The parent stock of C. maculatus used for this study was obtained from the Entomology Research Laboratory, Department of Crop Protection and Environmental Biology, University of Ibadan, Nigeria under the ambient temperature of 27+ 2 0 C and 78+5% relative humidity. 250 g of cowpea seeds were weighed into two 1 Litre Kilner jars and thirty adult C. Maculatus (1male:1 female) were introduced into the jars and kept in the laboratory for three weeks for the insect to mate and lay eggs. New cohorts of beetles that emerged were later introduced into the clean disinfected jars containing cowpea in the laboratory and the culture of insect was maintained throughout the experiment.