Physocephala Schiner, 1861

Physocephala Schiner 1861: 138 [name gender: feminine]; Type-species: Physocephala rufipes (Fabricius, 1781), by original designation.

Although the genus Physocephala is one of the most distinctive amongst the Diptera, and many taxa are well known and recorded as parasitoids of various aculeate Hymenoptera, the accurate identification of the species remains very problematic. In large part this is due to the past description of many poorly defined taxa, often on the basis of colouration and dusting characters of low taxonomic value. Examination of large numbers of specimens from throughout the Palaearctic region has revealed the existence of many intermediates, suggesting that several species of Physocephala are extremely variable and that many of the described taxa are in fact synonyms. The amazing variability in size and colour of Physocephala has been described for example by Bohart (1941), Camras (1996) and Kröber (1939). A key is set out below which summarises my current understanding of the Western Palaearctic species, which should assist in their identification. It also supplements the diagnoses that are given for the species which are treated in this paper.