The effect of male sodium diet and mating history on female reproduction in the puddling squinting bush brown Bicyclus anynana (Lepidoptera)
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The males of butterflies transfer a spermatophore to the female during mating that can contain nutrients enhancing the reproductive potential of their partners. The nutrients transferred by males can be derived from both larval and adult feeding. These nutrients may be depleted by multiple matings. An apparent difference in adult feeding behaviour between the sexes is puddling on mud, dung and carrion, which in most butterfly species is exclusively a male behaviour. A possible explanation for this division in feeding behaviour is that nutrients derived from puddling by males are transferred to the female during mating. Here, we test this hypothesis in the African fruit-feeding butterfly Bicyclus anynana. We varied the male nuptial gift by (1) feeding males either a diet with or without sodium, and (2) varying the number of previous successful copulations by remating males up to five times on consecutive days. The results show both a strong effect of order of mating on the mating duration, and an individual effect with some males typically copulating for a shorter time than others. The effects on female reproduction were, however, minimal. The total number of eggs per female and the sodium content of the eggs did not differ significantly between diets, nor were they affected by the mating histories of the males. Eggs showed a non-significant lower hatching for females partnered by a male who had already mated several times. There was an indication of an interaction with male diet: the sodium treatment showing a decline in egg hatchability with order number of male mating, whilst the control treatment showed a constant hatchability. The results are discussed in relation to determinants of male gift-giving strategy and to other potential explanations for a restriction of puddling to males in butterflies.