A TECHNIQUE FOR HANDLING AND SEXING CALLOSOBRUCHUS-MACULATUS (F) ADULTS (COLEOPTERA, BRUCHIDAE)

A simple technique for easy sexing and handling of the cowpea weevil, Callosobruchus maculatus, adults cultured on cowpea seeds without subjecting them to chilling, anaesthesia or microscopic observation, is described. The beetles were collected by inverting the clear-plastic rearing container with a pipette inserted through the lid under a light source. The enclosed weevils moving towards the light source were easily sexed by the shape and size of the abdomens, that of the male being shorter, with the dorsal side of terminal segments curved sharply downwards, as compared with the female. Beetles were collected into the pipette by nudging them off the container wall to obtain the desired number and sex ratio. A comparison with chilling and anaesthetization methods showed that for chilling in particular, there was some mortality of the weevil. This time-saving method can be used for sexing and collecting other Callosobruchus species.