Seed-Coat Colour Affects Oviposition in the Bean Beetle, Callosobruchus maculatus (Coleoptera: Chrysomelidae)

Abstract

Bean beetles (Callosobruchus maculatus) are known to evaluate their host quality and texture of seed coat. However, the effect of seed-coat colour on oviposition decision has remained unclear. Cowpea seeds, in which white and brown areas are equals in size, were chosen for oviposition decision tests. Females laid more eggs onto the brown than white area under both low and high beetle densities. However, in high beetle density, females distributed their eggs more uniformly onto both areas, i.e. high beetle density reduced the preference for the brown area probably to reduce competition among the offspring, and females also dumped some eggs. An additional test with sheets of paper covered with white and brown squares in the chessboard pattern showed that females laid more eggs onto brown than white areas. In conclusion, seed coat colour and beetle density affect oviposition in the bean beetle.