Host preference of Callosobruchus maculatus: a comparison of life history characteristics for three strains of beetles on two varieties of cowpea

The reproductive success of Callosobruchus maculatus Fabricius, the main insect pest of stored cowpea, may vary between strains of this beetle and between varieties of the host seeds. Life history parameters of beetle strains from three different origins in West Africa were compared on two susceptible varieties of cowpea, Vigna unguiculata (L.) Walp. All beetle strains were assayed in a no-choice and a two-choice test. No major differences were found between the beetle strains. In a no-choice situation, the developmental period from egg to adult was prolonged on the bean variety Kpodjiguegue. In a two-choice situation, the beetles showed a strong preference for the Californian blackeyed bean variety to oviposit on. Here again the development took longer on Kpodjiguegue beans and the intrinsic rate of increase of the beetle population was lower. Using either equal numbers of beans of the same size or equal weights of beans of undetermined size of the two bean varieties did not affect the outcome of the test.