Aspects of the biology of Megalodontes thor Taeger, 2002 (Hymenoptera: Symphyta: Megalodontesidae).

Abstract

Some features of the biology of Megalodontes thor Taeger, 2002, a rare xerothermophilous sawfly species, are described and discussed, particularly feeding, sexual and egg-laying behaviour of imagines and habits of the larvae. At the type locality (main study area) in Southern Germany the larvae feed exclusively on Peucedanum oreoselinum (Apiaceae). At other localities further Peucedanum species are probably fed upon. Flight period at the type locality is approximately two months, which is exceptionally long for a univoltine sawfly. Copulation takes place mostly on inflorescences and mainly during dusk or dawn, whereas feeding activity takes place at higher temperatures and in full daylight. Temporal separation of these two types of behaviour has not been recorded in other Symphyta. Yellow inflorescences are strongly favoured by M. thor for feeding. Where a choice is available, inflorescences with half hidden nectaries (Ranunculus) are visited far more frequently than those with completely hidden nectaries (Asteraceae). The application of a secretion around the egg after oviposition, recorded here for the first time in the Megalodontesidae, has previously been observed in the Symphyta only in the closely related Pamphiliidae. The significance of the secretion is discussed. Differences are highlighted in the biologies of M. thor and M. cephalotes (Fabricius, 1781), the only Megalodontesidae for which comparable data are available. The highly endangered status of many Central European xerothermophilous sawflies is discussed in the light of observations on M. thor.

Keywords

Hymenoptera, Megalodontesidae, Megalodontes thor, biology, Peucedanum, Germany.