Diurnal activity patterns in hoverflies (Diptera, Syrphidae)

Abstract. 1. Time-budgets are constructed from censuses of hoverflies. Larger species spend less time in flight.
2. Most species are active under similar conditions of light intensity, but a shade-tolerant (Melanostoma scalare Fabr.) and a sun-loving species (Metasyrphus corollae Fabr.) were identified.
3. Large species become active (i.e. move, by flying or feeding) at lower temperatures than small ones, except M.scalare, which is tolerant to cool temperatures. This means that, M.scalare apart, the order of species appearing during the day is size-dependent, largest first.
4. Previous claims about the diel periodicity of syrphids can be reconciled by considering the importance of individual thermal balance.
5. Tolerance to low temperatures in small hoverflies is associated with feeding on anemophilous pollen; this may indicate a proline-fuelled flight.