Do more food choices lead to bad decisions? A case study in predacious ladybird beetle, Propylea dissecta.

Abstract

Understanding why animals choose one food over another is one of the key questions underlying the fields of behaviour ecology. This study aims to test if ladybird beetles, Propylea dissecta Mulsant (Coleoptera: Coccinellidae) can forage selectively for nutrients in order to redress specific nutritional imbalances to maximise their fitness. The general approach was, first, to manipulate the nutritional status of the predator by rearing them in five separate pre-treatment dietary groups from first instar larvae to newly emerged adult stage. Thereafter, we tested their feeding response to five different types of food, i.e., Aphis craccivora Koch, Aphis nerii Boyer de Fonsclombe, conspecific eggs, heterospecific eggs and mixed pollen grains, equidistantly placed in Petri dish. On the basis of newly emerged adults food choice, they were reared on the same diet for 10 days. Thereafter, adults were paired with their opposite sex (collected from stock culture reared on A. craccivora) and mating and reproductive parameters were recorded. Our results suggested that the variety of food did not affect the preference of ladybird beetle, P. dissecta. They tend to choose their natural diet, i.e., aphid in each dietary regime. We found that previous dietary regime significantly influences the mating and reproductive parameters of both the male and female except for the time to commence mating by the male. Food choices of adult beetles were found to significantly influence the time to commence mating, average fecundity and percent egg viability in males and the mating duration in females.