The Bionomics of Diopsis (Dipteral Digpsidae) and of Epiiachna Similis (Coleopteba, Coccinellidae) on Oryza Sativa L. in the Accra Plains

Abstract

The biology of Siopsis species (Diptera; Diopsidae) and Epilachna s im i l is (Coleoptera; Coccinellidae) was studied on the Acora P lain s . of the three species of Diopais found, D. thoracica caused the most severe damage to r i c e . AH the developmental stages of these insects are described and keys are provided for identify in g a ll the various stages of the Diopsis species. D. thoracica exhibits sexual dimorphism with regard to the interorbita l distance. A high stalk infestation o f forty -eight per cent was recorded in the major rainy season. The parasite and alternate host of these insects species are discussed. Artificial infestation of rice stalks with the larvae o f D. thoracica demonstrated that a single larva, could destroy 3 - 6 stalks during its life time leading to a loss of about nine percent in yield . All the developmental stages o f B. similis are described and a key provided for identify in g the four larval in s tars . Possible control measures against the Diopsis species and Epilachna similis are discussed.