Thecophora are small greyish Conopid
flies, that dwell in the vegetation. They are not often observed in the
field. Most flies are spotted in open grasslands in forested
environments, while visiting flowers. Flower visits include yellow
composites as Crepis biennis.
Abdomen and theca of female of, first, Th. melanopa, with theca laying flat against the sternites and, second, Th. atra, with theca erect.
3.b. Snout: 2nd and 3rd piece each twice as long as the heigth of the head; femora completely yellow to yellow on basal half. B. -> Thecophora longirostris Lyneborg
4.b. Femur 3 on its basal half yellowish. 5-7 mm. -> Thecophora distincta Wiedemann in Meigen
Abdomen and theca of females of, first, th. cinerascens, with theca rounded and, second, of Th. atra, with theca elongate.
6.b. Femur 1 and 2: at least pale on basal half, femur 1 often completely pale on inner side, femur 3 pale on at least basal half; wing base with extensive yellow coloration: radius yellow well after the branching of veins R1 and R2+3; abdomen: tergite 6 obviously dusted medially. Southern and central Europe. -> Thecophora bimaculata (Preyssler)
7.b. Theca in hind view: bristle field broad, more than half the theca length at the median part, with 5 rows of bristles; head: ocellar triangle yellow or orange-brown, without an obviously defined black area at rear. Eastern palaearctic. -> Thecophora apivora Zimina
8.a. Theca from behind: bristle field almost reaches the base of the theca at the side; head: frons and ocellar triangle uniformly tawny. Central and southern Europe, Eastern palaearctic. -> Thecophora jakutica Zimina
8.b. Theca from behind: bristle field reaches only halfway the theca at the side; lower part of frons pale, upper part and ocellar triangle uniformly black; wing base: radius only yellowed until just before the branching of veins R1 and R2+3, then black beyond; abdomen: tergite 6 usually not or only negligibly dusted medially. Southern and central Europe -> Thecophora cinerascens (Meigen)(= Thecophora pusilla)
9.a. Thorax and abdomen with golden dust; femur 3 yellowish on its basal twothirds, femur 1 and 2 brownish, turning yellowish at their inner side; thoracic dorsum with two well marked lines of grey dust, with a clear undusted black line between them. 7-8 mm. -> Thecophora fulvipes Robineau-Desvoidy
9.b. Thorax and abdomen with grey dust; femur 3 yellowish on its basal half, femur 1 and 2 brown to black, not turning yellow at their innerside (at most black parts turning brown); thoracic dorsum with two badly marked grey lines of dust, not leaving a sharp black line between them. 5-7 mm. -> Thecophora atra Fabricius
12.b. Snout: 2nd and 3rd piece each twice as long as the heigth of the head; femora completely yellow to yellow on basal half. B. -> Thecophora longirostris Lyneborg
13.b. Femur 3 yellowish on its basal twothirds, femur 1 and 2 brownish, turning yellowish in their inside. 7-8 mm. -> Thecophora fulvipes Robineau-Desvoidy
14.b. 2nd antennal segment as long as or shorter than the 3rd segment; femur 3 often only yellowish on its basal quarter. 4-5 mm. -> Thecophora cinerascens (Meigen) (=Th. pusilla) and Thecophora bimaculata, two further species in the eastern palaearctic.
Van Veen M. 1984. De Blaaskopvliegen en roofvliegen van Nederland en België. Jeugdbondsuitgeverij, Utrecht.