Thecophora


Thecophora atra, female, from Bioimages.

 

Introduction

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.

Recognition

Thecophora are greyish in general appearance. They resemble Zodion, but Zodion has but a single bent in the snout. Stuke (2006) sheds light on the former T. pusilla, showing that multiple species were hidden. T. cinerascens, T. bimaculata and T. jakutica appear in the Netherlands.

Key

1.a. Females (with a theca at the underside of the abdomen) -> 2

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

Note: The coloration of femur 3 is tricky at this point because T. bimaculata also has a pale femur 3. Stuke (2006) does not refer to the males.

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.

Literature

Stuke J.-H. 2006. Thecophora pusilla auct. - ein Artenkomplex. Beitr. Ent. 56(2): 269 - 279.

Van Veen M. 1984. De Blaaskopvliegen en roofvliegen van Nederland en België. Jeugdbondsuitgeverij, Utrecht.

Last updated 8.2.2004