Observations on Oviposition Decisions by Females of a Nigerian Population of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae).

The oviposition behaviour of a Nigerian population of Callosobruchus maculatus (p.) when presented with seeds bearing different egg-loads, was observed
under ambient laboratory conditions in Akure, Nigeria. Data obtained were analysed to distinguish two strategies by which females prefer pristine seeds or seeds bearing relatively few eggs for oviposition. The first is a relative rule in which a female compares the seed she is currently inspecting with a memory trace for the seed(s) visited previously. The second is an absolute rule in which the female responds only
to the current egg load on a seed, but where each increase in egg-load corresponds to a lower probability of acceptance. It was concluded that C. maculatus utilises both rules in egg laying decisions depending on the disparity in egg density of the seeds. When the largest difference between the number of eggs on any two seeds was low (4 or less), the relative rule prevailed; but when the difference was high (up to 6 or 8), the C absolute rule applied. Data were also provided which indicate that obscured eggs borne in part of seed in close. contact with floor of Petri plate) were not processed during egg-load assessment by C. maculatus females.

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