Intraspecific and interspecific competition in Callosobruchus maculatus (F.) and Callosobruchus subinnotatus (Pic) on stored bambara groundnut, Vigna subterranea (L.) Verdcourt.

Intraspecific competition was studied in Callosobruchus maculatus and Callosobruchus subinnotatus. Interspecific competition between the two bruchids was also studied to determine which of these species is likely to cause more damage to stored bambara groundnuts, Vigna subterranea in cases of joint infestation. Results showed that increasing the adult density up to 8 females per 10g of bambara groundnut seeds did not significantly reduce the mean number of eggs laid per female, the number of eggs developing to the adult stage, or the weight of emerged adults of either species. The developmental period of the two species was also not significantly affected. The adult emergence curve of C. maculatus was similar to that of C. subinnotatus and was of the scramble type. C. maculatus performed better than C. subinnotatus in interspecific competition and it achieved this through a higher egg-laying ability and a higher rate of progeny production coupled with a shorter life-cycle. The implications of these findings with respect to damage and possible loss of stored bambara groundnut are discussed.