Diurnal activity patterns of Platycheirus hoverflies (Diptera: Syrphidae)

Hoverflies are important plant pollinators which frequently visit flowers of many kinds of plant species. Although some aspects of the Syrphidae are well studied, the environmental conditions, foraging behaviours and activity rhythms of species within genera need further study in an evolutionary context. We considered the temporal activity rhythms of Platycheirus species to environmental factors such as ambient temperature and Relative Humidity (RH). Platycheirus activity depended mainly on temperature, and the individual species responded differently: the optimum temperature for achieving activity was between 13–23°C. The proportion of active individuals increased as the morning progressed, peaking before noon, indicating a unimodal activity pattern. Flight behaviour correlated negatively with temperature. Most observations fell between 50% − 80% RH. Males and females were similar in handling times on flowers, taking nectar and pollen, as well as the kinds of flower used. Handling times in the morning were longer than in the afternoon. Foraging speed not constrained phylogenetically (i.e species spent different times for foraging). Understanding behavioural responses to microclimate is a necessary component of insect adaptations to their environment.