Oviposition in aphidophagous ladybirds: effect of prey availability and conspecific egg presence

Oviposition site selection in ladybirds is a dynamic process influenced by a number of abiotic and biotic factors. In this study we investigated whether prey quantity and egg presence (varying in relatedness and age) influence oviposition behavior in the zigzag ladybird, Menochilus sexmaculatus (Fabricius). Influence of these factors on cannibalism by females was also investigated and we tried to observe whether cannibalism was a modifying mechanism during oviposition site selection. Females were placed in prey abundant or scarce conditions in presence of related or unrelated eggs of varying ages, and their oviposition (for 24 h), egg viability and cannibalism were recorded. Prey-scarce conditions significantly decreased oviposition but had no influence on egg viability. Prey scarcity also increased the incidence of cannibalism by females. Females avoided laying eggs in the presence of related eggs regardless of their age. On the other hand, cannibalism was more in related eggs that were older in age. This increased cannibalism in presence of older related eggs, may be a comprehensive way of eliminating potential competition threats from a potential oviposition site already having eggs. All the independent factors (prey quantity, egg relatedness and egg age) did not affect egg viability, is the suggestive of male nutritional status rather than female.