 0 70 8 6 5 - 2 6 9 - 6 72 7 2 2 2 8 7 - 5 2 3 2 3 91-7 2 0 8 2-6 9 5 - 7 4 8 6 9 0 2 5 2 4 2 4 9 5 - 8 25 2 5 1 0 0 2 4 9 5 - 6 2 5 100 9 6 9 7 -9 C o nt ro l University of Ghana http://ugspace.ug.edu.gh t>* oo t> CD ^ cr CD IT n H < o3 - f O U) 2. a o O -T! ̂o O - o o w3 x> 5^ S r o ro ro 2 ? ° § ro CP- CD Oi * CD OJ O X) n «"7 airo T=Jo . c - J o QS. ° - ro CD CD cn oa Qn - ta o3 oE Q= a3 ^+ I° O s s ? l - ro ro ro £ CP ro (D r o T>CD a fD ro ro O ol ro CD CD CD OD o ro Qn ca>r -» ro•n ~o CD n< *-* ro < o fV)Q. _ cd 3 a — — ro ro° * CPo— a*> ro r o CD CD a a i U1 cn * ~0i o ro O OD oc r oj OJ IV) OD OJ - f 9 - 1 8 Table 29 TEST FOR DIELDRIN INSECTICIDE RESI STANCE IN 4th INSTAR LARVAE OF C U L E X Q UI NQUEF A SCI AT US C O L L E C T E D AT N I M A . ‘ j T e s t s T o t a l s D a t e of t e s t 2 5 - 2 - 8 2 - 3 - 8 1 - 3 - 8 1 T e m p e r a t u r e d u r i n g t e s t ( ° C ) M o r t . I n s e c t i c i d e T o t a l T o t a l ( % ) T o t a l T o t a l T o t a l c o n c e n t r a t i o n ( p p m ) c o r r . * ■ 0 - 0 0 2 16 7 2 6 - 1 18 2 2 4 3 0 2 9 29 2 3 0 - 4 3 9 3 6 - 4 3 6 5 7 0 ■ 0 2 5 4 - 2 6 0 - 9 54 5 5 9 5 9 55 4 0 0 6 6 - 7 7 3 - 9 68 2 6 7 0 5 0 75 0 2 0 2 0 2 0 7 7 - 3 7 8 7 9 - 4 83 3 2 2 2 2 8 6 - 9 2 2 8 5 8 6 84 8 2 5 2 5 2 5 1 0 0 2 4 2 4 95 7 2 5 2 5 2 5 9 9 9 9 98 9 C ontrol m orfa lify% University of Ghana http://ugspace.ug.edu.gh * n > o t> S3 V=* r-e* Hoi HCD ^ cr o CD ro cr O % 3 a; O n -» •n o ■u-♦ re a> H < H S S 1 5 ojCO O * Oo o "H TD 3 3 O •Q c/j O H ■“C ‘ ‘ c e .o ’ 2 — cmo n ■ > >cr 1 o o 2 o ro A ~(*t c- •r o -* - 5 OD ft S o . CD cn a. 3 " 3 c > ID -o» o a o«♦ * ^— cn 03fr 1 m - t *< o £ -♦ o -1 cu (D (T> r ' cn o n CD ro OJ 00 (J\ tD • m OD ve■ n«> ̂ c OJ G) «(D O 00 IE a? o cn University of Ghana http://ugspace.ug.edu.gh iQ o m c -n H m o rKo H O— o m ^t/> oOz X ° -oO rn2 ” ^ — O 2 O University of Ghana http://ugspace.ug.edu.gh Fig. |2 EFFECT OF DI ELDRI N I NSECTI CI DE C O N C E N T R A T I O N ON M O R T A L I T Y OF C U L E X QUINu J E F A S C I A T U S L A R V A E . (2.4 hours e x p o s u r e ) University of Ghana http://ugspace.ug.edu.gh PERCENTAGE M O R T A L I T Y 6 6 University of Ghana http://ugspace.ug.edu.gh PROBIT University of Ghana http://ugspace.ug.edu.gh 82 Table 31: Fitting a Regression line and testing the goodness of Fit (Data on Susceptibility of mosquito larvae to DDT) Insecticide Insects Observed Expected Observed Contribution concentra­ dead/ mortality mortality minus 2 tion. tested rate % rate % expected toX ppm corrected (fran graph) rate 0.002 17/100 7.7 1 1 . 0 -3.3 .01110 0.004 28/100 16.6 16.5 -0 . 1 .0000072 0.020 47/100 39.9 39.9 0.9 .00034 0.100 66/100 61.1 64.5 3.4 .00500 0.500 85/100 82.1 85.0 2.9 .00659 1.000 93/100 91.1 90.5 0.6 .0004187 2.500 99/100 98.9 95.5 3.4 .0268993 .0503552 The formula for calculating X2 for the individual differences is as follows; mX, 2i(~f or eac,h d,.i ̂ffe rence)x = —(O-b(Ex- served-expected p-ec—te—d- -m-or t ̂al:ri-try- ,- m - orttt-a-l-it%) x (. i71— esr _%00-E- )^ x-pe cted, mortality %) X3 = 0.0503552 = 0.0504 The average mosquito * 100.̂ the product of 0.0504 and 100 is 5.@4 X2 = 11.070 5.04 <11.070 It may therefore be concluded that the. line is a good fit and that the data are not significantly heterogenuous* The LC50 = 0.040 ppm LC95 = 2.20 ppm. University of Ghana http://ugspace.ug.edu.gh 83 CONFIDENCE LIMITS OF THE LC50 The confidence limits between which the LC5Q may be expected to lie with a probability of 95% may be computed by the method of Litchfield and Wilcoxon (1949). Two qualities must be calculated: the slope function (denoted S) and a factor (denoted fLC5o) that is applied as a multiplier to the LC50 to give the upper confidence limit and as a divisor, to give the lower limit. The steps are as follows: (1) The expected LC]_g and the expected LC3 4 are read from the regression line. (2) The number of mosquitoes tested at concentrations whose expected effects are between 16% and 84% is ascertained from the table of test data. The number is donoted N. (3) The slope function (S) is then computed by the formula: S = LC84/LC50 + LC50/LC16 2 (4) The factor (fLCsg) is obtained from the formula fLCso = S2 *77 / N ~ gexponent (5) Then, the LC50 X fLCso = upper confidence limit, and the LC5o/fLC5o = lower confidence limit, at the 95% probability level. The calculation is obtained from the data of Table 28 and the regression line fig, II the LC16 is read as 0.0035 and the LC84 as 0,43. The number of mosquitoes tested between the two limits N, is 100 + 100 + 100 k 300. University of Ghana http://ugspace.ug.edu.gh 84 The slope function S * 11.089285 Confidence limit, upper = 0.040 x 1.469 = 0.0 5876 Confidence limit, lower = 0.040/1.469 = 0.0272294 Therefore, it may be concluded, with 95% probability, that the LC50 of 0.04 0 will lie between the limit 0,059 ppm and 0.027 ppm. CONFIDENCE LIMITS OF THE LC95 The slope function S “ 314.38343 Confidence limit, upper = 2.20 x 2.508 = 5.51760 Confidence limit, lower = 2.20/2.508 = 0.8771929 Therefore, it may be concluded, with 95% probability, that the LCg5 of 2.20 will lie between the limits 5.518ppm and 0.877 ppm Table 32: Fitting a Regression Line and Testing the Goodness of Fit (Data on Susceptibility of mosquito larvae on DIELDRIN) Insecticide Insects Observed Expected Observed Contribution Concentra­ dead/ mortali­ mortali­ minus 2 tion % tested ty rate ty rate expected t o X % (cor­ (frcm rected) graph) .002 29/100 21.9 21.9 0.9 .0004882 .004 35/100 28.7 28.5 0.2 .0000196 .020 52/100 47.5 51.0 -3.5 .0049019 .100 74/100 71.4 72.5 -1 . 1 .0006068 .500 81/100 80.8 84.0 -3.2 .007619 1.00 92/100 91.2 92.5 -1.3 .002436 2.50 99/100 98.9 96.0 2.9 .021901 .0379725 University of Ghana http://ugspace.ug.edu.gh 85 2.X2 = 037925 = 0 ,0 379 The average mosquito * 100 the product of 0.0 379 and 100 is 3C79 at 5% probability level and 5 d.f. x2 = 11.070 3.79 < 11.070 It may therefore be concluded that the line is a good fit and that the data are not significantly heterogenuous. The LC50 = o019 LC95 = 1 . 8 0 CONFIDENCE LIMITS OF THE LC50 The slope function(s) is computed by the formula: LC84/LC50 + LC50yLC^g S = ------------------------- = 16.94 2 The factor^FLC5 q) is obtained from the formula: FLC50 = s2 ,77/N = sexP°n e n t- The exponent of the slope function is: Exponent = 2.77/ 500 = 2.77/22.36 = 0.12388 FLC50 = SO.12388 = 1 6 .9 4 0 . 1 2 3 8 8 Confidence limit, upper = 0.019 x 1.922 = 0.0365 ppm Confidence limit, lower = 0.019/1.922 = 0.00988 ppm. Therefore, it may be concluded with 95% probability, that the LC^q of 0.019 will lie between the limits 0.0 36 ppm and 0.009 ppm CONFIDENCE LIMITS OF THE LC95 The slope function(s) is computed by the formula: LC84/LC95 + LC9 5/LC 16 S = ----------------- ---------------------- = 857.226 The exponent of the slope function is: Exponent =2.77/500 = 2.77/22.36 = 0.12388 FLC95 =g0.12388 = 857.226°•12388 University of Ghana http://ugspace.ug.edu.gh 86 Confidence limit, upper = 1.80 x 2.309 - 4.1562 Confidence limit, lower = 1.80/2.309 = 0.7795582 Therefore, it may be concluded, with 95% probability, that the LC95 of 1.80 will lie between the limits 4 .156 ppm and 0.779 ppm Table 33: Fitting a regression line and Testing the Goodness of Fit (Data on Susciptibility of mosquito larvae on LINDANE) Insecticide Insects Observed Expected Observed Contribution concentra­ dead/ mortali- mortali­ minus tion % tested ty rate ty rate, expected to % % (from graph) .002 30/100 23.0 18.0 5.0 .0169376 .004 38/100 31.8 24.5 7.3 .0288092 .020 55/100 50.6 46.5 4.1 .0067571 .100 72/100 68.1 70.0 -1.9 .001719 .500 87/100 84.7 87.0 -2.3 .0036767 .00 92/100 90.2 91.5 -1.3 .0021729 !.50 97/100 95.7 95.5 0.2 .000080 X2 = .0578796 The average mosquito = 100 the produce of 0.0578796 and 100 is 5.788 at 5% probability level and 5 d.f. X2 = 11.070 5.788<11.070 It may therefore be concluded that the line is a good fit and that the data are not significantly heterogenuous. The LC50 = °*025 ppm LC9 5 =* ,210 ppm. University of Ghana http://ugspace.ug.edu.gh 87 CONFIDENCE LIMITS OF THE LC5Q The slope function(S) is computed by the formula: LC8 4/LC50 + LC50/LCI6 s = ---------5-----------= 14*775757 Confidence limit, upper = 0.025 x 1.718 = 0.04295 Confidence limit, lower = 0.025/1.718 = 0.0145518 Therefore, it may be concluded, with 95% probability, that the LC50 of 0.025 will lie between the limits 0.043 ppm and 0.014 ppm. CONFIDENCE LIMITS OF THE LC9 5 The Slope function (S) is computed by the formula: LC84/LC95 + LCg5/LCi6 Confidence limit, upper = 2.10 x 2.445 = 5.1345 Confidence limit, lower = 2.10/2.445 = 0.8588957 Therefore, it may be concluded, with 95% probability, that LC9 5 of 2.10 will i.e. between the limits 5 .134ppm and 0.859 ppm. University of Ghana http://ugspace.ug.edu.gh 38 Table 34 Susceptibility of Culex quinquefasclatus to Dlscrir iriating Dosage of lppp DDT in the Laboratory. Average mortality (corrected) 81% EXPT. NC used No of 9r Mortality Corrected % Date dead Mortality 1. 25 20 80 80 2 25 21 84 83 3 25 23 92 91 5 /5 /81 4 25 22 88 87 CONTROL 50 2 4 0 1, 25 19 76 74 2 25 20 80 78 3 25 20 80 78 7/53^1 4 25 22 88 87 CONTROL 50 3 6 0 1 25 21 84 83 2 25 20 80 73 3 25 16 72 70 9/5 /81 4 25 22 88 87 CONTROL 50 2 4 0 1 25 22 86 87 2 25 23 92 91 3 25 20 80 78 11 /5 /81 4 25 18 72 70 CONTROL 50 3 6 0 University of Ghana http://ugspace.ug.edu.gh 89 Table 35 Check for Resistance on Culex quinquefasciatus Larval Susceptibility test with lppxn DDT in the Laboratory Average Mortality (Corrected) 76% Expti1. No Used No Dead % Mortality Corrected % Date1 Mortality 1. 25 21 84 83 2 25 18 72 70 3 25 18 72 ! 70 13/5/81 4 25 19 76 74 C O N T R O L 50 3 ! 6 0 1. 25 20 80 78 2 25 18 72 70 3 25 20 80 78 15/5/81 4 25 19 76 74 COIfTROL 50 4 8 0 1 T 25 22 88 87 2 25 20 80 79 3 25 19 76 74 17/5/81 4 25 18 72 70 C O N T R O L 50 3 6 0 1 25 23 92 91 2 25 19 76 1 74 3 25 18 72 70 19/5^81 4 25 18 72 70 C O N T R O L 50 3 6 0 University of Ghana http://ugspace.ug.edu.gh 90 Table 36 Susceptibility of *F2 Generation "of Culex quinquefasciatius to lppm DDT in the Laboratory Average Mortality ( corrected) 62% Expt. No. Used No Dead % Mortality Coreected % Date Mortality 1. 25 15 60 60 2. 25 17 68 68 3 25 17 68 68 25/6/81 4 25 16 64 64 CONT R O L 50 2 4 0 1. 25 14 56 53 2. 25 16 64 61 3. 25 16 64 61 25/6/81 4 25 15 60 57 C O N T R O L 50 3 6 0 1 25 17 68 68 2 25 16 64 64 3 25 15 60 60 25/6/81 4 25 15 60 60 CONTROL 50 2 4 0 1. 25 18 72 70 2. 25 16 64 62 3 25 15 60 57 25/6^81 4 25 16 64 61 C O N T R O L 50 3 6 0 * *F2 Generation7refers to larvae that were obtained from survivors of discriminating dosage (lppm) and bred to adult stage in the Laboratory University of Ghana http://ugspace.ug.edu.gh 91 Table 37 Susceptibility of Cules quinquefasciatus to Discriminating dosage of lppm DIELDRIN in the Laboratory Average Mortality (corrected) 83% Expt. 1 No of Mosquito No. Dead 1 % Mortality Corrected I Date Used % Mortality 1. 25 23 92 91 2 25 23 92 91 3 25 20 80 79 5/5/81 4 25 20 80 79 C O N T R O L 50 3 6 0 1. 25 24 96 96 2 25 23 92 91 3 25 20 80 78 j 7/5/81 4 j 25 22 88 87 C O N T R O L 50 4 8 0 1 25 21 84 82 2 25 20 80 79 3 25 21 84 82 9/5/81 4 25 22 88 87 C O N T R O L 50 3 6 0 1 25 20 80 79 2. 25 19 76 74 3 25 18 72 70 11/5/81 4 25 20 80 79 C O N T R O L 50 3 6 0 University of Ghana http://ugspace.ug.edu.gh 92 Table 38- Check for resistance on Culex quinquefasciatus Larval susceptibility with DIELDRIN at lppm in Laboratory Average mortality ( corrected) 76% Expt No Used No. Dead % Mortality Corrected % Date Mortality 1 25 17 68 68 2 25 18 72 72 3 25 19 76 76 13/5/81 4. 25 20 80 80 C ONT R O L 50 2 4 0 1 25 19 76 76 2 25 18 72 72 3 25 17 68 68 15/5/81 4 25 18 72 72 CONTROL 50 2 4 0 1 25 21 84 83 2 25 22 88 87 3. 25 20 80 79 17/5/81 4 25 19 76 74 CONTROL 50 3 6 0 *. 25 18 72 70 2. 25 20 80 79 3. 25 21 84 83 19/5/81 4 25 19 76 74 CONT R O L 50 3 6 0 University of Ghana http://ugspace.ug.edu.gh 93 Table 39 ̂ Susceptibility of ̂F2 Generation * ‘of Culex qtiinquefasciatus to DIELDRIN at lppm in the Laboratory Average mortality ( corrected ) 63% ftcpt- No. Used N o . Dead % Mortality Corrected % Date Mortality 1. 25 16 64 64 2 25 18 72 72 3. 25 17 68 68 25/6/81 4 25 17 68 68 C O N T R O L 50 2 4 0 1 25 15 60 57 2 25 15 60 57 3 25 14 56 53 25/6/81 4 25 17 68 66 C O N T R O L 50 3 6 0 i. 25 16 64 64 2 25 17 68 68 3 295 16 64 64 25/6/81 4 25 15 60 60 C O N T R O L 50 1 2 0 f 25 17 68 66 2 25 18 72 70 3 25 16 64 61 25/6/81 4 25 15 60 58 C O N T R O L 50 3 6 0 * ’’F2 Generation"refers to Larvae that were obtained from survivors of discriminating dosage (lppm) and bred to adult stage in the Laboratory University of Ghana http://ugspace.ug.edu.gh 94 Table 40 Susceptibility of Culex quinquefasciatus to Discriminating dosage of lppm LINDANE IN T H E L A B O R A T O R Y Average mortality ( corrected) 87% , Expt No Used No Dead % Mortality Corrected Date Mortality % 1 25 22 88 87 2 25 21 84 83 3 25 23 92 91 5/5381 4 25 21 84 83 C O N T R O L 50 3 6 0 1 25 23 92 92 2 25 24 96 96 3 25 22 88 88 7/5/81 4 25 21 84 84 C O N T R O L 50 2 4 0 i 25 22 88 87 2 25 21 84 94 3. 25 23 921 91 9/5^81 4 25 20 80 79 C O N T R O L 50 3 6 o 1 25 21 84 83 2. 25 23 92 91 3 25 19 76 74 11/5/81 4 25 CONT R O L 50 1‘ 21 84 83 3 6 0 University of Ghana http://ugspace.ug.edu.gh 95 Table 41 Check for resistance on Culex quinquefasciatus Larval Susceptibility with lppm LINDANE in the Laboratory Average mortality ( corrected ) 75% Expt. No. Used No. Dead % Mortality Corrected % Date Mortality 1 25 21 84 83 2. 25 18 72 71 3. 25 20 80 79 13/5/81 4 25 18 72 71 CONT R O L 50 2 4 0 1. 25 18 72 70 2 25 18 72 70 3 25 20 80 79 15/5/81 4 25 19 76 74 C O N T R O L 50 3 6 0 1. 25 18 72 72 2 25 21 84 84 3 25 19 76 76 17/5^81 4 25 20 80 80 CONT R O L 50 1 2 0 1 25 22 80 80 2. 25 21 76 I 76 3. 25 18 68 68 19/5/81 4 25 18 64 64 CONT R O L 50 2 4 0 University of Ghana http://ugspace.ug.edu.gh 96 Table 42 < Susceptibility of T 2 Generation "of Culex quinquefasciatus to lppm LINDANE in the Laboratory Average mortality ( corrected ) 67% Expt No Used No. Dead % Mortality Corrected % Date Mortality 1 25 17 68 68 2 25 18 72 72 3. 25 16 64 64 25/6/81 4 25 17 88 68 C O N T R O L 50 2 4 0 1 25 16 64 62 2 25 15 60 57 3 25 17 68 66 25/6/81 4 25 18 72 70 C O N T R O L 50 3 6 0 *. 25 18 72 70 2 25 17 68 65 3 25 15 60 57 25/6/81 4 25 16 64 61 C O N T R O L 50 4 8 0 1. 25 20 80 80 2. 25 19 76 76 3. 25 IB 68 68 25/6/81 4. 25 16 64 64 C O N T R O L 50 2 4 0 * -F2 Generation "refers to Larvae that were obtained from survivors of discriminating dosage ( lppm) and bred to adult stage in the Laboratory. University of Ghana http://ugspace.ug.edu.gh 97 Table 43: Comparison of resistant Culex quinquefasciatus Say larvae in Accra, [Ghana .by R. Esena) with results of WHO Tests for Susceptible larvae from Fiji, when tested with DDT, Disldrin and Lindane. WHO R . ESENA (Fiji) Accra, Ghana LC50 LC35 LCSG LC95 Insecticide (ppm] (ppm) (ppm) (ppm) DDT 0.012 0.04 0.036 2.20 DIELDRIN 0.004 0.019 0.01 1 .80 LINDANE 0.008 0.025 0.032 0.210 University of Ghana http://ugspace.ug.edu.gh 4. GENERAL DISCUSSION AND CONCLUSION. 98 DISCUSSION The distribution of larvae within the breeding site is not uniform for the larval always concentrate around the borders and around different floating objects or vegetation. Here the larvae are seeking some support to avoid movement during feeding or to avoid being dis­ placed:. by the movements of the superficial layer of the water if there is slight current. The miscroscopic flora and fauna upon which Ot-C the larvae feed more abundant around the vegetation. In a breeding place where the water moves continuously (such as Nima) the larvae concentrate in those places where they will find a still harbourage especially along the banks. In a large stagnant water collection, first stage larvae are concentrated in places where the eggs were laid, but 3rd and 4th stage larvae move several metres away from the place of hatching and concentrate in the most favourable spots, in the shade or in the light, or near vegetation according to the species1 habit. Natural or artificial agitation of the water favours such dis­ semination of larvae, winds moving the superficial layer of the water will force the larvae to concentrate in quiet corners of the breeding space. Rain might wash out some breeding places or cause flooding, resulting in the larvae being transferred long distances, varying from a few metres to kilometres. University of Ghana http://ugspace.ug.edu.gh 99 The egg may be transported by fast flowing waters and may be destroyed by throwing them on to dry ground where they are rapidly dried by the sun. When larvae are in an advanced stage of development, they are more resistant to dessication and can survive several days on mud in the shade (Anon, 1975b), This shows how an environmental condition may play an important role in determining the concentration of larvae and why they should there~ fore be carefully considered when estimating larval density. It is a well known fact that mosquito populations, both adult and immature stages, are not dispersed at random but occur in concentrations over a wide and variable area. Most insect populations, however, have what is termed a contagious or aggregated distribution, and individuals occur in definite clumps leading to a parchy type of pattern. As most environments are not completely uniform, it is not surprising that certain areas will be favoured more than others and thus contain more individuals than less favoured sites, A characteristic of contagious distribution is a large variability of counts in different samples. In contagious distributions the variance is always greater (many times) that the sample mean (S2 > x). The type of contagious distribution may change, for example first instar mosquito larvae may exhibit a more highly contagious distributions than the later instars and pupae. Quantitative sampling of larval density with the available devices is far from accurate for the following reasons: (1) Larvae are not distributed at random in breeding places, but are often crowded in concentrated sites. Therefore it is difficult University of Ghana http://ugspace.ug.edu.gh 100 to extrapolate the data on larvae in the site sampled to all the surface area of each type of the breeding place. (2) Breeding places vary in size and shape and their surface area fluctuates with seasonal environmental changes. Therefore it is difficult to fix a standard surface area for each type of breeding place. The amount of aquatic vegetation also varies, which increases the difficulty of reliable sampling of larval density. (3) The behaviour of larvae in the breeding habitats varies with the species. For the purpose of evaluating larval control measures, the follow­ ing precautions were taken and should ensure reasonably standardized samples: (a) Sampling was directed to sites where there are larval concentra­ tions in the breeding places. (This can be ascertained after a wide search for larvae). Those sites having a high density serve as fixed capture stations. (b) Depending on the local conditions, sampling was made with a ladle at Nima for small water collections and with a net dipper for large collections - as «* • . ' at Malam. It is observed in this project that the Culex quinquefasciatus population increases soon after the rains while C. thalassius increases during the rains and after, Table 20. A t Malam there was a very low University of Ghana http://ugspace.ug.edu.gh 101 number of Culex thalassius on the 24th June 1981 (i.e. 5) as compared with 1,970 on the 17,6.81 J(Table 19) This is explained by the very heavy rainfall registered on 23rd June 1981, as 68.6mm. (at Weija) Appendix a. This heavy rain resulted in the overflooding the banks of the pond at Malam with the result that almost all the mosquito populations were flushed to surrounding vegetation. Large numbers of Notoneeta followed and lasted for 4 weeks. The other aquatic organisms were mainly Cybister spp (larvae and adult), Gerris and Dragonfly nymph. All these aquatic organisms are predators and may explain the conti­ nuous absence of mosquitoes from 8.7.81 to 29,7,81 at Malam. (Table 19). There were unusually high numbers of pupae on the 4.3.81 and 8.4.81 at Malam (Table 19). This may be explained by a drop in 1st and 2nd instar larvae the last few weeks preceeding the dates, which in turn produced a lower number of 3rd-4th instar larvae on the respective dates 4.3.81 and 8.4.81. Unfortunately there were no numerical records but mere observations only. Another probable reason for the high number of pupae may be due to sustained high number of 3rd and 4th instar larvae in the weeks preceeding the 4.3.81 and 8.4.81. The usual lower number of pupae reflects the mortality pattern exhibited in the laboratory experiment on cohort analy si stables 1 1 and 1 2 j The dominant mosquito species at Malam is Cutex thalassius, A few other mosquito species emerged. They were C. deoens, C. dutton'i University of Ghana http://ugspace.ug.edu.gh 102 and C. quinquefasciatus but they were all eliminated after the 4.1.81. Aedes albocephalus emerged on the 6.5.81 but disappeared on the 20.5,81 when C. thalassius reappeared in large numbers. Measurements were made of the depth of the pond at Malam. There was a gradual decrease in depth from 2.5 metres on the 6.8.80 to 1.65 metres on the 25.2.81. However, it increased again to 3.1 metres jon 27/5/8*1 w h e n t h e r a n n s b e g a n . Unfortunately instars were not recorded for Malam until the 20,5.81 because interest was earlier directed towards Culex quinquefasciatus only. The survivorship curve for Nima (fig.5) based on the yearly total instars is not as expected. The value expected for the 1st and 4th instars larvae were 32,146 and 2;143 even though 6,964 and 2;677 were observed. The graphs figs. 3 and 6 depict that of the laboratory and Malam respectively. At Nima, two mosquito species coexisted throughout the year. They were Culex quinquefasciatus and C. tigripes. As Table 2.0 shows, their numbers rose to very high peaks before and after the rains. This could be explained by the fact that there is constant flushing during the rainy season which did not allow the mosquitoes to remain at one place. Another possibility may be due to the fact that Culex quinquefasciatus and C. tigripes larvae may thrive better in highly polluted environment. The sudden drop in numbers on the 18.2.81 and 5,8.81 (Table 20) may be due to the heavy rains registered on the 16.2.81 as 16.3mm and on 2.8.81 University of Ghana http://ugspace.ug.edu.gh 103 and 3.8.81 as 0.3mm, Appendix B. The population decreased considera­ bly between the 18,3.81 and 22.7.81 (Table 20). Many factors can determine the fate of a population. According to Andrewartha (1961b) there are 4 major factors as follows: food, climate, the action of other animals and pathogenic organisms, and living space. Subra (1970) studied the influence of these factors on Culex pipiens quinquefasciatus. One factor associated with crowding could have influenced the tank population of his study. Roubaud and Toumanoff (1930) first observed in the laboratory that the accumulation of toxic wastes excreted by larvae of C.p. pipiens could retard and even cause mortality among larvae. Subra (1970) tested for the possible effect of a toxic substance associated with the larval exuviae, but no significant effect could be found. Of all factors studied, the only demonstrable intrinsic factor was the toxic effect of the wastes of older larvae, which Hayes (1975) reported as being variable and operating for a relatively brief period. Very definite toxic effects of 3rd instar larval waste upon 1st instar larvae were demonstrated by Ikeshoji and Mulla (1970). In addition to production of toxic wastes, overcrowding, slowed down growth and development of younger larvae and produced morpho­ logical aberrations in larvae. Build-up of surplus food is associated with crowding. Excess food could induce microbial fermentation which, according to Subra (1970) University of Ghana http://ugspace.ug.edu.gh 104 would render the water unfit for the production of pupae. Subra contends that the larval habitat can become too polluted for Cm p. quinquefasciatus. Both microbial fermentation and larval waste products could have affected the laboratory population and cohort equally. The mortality in the laboratory population reared in beakers is partially attributed to crowding, which probably resulted in reduced feeding in some of the instars. Unfortunately, the weight of food (farex and ceralac) given in each group was not recorded. Crowding of immature stages is considered to be one of the main causes of migration or dispersal (Johnson 1966, 1969, Wada 1965). The studies of Nayar and Sauerman (1973) demonstrate that crowding of larval C. p. quinquefasoiatus resulted in increased flight activity of females. Such phenomenon could possibly have operated in the present study and might have reduced the number of females returning to the site to deposit eggs and therefore enhancing larval fluctuation. Very few investigations have been made into instar moralities of mosquito larvae, but in Nigeria and Kenya mortality of the pre-adults of Anopheles gambiae complex was greatest in 4th instar (Service 1971, 1973, 1976). in Bangkok, during the cooler months, mortality of Aedes aegypti was greatest in fourth-instar collected from water jars and ant traps, but in the hot season mortality was more intense in the first-instar in the water jars (Southwood et. al. 1972). However, in this experiment University of Ghana http://ugspace.ug.edu.gh 105 the highest mortality occurred between the pupae and adult stages with K-valup o. 24 Tablell. Under overcrowded conditions, older larvae of Culex pipiens Wiedeman elaborate chemicals known as 'overcrowding factors1 which are toxic to first-instar larvae and produce growth-retarding effects in young larvae (Hwang et. al, 1976). The same'overcrowding factors* is suspected to operate in this experiment* Probably this toxic effect could cause the mortality in the pupal stage which does not feed. The efficacy of natural enemies is higher when the biotype and the behaviour of larvae and predators favours close contact, for example, guppies Pftjecilia reticulata are surface feeders as are mosquito larvae, therefore the area of activity of the predator and the prey is the same. Predators which live at the bottom of the breed­ ing sites are less efficient. The smaller the volume of water in which the natural enemies and mosquitoes live, the more efficient the predator activity. The presence of other insects on which the predators feed reduces the impact of the predators on the mosquito population. For example, Notonecta and Cybister spp. larvae feed on other younger predators. Also at Nima, guppies may feed on Notonecta, Culex quinque- fasciatusj C. trigripes and younger larvae of Syrphidae - to mention a few. Also the efficacy of the predator varies with the environment which might increase or decrease the possibility and duration of contact between predators and mosquitoes. At Nima for example, there is quite University of Ghana http://ugspace.ug.edu.gh 106 a number of Notonecta, guppies, Culex tigripes and C. quinquefasibiatus but they all seem to live quite successfully in the water, even though it is expected that C. quinquefasciatus is preyed upon by the other predators. This may be due to the competitive exclusion principle whereby each of these organisms live at different zones in the environ­ ment (Boubjerg, 1970), The large numbers of C. quinquefasciatus compared with C. tigripes may be due to reproductive rate of C. quinquefasciatus. It is a well known fact that under the influence of environmental conditions a vector species may show changes in the seasonal distribu­ tion in the same area of dominance. The increase in density of a vector species is very much dependent on climatological factors favourable for its breeding, and adult survival. An exceptionally heavy rainy season might be favourable to the development of a number of species (e.g. Notonecta) yet detrimental to others (.e.g, the mosquito larvae). The climate is one of the major components of the physical environ­ ments, and is a composite condition of which temperature, relative humidity, precipitation, light and wind are the important components. The daily expression of climate is called "weather" and this has a profound impact on the biology, distribution and density of a mosquito species at any given time (Anon, 197 5a). The climate can be divided into 2 types. (i) macroclimate, which means the average weather conditions of an area, and (ii) microclimate, or modifications in restricted areas within the overall macroclimate zone. There are two major climates - wet and the University of Ghana http://ugspace.ug.edu.gh 107 dry season. It is therefore not enough to find the effect of climate on the mosquito incidence. However during the raining season the larvae are constantly flushed in the Nima drain (Table 20)but mosquitoes in the pond at Malam(Table 19)are not affected. Insects are cold-blooded and therefore all metabolis processes and the entire vital cycle depends on the environmental temperature. Mosquitoes, like the majority of insects are unable to control the body temperature of their bodies to a great extent. The insects can survive low temperatures but their metabolic processes are slowed down or even arrested when temperature falls below the threshold. Humidity can act as a limiting factor in distribution and longivity. Owing to the tracheal system of respiration, insects in general are parti cularly susceptible to dessication, even though forest species are more susceptible to humidity changes than those living in areas with dry climate (Anon, 1975a), The effect of rainfall varies according to its amount and the physical features of the terrain. Repeated rain causes severe flooding, resulting in temporary flushing out of the breeding places. Consequently the breeding of sc vector population is greatly reduced but it will soon be re-established when normal conditions are restored. Moderately frequent rainfall but with fairly long periods of sunshine will increase the opportunity for prolific breeding (Anon 1975a). University of Ghana http://ugspace.ug.edu.gh 108 Although circadian rhythms have been found to play an important role in controlling most mosquito activities (Anon 1975aj Hayes & Downs, 1980) the effect of light can generally be correlated with movement of mosquitoes for feeding or resting. Many species tolerate relatively wide temperature fluctuations, but extremes of heat or cold restrict the times and places where larvae can survive and thrive. Other physical and chemical factors that affect larvae and pupae include salinity, pH, hardnes of water, aeration, pollution, movement of water and light intensity. The i specific limits within which certain species tolerate such factors merit further investigation as aid to the better understanding of the occurrence and distribution of the species concerned. Temperature (especially minimum temperature) seems a good indicator for predict­ ing densities of a population of Culex pipiens quinquefasciatus (Hayes and Hsi, 1975). Knowledge of the ways in which the various physical and environ­ mental factors discussed in this project affect the immature stages of mosquitoes could certainly be utilized to design appropriate alterations of the environment. Such changes, effected by drainage, filling, removal of vegetation and shade, water-level fluctuation, or related measures, have been used successfully for reducing mosquito numbers. Because of their extremely important implications, they merit the most careful considerations from the earliest planning stage in any water management project (Anon, 1968). University of Ghana http://ugspace.ug.edu.gh 109 Life-Table analysis is needed in biological control for pre­ dicting population level. It is important in Life-Table to sample the population regularly throughout the season and to have a con­ tinuous record of reproduction and of mortality factors. This is more elaborate but not different in principle from the "index of population trend", suggested by Balch and Bird (1944). The life- table tells us what happened in a particular year but does not enable prediction of future changes, though it gives expectation for further life. When lx (Number of Population Surviving at age X) curves are compared, two important points emerge (i) The survivorship of animals in nature sometimes, but by no means always follows the J-shaped distribution (Pearl's 'Type B') resulting from extremely heavy morta­ lity at early stages. Diagonal lx curves (Pearl's 'Type B') are evidently frequent in natural as well as in laboratory populations (ii) the form of lx is strongly affected by its point of origin. Bird populations, for example, can be considered from the time the eggs are laid, from hatching, from fledgling, or from breeding age, and correspondingly different life-tables will result. The central requirement of life-table work is absolute population, estimation. As the fiducial limits of such estimates may be wide, it is a l w a y s of value, whenever possible, to make estimation by more than one method, this also helps to ensure that^aaj^^of tfce population University of Ghana http://ugspace.ug.edu.gh 110 is not totally overlooked. The internal consistency of the life- table provides yet another check on the reliability of the estimates. However, relative estimates are affected by so many factors that they are of limited use for the construction of a life-table. Since much of the previous work on mosquitoes has emphasized relative methods, studies aimed at the construction of a life-table will initially have to be based on techniques developed for other animals. The aims of such study will be to provide estimates of absolute population and to assess the density of the vector in relation to disease transmission and biting. In Constructing Survivorship Curves and Life-Tables of immature stages of a mosquito population, it is essential that all instars (age class) are sampled with equal intensity to ensure correct figures. However, it has been shown that, at least in some species, the degree of aggregation of the different larval instars and pupae differ con­ siderably, moreover they may occupy different parts of the habitat. Such behaviour will tend to bias the collection of various age groups in samples at the expense of the others. Moreover, it has been shown that, young instar larvae can remain submerged much longer than can older instars (because the younger instar can rely also on cuticular respiration). Consequently, when samples are taken at the water surface, the younger instar larval population will be under-estimated. The escape reaction of the instars may also differ. University of Ghana http://ugspace.ug.edu.gh Ill In this project, intensive work on Life-Tables was carried out both on the field and in the laboratory. Daily observations and records were made in the laboratory as presented in Table 14. are Detailed results / found in tables 15, 16, 17 and 18. The age dis­ tribution and survivorship curve of immature stages of Culex quinque­ fasciatus in the laboratory is presented in Figs. 3 and 4 and field experiments of C. quinquefasciatus and C. thalassius are in figs. 5 and 7, respectively. The summary for the data at Legon, Chorkor Lagoon, Malam and Nima are presented in Tables 3,4,6 and ^.respectively. Most of the values obtained were not what was expected. This may not be due to wrong sampling because it was actually observed on the field. On the other hand, it could either be attributed to aggregation of the • pupae or some unknown factors operating in the field. This may be explained by the fact that apart from Table 9 (Data from Nima) and Table 3 (Legon) the decrease is not in a constant trend of reduction. The data from Chorkor Lagoon (Table 4) show that on three occasions, there ware gradual trends in decrease. Emphasis was therefore laid on day 7-11 as found in fig.^ because it shows a uniform population reduction. Referring to Table 2 used to analyse the Life-Table, the observed values of 1st instar larvae and pupae of 8,087 and 1652 respectively were expected to be 16,517 and 2,870 respectively (Fig.9). University of Ghana http://ugspace.ug.edu.gh 112 At Malam, 1st instar larvae and pupae from day 5«1 5 were observed to be 36,440 and 1,587 respectively even though 62,797 and 12,530 were expected {Fig.8). At Nima between day 2-6 the respective values observed for 1st and 4th instar larvae were 17,0 69 and 4,963 even though 62679 and 3991 were expected respectively (fig.6). In these Life-Table studies, it appears that errors were found only in the first instars and late instar stages. At Legon Fig.10 the expected value for the 1st instar is 1469 and that for the 4th instar is 121. At Chorkor Lagoon, the expected value for the 1st instar is 53,831 , the value for the 4th instar is 6,325 and the pupae is 4,446. The expected values for Nima and Malam are illustrated on the graphs figs. 5 and 7 respectively. I wish to emphasize that the expected values obtained from the be graphs could/markedly affected by the accuracy of the experiment on duration of larval instars Tables 8 and 13. Slight errors in the duration of larval instar could affect the expeeted'- values. It is noted with quantitative support that the period of instar duration is affected by the temperature (Service, 1977). At big water bodies such as Chorkor Lagoon for instance, the values obtained for sampling are influenced by waves, unusual flooding and even by fishermen. It is therefore not surprising that the larval population decrease followed 3 trends (Tables 4): day 1-5, day 7-11 University of Ghana http://ugspace.ug.edu.gh 113 also and day 15-17. This fluctuation may/be due to addition of newly hatched eggs. The graph (Fig. 9) was plotted to represent day 7—11- The stages of an insect noraally provide the most powerful tool for analysing the seasonal changes in numbers. Moreover, if the relation of instar-length and temperature is determined experimentally, it will be possible to predict the mean lengths of the instars at the prevailing field temperatures by using the formulae of Davidson (1944). The methods of dealing with the determination of age structure and mortality have been devised by Dempster (1956). Richard and Waloff (1954) worked on population exposed to steady state. Traps based on the habit of larvae ascending to the surface have generally not given satisfactory samples of larval populations. Some traps have been designed to endorse a volume of water having a standard surface area; the contents of such traps can be removed and sieved. Alternatively, a base plate can be inserted into the submerged trap and the water allowed to drain away as the trap is removed. The available traps are not ideal, and new methods of collecting larvae are required. The light trap devised by Service (1981) and tried at Chorkor Lagoon and Malam is very efficient and should therefore be used for Life-Table studies. The effectiveness of the light and sticky traps were compared on the field at Chorkor Lagoon (Table 23) . In each case, the vari• ance (SD o ) is much greater than the mean(x—)(Table 25.) This shows that the difference between catches is not by chance of random distribution but as a result of difference in effectiveness of University of Ghana http://ugspace.ug.edu.gh 114 the traps. Unlike the sticky trap which is most efficient for pupae and younger instars larvae, the light trap is very efficient for all instars. Values obtained from experiments at Chorkor^ Table 23jconfirm this. In the laboratory 85% larvae in the sink were trapped with the light trap compared with 1 0% of the original pupae (Table 21). Experiment with the sticky trap in the laboratory gave 100% of trapped pupae and 60% of larvae, but the ratio of larvae to pupae in the sticky trap was 37:63 (Table 22). The light trap is therefore better for larvae while the sticky trap is efficient for pupae. Field experiments with light and sticky traps confirm the effi­ ciency of light trap for larvae and sticky trap for pupae (Table 24). However, light trap is more efficient for trapping mosquito larvae than the sticky trap. Field experiment with light trap shows that the ratio of larvae: pupae caught was 78:22 while the sticky trap gave a ratio of larvae: Pupae as 38:62 (Table 2^). Physico-chemical studies made at Nima and Malam^Table 26?show that Culex quinquefasciatus and C. tigripes prefer water with high pH i.e. slightly alkaline (pH 7.1- 8 .0 )whi‘l e C. thalassius prefers slightly acidic water i.e. (pH 3.2-6.9) and high sodium (Na+) and chloride ion (Cl“) contents. Also C. thalassius thrives in the soil of a higher organic matter content, as compared with C. quinquefasciatus and C. tigripes (Table 27) University of Ghana http://ugspace.ug.edu.gh 115 One should bear in mind that the chloride content fluctuates from time to time and is much influenced by the rain. Strictly speaking, one cannot compare the values of the 2 sites - Nima and Malam. Apart from the differences in sampling methods, Nima is a drain while Malam is a pond. Culex quinquefasciatus breeds at Nima while C. thalassius breeds at Malam. The difference in sampling method could equally affect the results of the Life-table. The relationship between rainfall, Relative Humidity, temperature and period in months over the past 7 years has been represented in the graph -i^pen-Lices C & D#^pp. E represents the data throughout the period of study at Nima. The objectives of insecticide susceptibility tests are: (1) To establish baseline susceptibility level of larvae in areas wherelarviciding has to be applied. (2) To detect any change in susceptibility level of larvae in areas where larviciding is applied correctly but larvae are still found. Larvae of Culex pipiens quinquefasciatus are less susceptible to DDT than are most other Culicines such as Aedes aegypti. The lowest LC50 values for C.p. quinquefasciatus were recorded for laboratory strains - viz; 0.0 25 ppm for a colony bred strain at Lagos, Nigeria (Elliot 1955) and 0.0 3 ppm for a Rangoon strain selected for suscepti­ bility (Tanado and Brown 1967). The lowest LC50 of DDT found in wild University of Ghana http://ugspace.ug.edu.gh 116 strain were 0.04 ppm at Maracay, Venezuela (Blazquez, 1958), 0.045 ppm at Visalia, Calif (Gjullin and Peters 1952) and 0.045 at Tampin, Malaya (Wharton, 1955) ; on one of the many samples taken at Rangoon, Burma, showed an LC50 as low as 0.0025 ppm (Rosen, 1967). Moreover, this species breeds in polluted water, in which it is more difficult to kill the larvae with DDT (Hurlbut and Bohart, 1945), the mortality decreasing as the concentration of total solids increases (Parthasarathy and Kruse, 19541 In Malaya, Reid (1955) was unable to control C. p. quinquefasciatus larvae in drains at Klang and Kuala Lumpur even with DDT at 2.25kg/ha, the abundant organic matter undoubtedly being partly responsible (however, both HCH and dieldrin were effective). In British Guianaj Giglioli (1948) could not obtain a persistent effect with DDT in pit latrines at Lodge Village, near Georgetown. Repeated experimental results on susceptibility of C, quinquefasciatus to DDT, DIELDRIN and LINDANE in this project in Tables 28, 29 and 30 and Figs. 1$, 12, 13 respectively show that the LC50 of DDT is 0.040 ppm and LC95 = 2.20ppm. The upper and lower confidence limits for LC5Q are 0.059 ppm and 0.027 ppm, while the upper and lower confidence limits of LCg5 are 4.156 ppm and 0.779 ppm. The LC50 and LC95 for DIELDRIN are 0.019 ppm and 1.80 ppm respectively. The upper and lower confi­ dence limits for LC50 are 0.009ppm and 0.036ppm while the upper and lower confidence limits for LC95 are 0.779 ppm and 4.156 ppm respectively. Tables 31, 32 and 33 give data on susceptibility of DDT, DIELDRIN and LINDANE respectively. They explain the fitting of regression line University of Ghana http://ugspace.ug.edu.gh 117 and testing the goodness of fit. The LC50 and LCg5 for LINDANE are 0 .025 ppm and 2.10 ppm respectively. The upper and lower confidence limits for LC50 are 0.04 3 ppm and 0.014 ppm while the upper and lower confidence limits for LC95 are 5.134 ppm and 0.859 ppm. Apart from probable errors that could affect the results of the susceptibility tests, improper mixing of the insecticides could also affect the results. However, there is evidence to show that Cutex quinquefasc'iatus has developed resistance to all the insecti­ cides tested - DDT, DIELDRIN and LINDANE. Discriminating dossage from probit analysis (Fig. 14) of lppm gave about 80-98% (81-87% av.) mortality in each case.(4£ A T H A . H • t , . (l 4 &. ( b j h> c( *JS pcp~l<-*> s* ANONYMOUS (1953) First progress roef pCo1r. 1tU 5o0f /m’ ►onsqj ui2t-2or i Cifnvestigations. Milk River Irrigation Project, Montana (with particular reference to causes of mosquito production in long- established irrigated area characterized by flat topo­ graphy and heavy soils). Communicable Disease Center, U.S. Public Health Service HEW, in cooperation with Montana State Board of Health and Montana Agric. Exp. Sta. Mimeo. 53 pp. ANONYMOUS (1968) WHO Technical Report Series 368: 5-22. ANONYMOUS (1975a) Larval Surveys. Manual on Practical Entomology in Malaria. Part 1 160pp, - Prepared by the WHO division of Malaria and other parasitic diseases. ANONYMOUS (1975b) Larval Surveys. Manual on Practical Entomology in Malaria Part II 191pp. - prepared by the WHO division of Malaria and other parasitic diseases. ANONYMOUS (1970) WHO Expert Committee on Insecticides. Seventeenth Report, Geneva WHO Technical Report Series No. 443 Annexes 1A and IB. ANONYMOUS (1978) WHO Chronicle 32: 33-344. BALCH, R.E., and BIRD F.T. (1944) Sc. Agri. 25: 65-80. BATES, M. (1941) Field Studies of anopheline mosquitoes erf -Ĵ TBania. Proc. Ent. Soc. Wash. 43, 37- University of Ghana http://ugspace.ug.edu.gh 126 BEVERTON, R.J.H. and HOLT, S. J. (1957) 'On the Dynamics of Exploited Fish Populations.’ Fishery Investigations, Ser. 2 19:533.pp. Min. Agric. Fish Fd. London, HMSO. BLAZQUEZ, J. (1958) Indian J. Malar. 12: 323-329. BOUBJERG, R.V. (1970) Ecological isolation and competitive exclusion in crayfish (Qrconectes viridis and Qrconectes immunis) Ecology 51: 225-236. BOYD (1949) Malariology W.B. Saunders Co., Phildelphia, Pa Vol. 1 787 pp. SUENETT G.F. & ASH, L.H. (1961) The Susceptibility to Insecticites of Disease - carrying Mosquitos in Fiji, Bull. Wld. Hlth. Org. 24: 547-555. = CAMBOURNAC, F.J.C. (1939) A method for determining the larval anopheles population and its distribution in rice fields and other breed­ ing places. Riv. Malariol 18, 17- CHINERY, W,A. (1965) Observations of mosquito breeding in Accra. Ghana Medical Journal 4: 164-165. CHINERY, W, A. (1968a) A Survey of Mosquito breeding in Accra, Ghana, during a 2-'year period of larval mosquito control. Ghana Medical Journal 8(4): 266-274. CHINERY, W.A. (1968b) Mosquito Control in an Urban environment with reference to the anti-mosquito operations in Accra and Tema. Ghana Medical Journal % ' 7(4) • 205-208. CHRISTIE, M. (1954) A mothod for the numerical study of larval popula­ tion of Anopheles gambiae and other pool-bredding mosquitoes. Ann. Trop. Med. Parazit: 48: 271-276. DAVIDSON, J. (1944) J. Anim Ecol. 13: 26-38, DE MELLON, B.A., SEBASTIAN and Z.H. KHAN (1967) Time of arrival of gravid Culex pipiens fatigans at an oviposition sit^, the oviposition cycle fcnd the relationship between, time of feeding and time of oviposition. Bull. Wld. Helth. Org. 36: 39-41 DEMPTER, P. , (1956) J. Anim. Ecol. 25: 1-5. ELLIOTT, R. (1955) Trans Roy Soc. Trop. Med. Hyg. 49: 528-542. GIGLIOLI, G. (1948) Malaria, filariasis and yellow fever in British Guina. Bristish Guina, Medical Department, Mosquito Control Services. University of Ghana http://ugspace.ug.edu.gh 127 GJULLIN, C.M. and PETERS, R,F. (1952) Recent studies of Mosquito Resistance to Insecticides in Califonia, Mosquito News 12: 1 - 7, GOODWIN, M.H. and EYLES (1942) Measurements of larval populations of Anopheles quadrimaculatusf Say Ecology 23: 376,-- GRAHAM, W.M, (1910) Results obtained from a monthly examination of the native domestic water - receptacles at Lagos, Southern Nigeria, in 1910-11, Bull. Ent. Res. 2:127-136, HAMON, J. et al (1958) Bull, Soc. Path, Exot,, 51: 393-400. HAYES, J. and DOWNS, T,D. (1980) Seasonal changes in an isolated population of Culex pipiens quinquefasciatus (Diptera: Culicidae), A time Series analysis, J. Med. Ent. 17 (1) : 63-69, HAYES, J. and HSI, B„Pt (1975) Interrelationships between meterologic phenomena and immature stages of Culex pipiens quinque­ fasciatus Say; Study of an isolated population. J. Med, Ent, 12(3) 299-308, HAYES, J. (1975) Seasonal changes in population structure of Culex pipiens quinquefasciatus Say (Diptera Culicidae) ,* J. Med~. Ent. 12 (2) : 167-178. SuTf 4 s ■ g* 6 6c tt A £.m(,<^5) X Been $8 ' 7.ZS- HWANG, Y.S., MULLA, M.S., ARIAS, J,R, and MAJORI, G, (1975) Overcrowding factors of mosquito larvae VII, Preparation and biological activity of methyloctadecanes and methylnonadecanes against larvae. J. Agric, Ed. Chem 24: 160-3. IKESHOJI, T. and M.S, MULLA (1970) Overcrowding factors of mosquito- larvae. J. Econ. Ent. 63: 90-96. JOHNSON, C.G. (1966) A functional system of adaptive dispersal by flight. Ann. Rev« Ent, 11: 233-60. JOHNSON, C.G. (1969) Migration and dispersal of insects by flight. Methuen and Co, Ltd. London 763 p, LAKHANI, K.H, and SERVICE, M.W. (1974) Estimated mortalities of the immature stages of Aedes cantans (Meigen) (Dipt. Culicidae) in a natural habitat. Bull. Ent. Res, 64: 265-276. LITCHFIELD, J.T. and WILCOXON, F. (1949) A simplified method of evaluation dose-effect experiments, J, Pharmacol- exp . Ther, 96:99,- University of Ghana http://ugspace.ug.edu.gh 128 MACFIE JWS AND INGRAM A (1961) The domestic mosquitoes of Accra Bulletin of Entomological Res. 7: 161-177, MORRIS, R.F. (1963) Predictive population equations based on Key factors. Men, ent. Soc. Canada 32: 16-21. NAYAR, J.K. and D.M. SAUERMAN, J,R. (1973) A comparative study of growth and development in Florida mosquitoesPart 4, Effects of temporary crowding during larval stages on female flight activity patterns. J. Med. Entf 10: 37-42, PARTHASARATHY, T. and KRUSE, C.W. (1954) Indian Malar. 33-46, PATTERSON, R.S., D.E. WEIDHAAS, H.R. FORD and C,S. LOFGREN (1970) Suppression and elimination of an island population of Culex pipiens quinquefasciatus with sterile males. SCIENCE 168: 1368-70, REID, J.A, (1955) Resistance to Insecticides in the larvae of Culex fatigans in Malaya. Bull. Wld, Hlth. Org. 12: 705-710, RICHARDS, O.W. (1961) and WALOFF, N. (1954) Anti-locust Bull. No. 17: 182 pp. RICKER, W.E. (1944) Further notes on fishing mortality and effort Copeia 1944; 23-44, RICKER, W.E. (1948) 'Methods of Estimating Vital Statistics of Fish Populations, 1 Indiana Univ, Publ. Sc, Ser. 15, 101 pp. ROSEN, P. (1967) The susceptibility of Culex pipiens fatigans larvae to insecticides in Rongoon, Burma, Bull. WHO 37; 301-310, ROUBAUD, E. and TOUMANOFF, C, (1930) Intoxications d ?encombrement, chez les larves de CElex vivant en milieus non renouvele. Bull. Soc. Path. Exot, 23: 978-86. SERVICE, M„W, (1971) Studies on Sampling larval populations of the Anopheles gambiae complex. Bull. Wld. Hlth. Org. 4-5':169-80. SERVICE, M „W . (1973) Mortalities of the larvae of the Anopheles gambiae Giles Complex and detection of predators by the precipitin test. Bull. Ent. Res. 62: 359-69, University of Ghana http://ugspace.ug.edu.gh 129 SERVICE, M.W. (1976) Mortality of the ajnrSaWre stages of species B of the Anopheles gambiae Complex in Kenya; Comparison between rice fields and temporary pools, identification of predatory and effects of insecticidae treatment, J. Med. Ent, 13; (in press) SERVICE, M.W. (1977) Journal of Applied Ecology 14; 159*-'196, SERVICE, M.W. (1981) Aquatic light Traps. Personal Communication, SOUTHWOOD, T.R,E, (1966) Ecological Methods with Particular Reference to the Study of Insect Population, Methuen, London. X IV -391 p p . SOUTHWOOD, T.R.E,, MURDIE, G. , YASUNO, M,, TOWN, R.J, and READER, P.M. (1972) Studies on the life budget of Aedes aegypti in Wat Saraphaya, Bangkok, Thailand. Bull, WHO 46: 211-26. SOUTHWOOD, T.R.E. (1978) Ecological methods Lond, Methuen, SUBRA, R. (1970c ) Contributions to the biological and ecological Study of Culex pipiens fatigans Wied., 1928 (Dipten; Culicidae) in an urban zone of the West African Savannah, Dynamics of preadult populations, WRO/VBC/70, 193 (Mimeo), TANADO, T, and BROWN, A,W»A, (1967) Genetical Linkage Relationships of DDT-Resistance and Dieldrin - Resistance in Culex pipiens fatigans Weid, Bull. Wld, Hlth. Org, 36: 101-111. VARLEY., G.E, and GRADWELL, G,R« (1970) Recent advances in insect population dynamics, A Rev, Ent. 15; 1-24, WADA, Y. (1965) Overcrowding of Culex pipiens Complex in relation to dispersal, WHO Vector Control/125, 65; 119-25 (Mimeo), WEIDHASS, D.E,, R.S, PATTERSON, C,S. LOFGREN and H.R. FORD(X971) Bionomics of a population of Culex pipiens quiquefasciatus Say. Mosquito News 31: 178-82. WEIDHASS, D.E., B.J, SMITTLE, R.S. PETTERSON, H.R, FORD and C.S. LOFGREN (1973) Survival, reproductive capacity, and migration of adult Culex pipiens quinquefasciatus Say. Mosquito News 33: 83-87, WHARTONf R.H. (1955) The Susceptibility of Various Species of Mosquito to DDT, DIELDRIN and B.H.C, Bull. Ent, Res. 46: 301-309. WOHLSCHLAG, D,E, (1954) Mortality rates of Whitefish in an ar.tic lake. Ecology, 35; 388-396, University of Ghana http://ugspace.ug.edu.gh 130 9. A P P E N D I C E S . APPEND IX A DAILY RECORD OF R Al NFA L L (mi l l imerres) AT WEI JA AT LA T IT U D E 5 ° 3 4 / N, LONGITUDE 0 ° 2 I 'W . AND A LT ITU D E 71 M E T R E S AS O BSERVED DURING T H E PER IOD OF STUDY AT M A L A M , 6 T H A U G U S T , 1980 THROUGH 5TH AUGUST, 1981. 1980 1981 Dote Aug. Sep. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May Jun. Jul . Aug. mm. mm. mm. m m . mm. mm. mm. mm, mm. mm. mm. mm. mm. 1 2 21-6 3 - 4 19-3 5 1 0 6 4 ■ 1 7 26-4 11 *9 8 47-5 9 32-8 24*6 10 4-6 21-8 16 8 1 1 42-2 12 8-1 13 35-1 45-2 14 1 5 1 6 9-7 17 18 19 21 6 20 15-5 2 1 7-1 1 0 22 23 23-9 7* 4 68-6 2 4 2 5 4-1 4-6 2 6 5-3 59 9 2 7 2 5 2-7 4 0 2 8 2 9 X X 3 0 24-1 X X 3 1 X X X X X X X X X X Totals(mm) 85-4 64-3 41-4 0 2-7 0 20 1220 i 1659 24-6 Days with 0- 2 mm 4 6 3 0 1 0 2 9 6 3 or more Days with 1*0 mm 4 6 3 0 1 0 2 9 6 3 or more University of Ghana http://ugspace.ug.edu.gh APPENDIX B DAILY RECORD OF R A IN F A L L (mi l l imetres) IN ACCRA AT LA T ITU D E 5° 36' N. LONGITUDE 0° 10' W. AND A L T IT U D E 67 M ETRES AS OBSERVED DURING T H E P E R IO D OF STUDY AT N IM A , IOTH S E P T E M B E R , 1980 THROUGH 9 TH S E P T E M B E R , 1981. 1 9 8 0 1981 Date Sep. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Se p. m m. mm. m m, m m . mm. m m. mm. m m . mm. m m . mm. mm. mm. 1 8 9 2 3-1 15-0 0-3 3 2 3 9 2 3 0 3 4 0-5 14-8 1 -3 5 1 3 6 3-3 1 80 4 3 0-5 3 0 0-3 7 1-5 2-5 15-7 60-8 18-8 8 5-1 9 7-9 1* 1 0-5 10 24-6 16-8 0-3 ! 1 2 3 1 2 1 -3 5 8 16-5 13 46-5 3-8 44-7 14 1 5 0-8 6 3 1-5 0-3 30 9 16 0-8 0 8 6-3 1 7 1 0 0-3 0-5 2 3 1 1-5 24 4 1 8 7 9 29 0 1-8 0-5 1 9 1-3 13-5 3-8 3-8 7 6 2 0 8-4 5 4 2 1 3-0 22 6 6 1 19 0 0-3 2 2 3 1 2 5 16-0 0 8 2 3 1-5 24-9 2 4 2 5 1-0 2 5 8 9 1-1 3 1 0-3 2 6 1 -6 2-0 14 9 2 7 12-9 15 3 4 6 3- 1 2-8 2 8 29 X X 30 X X 3 1 X X X X X X X X X X X X Tota!s(mm) 76 0 45 4 7-3 2 0 114 39 3 23-4 140-2 144 G 84 0 56-9 Days with 0 2mm 1 1 5 2 1 2 5 4 14 12 12 6 or more Days with I 'Omm 9 5 2 1 2 4 4 12 10 8 2 or more University of Ghana http://ugspace.ug.edu.gh 132 ENDIX G 2 4 0 220 200 180 160 140 L> 120 100 80 60 40 20 0 EAN M AX .- M E A N MIN. T E M P E R A T U R E , E L A T I V E HUM ID ITY A N D R A IN F A L L AT 'El J A 1970- 1977 ( Average) University of Ghana http://ugspace.ug.edu.gh 133 D 2 4 0 2 20 200 160 160 140 I■ 120 * 100 80 60 4 0 20 0 MEAN MAX. - MEAN MIN. TEMPERATURE RELAT IVE HUMIDITY AND R A IN F A L L AT ACCRA 1970- 1977 (Average) University of Ghana http://ugspace.ug.edu.gh 134 appendix e 1980 1981 MEAN MAX. - MEAN MIN. T E M P E R A T U R E , R E L A T IV E HUMID ITY AT 0 9 0 0 H R S AND R A IN F A L L IN ACCRA SEPT. 1980 - AUGUST 19 8 11 Refer to A pp B )