Effect of dietary history on intraguild predation and cannibalism of ladybirds' eggs

Dietary history during immature development has a major influence on the evolution of food choices of aphidophagous ladybirds. We designed laboratory experiments to investigate the influence of consuming conspecific eggs or heterospecific eggs as the only food during larval development on the food choice of adult aphidophagous ladybirds, viz. Propylea dissecta (Mulsant) [Pd], Coccinella septempunctata L. [C7] and Menochilus sexmaculatus (Fabricius) [Ms]. We provided conspecific eggs and heterospecific eggs in presence of fewer aphids, Aphis craccivora (Koch) for 24-h to the adult males of the three ladybird species that were previously reared on monotypic conspecific or heterospecific egg-diet to determine their food choice. All ladybirds preferably consume aphids. However, amongst different egg-diets, mostly ladybirds prefer to feed on the same egg-diet, which they had consumed during the larval stage. Contrarily, C7 raised on conspecific eggs preferred different egg-diet (Pd eggs) than the same one. Furthermore, C7 reared on heterospecific eggs consumed these eggs more readily during adulthood than the conspecific eggs. This explains why C7 dominates coccinellid fauna, as an invader and an intraguild predator, in various geographical habitats. We concluded that prolonged exposure to unnatural diets, such as coccinellids' eggs during immature development, tend to develop a craving for such diets during adulthood of ladybirds.