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- Robber flies of Germany -
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 -   Leptogastrinae

 

 

 

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  Fritz Geller-Grimm
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Identification key to the species of Leptogaster (Leptogastrinae)

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Only one genus with four species is known from Germany and the identification of these species is not easy in any case. The coloration in some characters is variable within species and therefore it is not helpful to use such features, e.g. colour of postocular bristles (occipital bristles) or antenna. This genus is a good example for the necessity of photographs for identification. There is a comparison table at the bottom of this page, which lists several characters of all included species.
L. cylindrica is very common and can be determined by the coloration of the hind legs. On the other hand L. subtilis is a rare species, which is often found in beech-forests of south-east Central Europe. The species shows a number of outstanding characteristics. I have only been able to collect two female specimens in my house until now.
The diagnosis of the hairs of the postpedicel (3rd antennal segment) made by WEINBERG & BÄCHLI (1995, S. 71) differs from my own observations. A photographic comparison table is also available.

1 a. Scutum (mesonotum) with a shiny central stripe and lateral spots [Fig. 1]; smallest distance between eyes shorter than length of pedicel (2nd antennal segment) [Fig. 2] - further characters: cf. table
. . . . . . . . . . . . Leptogaster subtilis Loew, 1847

Fig. 1: L. subtilis   Fig. 2: L. subtilis
1 b. Scutum (mesonotum) without such shiny stripe or spots [Fig. 3]; smallest distance between eyes wider than length of pedicel (2nd antennal segment) [Fig. 4]
. . . . . . . . . . . . to 2

Fig. 3: L. guttiventris   Fig. 4: L. guttiventris

2 a. Hind tibia widest at middle, width increasing up to the middle and then decreasing to tip [Fig. 5]; postpedicel tomentose basally, shiny apically [Fig. 6] - further characters: cf. table
. . . . . . . . . . . . Leptogaster pubicornis Loew, 1847

Fig. 5: L. pubicornis   Fig. 6: L. pubicornis
2 b. Hind tibia gradually widening (greatest width at tip) [Fig. 7]; postpedicel entirely tomentose [Fig. 8]
. . . . . . . . . . . . to 3

Fig. 7: L. guttiventris   Fig. 8: L. cylindrica

3 a. Hind femur with dark longitudinal stripe laterally, which is broader in apical third; hind tibia with dark longitudinal stripe laterally and apical third of tibia completely dark [Fig. 9]; tergites usually with a dark longitudinal stripe medially [Fig. 10] - further characters: cf. table

Fig. 9: L. cylindrica   Fig. 10: L. cylindrica
3 b. Hind femur with dark ring in apical third, edges of this ring blurred; hind tibia with dark area starting before middle, but apical fourth lighter [Fig. 11]; tergites more or less with transverse spots, which do not reach sides of each segment [Fig. 12] - further characters: cf. table

Fig. 11: L. guttiventris   Fig. 12: L. guttiventris

 

  L. cylindrica L. subtilis L. guttiventris L. pubicornis
Shape of postpedicel (3rd antennal segment) long-oval [photo] cylindrical and apically broken, usually yellow at base [photo] long-oval [photo] pointed-oval [photo]
Tomentum of postpedicel uniform [photo] weak [photo] uniform [photo] present at base, apically lacking [photo]
Hair on postpedicel weak [photo] dorsally distinct [photo] weak [photo] fine [photo]
Facial gibbosity at lower fascial margin distinctive [photo] lacking [photo] weak[photo] distinctive [photo]
Face beard distinctive [photo] few bristles [photo] distinctive [photo] distinctive [photo]
Distance between eyes in frontal view as wide as length of scape and pedicel [photo] smaller than length of pedicel [photo] greater than length of pedicel [photo] greater as length of scape and pedicel [photo]
Colour of palpus usually dark brownish [photo] usually pale yellow [photo] usually brownish [photo] usually brownish [photo]
Scutum (mesonotum) uniformly pale tomentose, with 3 dark longitudinal stripes [photo] usually with shiny central stripe and lateral spots [photo] uniformly pale tomentose, with 3 dark longitudinal stripes [photo] uniformly dark tomentose, with a distinct pale and narrow central stripe and paler lateral spots, which are connected with the stripe [photo]
Colour of tergites usually with dark longitudinal stripe [photo] with transverse spots, which reach the sides of each segment [photo] with transverse spots, which do not reach the sides of each segment [photo] usually sides of tergites somewhat paler [photo]
Shape of hind femur uniform, gradually expanding up to the apical fourth [photo] apical third expanded [photo] uniform, gradually expanding up to the apical fourth [photo] uniform, gradually expanding up to the apical fourth, short femora, not reaching the 2nd tergite [photo]
Shape of hind tibia gradually expanding up to tip [photo] gradually expanding up to tip [photo] gradually expanding up to tip [photo] gradually expanding up to the middle and reducing width up to tip [photo]
Colour of hind femur with dark longitudinal stripe, which is broader in apical third [photo] with dark ring in apical third, edges of which are blurred [photo] with dark ring in apical third, edges of which are blurred [photo] variable, usually dark in apical third [photo]
Colour of hind tibia with longitudinal stripe laterally and apical third completely dark [photo] apical fourth distinctly darker with clear edges [photo] darkened starting medially, but apical fourth lighter [photo] usually uniformly dark, except basally [photo]
Epandria in lateral view short, bent dorsally, pointed apically, with weak lateral points [photo 1] [photo 2] long and narrow, narrower in front of tip, inner side with distinct patch of black hairs [Foto 1] [Foto 2] short, weakly bent, with distinct lateral corners [photo 1] [photo 2] short, straight dorsally and pointed in apical third, lateral corners weak [photo 1] [photo 2]

 

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