Variation in egg and adult production of Callosobruchus maculatus (F.) and Callosobruchus chinensis (L.) and the effect of egg density and oviposition site limitation

Abstract

Variation in egg and adult production in Yemen and Brazil strains of C. maculatus and Indonesian strain of C. chinensis was investigated on cowpea {Vigna unguiculata (L.) Walp), greengram (Vigna radiata (L.) Wilczek) and adzuki beans {Phaseolus angularis (Willd) Wight). Seed density and the host species influenced the egg and adult production of these strains to varying degrees. The decline in egg production was most notable in C.maculatus Yemen strain when the host seeds available for oviposition was limited. However, the egg production of Brazil strain of C.maculatus and the Indonesian strain of C. chinensis was not affected significantly by the seed size or seed density. Larvae of C. maculatus Yemen strain face more intense competition within the seeds due to their larger body size. Thus the females of C. maculatus Yemen strain tend to load eggs in relation to seed size and seed density, thereby regulating the larval competition and maximizing the individual fitness. Of the three host species, cowpea is the most suitable food substrate for adult production. The females emerged from adzuki beans were lower in body size indicating its inferiority as a food substrate.