Thecophora

1.b. Males (approximate key, characters variable!) -> 10

2.a. Theca not projecting, normally laying flat on the sternites, if partly erected, the hind rim of the theca strongly bent near the basis -> 3

2.b. Theca projecting, perpendicular on the sternites, hind rim not bent -> 5

Abdomen and theca of female of, first, Th. melanopa, with theca laying flat against the sternites and, second, Th. atra, with theca erect.

3.a. Snout: 2nd and 3rd piece each about as long as the height of the head, at most 10-20% longer; femora: black to yellow on basal half -> 4

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.a. Femur 3 black. 4-6 mm. -> Thecophora melanopa Rondani

4.b. Femur 3 on its basal half yellowish. 5-7 mm. -> Thecophora distincta Wiedemann in Meigen

5.a. Theca in hind view as long as wide, rounded. 4-5 mm. -> 6

5.b. Theca in hind view elongated, lateral margins converging from base to tip -> 9

Abdomen and theca of females of, first, th. cinerascens, with theca rounded and, second, of Th. atra, with theca elongate.

6.a. Femur 1 and 2: black, femur 3 only pale on basal half -> 7

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.a. Theca in hind view: bristle field occupying half or less of the theca length at the median part, with 4 or less rows of bristles; head: ocellar triangle tawny or black -> 8

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

10.a. Thoracic dorsum with two black undusted lines in a large field of grey dust -> 11

10.b. Thoracic dorsum with two grey lines of dust leaving a single undusted, black line in between, on the remainder of the thoracic dorsum hardly any dusting -> 13

11.a. Femur 3 black. 4-6 mm. -> Thecophora melanopa Rondani

11.b. Femur 3 partly yellow -> 12

12.a. Snout: 2nd and 3rd piece each about as long as the height of the head, at most 10-20% longer; femora: yellow on basal half. 5-7 mm. -> Thecophora distincta Wiedemann in Meigen

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.a. Femur 3 at most yellowish on its basal half, femur 1 and 2 black to brown, hardly paler on inside -> 14

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.a. 2nd antennal segment longer than the 3rd segment; femur 3 yellowish on its basal half. 5-7 mm. -> Thecophora atra Fabricius

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.