Biology session

Efficient foraging is a necessity for living organisms' survival and reproduction, often competing for food resources against their conspecifics and other species. This competition has led to extremely diverse ways of foraging. For instance, nectar feeding insects have to detect nectar sources and assess their actual value compared to other potential sources. The majority of butterflies feed on nectar as imago. The choice of nectar sources is determined by the individuals' learning abilities, flight time, proboscis length, body mass, wing load, energy requirements, flower size, colour, pattern and scent, quality and quantity of the nectar.

My aim is to analyse foraging efficiency in Clouded Apollos on different nectar sources. Males search for females by patrol flight and may produce sphragis during mating. Females lay eggs and fly between the feeding and ovipositioning locations. Probably to cover the cost of these activities, both sexes spend a lot of time on foraging.

Clouded Apollos feed on ca. the half of the insect pollinated flowering plants available in their habitat, but they visit frequently only a few species and these few can change among years. The choice is probably determined by the relative frequency of the nectar sources and the amount of nectar. Proboscis length, highly variable in the population, may limit access to at least one important nectar plant. However, the effect of species-specific inflorescence structures on feeding efficiency is still unknown. In this study, I present data on feeding efficiency on the most frequented five nectar resources of the Clouded Apollos by analysing videos.

We carried out field work in the Visegrádi-hegység and Börzsöny, 2010 – 2016. I measured (i) the time proportion the proboscis was inserted in the corolla during the time spent on flowers, inflorescences and between the flowers, (ii) how and how many times the butterflies changed flowers or inflorescences, and I estimated profitability for each nectar sources.

The profitability of four sources was similar, one of them was less profitable. Females spent more time than males foraging on a single flower and they switched less often. This may be explained by the different metabolic rates of the sexes. In case of one resource species, butterflies spent more time changing to a nearby inflorescence than in other species. This can be energetically more costly than changing between flowers in one inflorescence, because they often have to fly when switching flowers.