Plasticity in the Egg-Spacing Behavior of a Seed Beetle: Effects of Host Deprivation and Seed Patchiness (Coleoptera: Bruchidae)

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Journal of Insect Behavior



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Egg-laying females of the seed beetle Callosobruchus maculatusdiscriminate between egg-free and egg-laden seeds and produce a nearly uniform distribution of eggs among seeds. We examined plasticity in this trait in response to both an internal factor (level of host deprivation) and an environmental one (the spatial configuration of available seeds). Responses to each factor were measured in genetically divergent strains that show a relatively strong (S strain) or weak (B strain) tendency to spread eggs evenly among seeds. Following a modest (10-h) period of host deprivation, S-strain females distributed their eggs less uniformly among seeds; the proportion of females committing at least one oviposition “mistake” increased from 20 to 50%. Similarly, S-strain females distributed their eggs less uniformly if seeds were presented in multiple, discrete patches instead of in a single, large patch. The higher frequency of oviposition mistakes in the multiple-patch arena was caused in part by females maintaining a uniform distribution of eggs within patches but not among patches. In contrast, females from the “sloppier” B strain were unaffected by either host deprivation or resource dispersion. Responses to seed patchiness are discussed in relation to the role of learning in the egg-spacing behavior of C. maculatus.

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