Life history of flight morph females of Callosobruchus maculatus F.: evidence of a reproductive diapause

Abstract

Callosobruchus maculatus (F.) (Coleoptera : Bruchidae) is a tropical beetle that develops in the seeds of Vigna unguiculata. C. maculatus adults show an imaginal polymorphism with differences in morphological, behavioral and reproductive characteristics. Adults of the flight morph that emerge in cowpea storage systems were studied under natural climatic conditions. A large number of the flight morph females were in reproductive diapause and had a long imaginal life. These females did not synthesize vitellogenin, produced a specific diapause protein and possessed significant protein reserves. This suggests that the beetles survived in the tropical ecosystem for a long time and colonized the crops during the cowpea growing and flowering phases. Analysis of reproductive activity in females captured in the V. unguiculata crops indicates that they terminated their reproductive diapause and began to lay eggs as soon as the pods were formed. Few females of the flight morph were sexually active at the beginning of imaginal life. In this paper we discuss the adaptive significance of these two reproductive strategies in females of C. maculatus.