The biology of the kola weevil Balanogastris kolae on Cola acuminata and Cola verticillata

Abstract

Studies on aspects of the biology of the kola weevil Balanogastris kolae on Cola acuminata and C. verticillata were made in the laboratory at temperatures of 28–30°C. Mated females of B. kolae oviposited a significantly higher number of eggs (238) in C. acuminata than in C. verticillata (205) when confined separately with the nuts. But when the weevil was offered the choice of three Cola species as oviposition media, significantly more eggs were oviposited in both C. nitida and C. verticillata than in C. acuminata . However, there was no significant difference between the number of eggs oviposited in C. verticillata and C. nitida . The average total incubation, larval and pupal developmental periods of B. kolae in both C. nitida and C. verticillata were 6, 16.2 and 6.1 days, respectively. The average total developmental period in C. acuminata was 28.8 days, and 26.5 days in C. verticillata . Although the total developmental periods overlap, there was a significant difference between the periods of development of B. kolae in the two Cola species. Oviposition and development of B. kolae in the wild species, C. verticillata , coupled with its wide distribution show that it may be ecologically important in the survival of the weevils, especially when the cultivated Cola species are not available in the field.