Colobostema obscuritarse ( Strobl, 1898 ) Jean-Paul Haenni, 2013

Jean-Paul Haenni, 2013, A revision of the West Palaearctic species of Colobostema Enderlein, 1926 (Diptera, Scatopsidae). Part I. European subregion, Mitteilungen Der Schweizerischen Entomologischen Gesellschaft 86, pp. 199-242 : 228-231

Colobostema obscuritarse ( Strobl, 1898) comb. n.

(Figs 9A-E)

Scatopse tristis Z. var. obscuritarsis Strobl, 1898a : Mitt, naturw. Ver. Steiermark 34(1897): 277, Duda 1928: Scatopsidae, Fliegen pal. Reg. 2(1)5: 39,

Type locality. AUSTRIA, Steiermark: vicinity of Admont (Naterriegel).

Material examined. Holotype ♂ labelled: «Scat, tristis Z. v. obscuritarsis m ♀ 15/6 97 Styriae alp Strobl» [in Strobl’s handwriting until date; an additional sign in Strobl’s own sténotypie writing cannot be decyphered]; I have labelled it: « Sea - tapse tristis Z. v. obscuritarsis Strobl Holotype ♂ rev. Haenni, 1990»! « Colobostema obscuritarse (Strobl) comb. nov. Haenni 1990». Type pinned, in good condition, preserved in the NHMA, Admont.

Other material. CZECH REPUBLIC. Sumava, Horskâ Kvilda, 1130 m, 20.V-17.VI. 1999, 2 ♂♂, M. Bartâk & Kubik, CMB and MHNN; same, 21.VII—21.VIII. 1999, 1 ♂, CMB; Sumava, Rokytecka slât, 1 100 m, dates ranging from 18.V-16.VI to 21.VII-20.VI 1I.1999, 3 ♂♂, M. Bartâk & Kubik, CMB and MHNN; Podyjf NP: Braitava letohr., 520 m, 13.V-1.VI.2002, 1 ♂, M. Bartâk & Kubik, CMB ( Haenni & al. 2005).— FRANCE. Pyrénées-Orientales: Matemale (Forêt de la Matte), 21.VI. 1999, 1 ♂, P. Vacher, MHNN. Vosges: St Maurice sur Moselle (Plain du Canon), 26.V.1999, 1 ♂, T. Noblecourt, MFINN; same, 14.VI.1999,! ♂, INRAM ( Haenni & Withers 2007).- NORWAY. B0: Drammen, Underlia, V.1994, 1 ♂, L.O. Hansen, ZMB ( Haenni & Greve 2000).- SWITZERLAND. GR: Val S-charl (Plan de la Graida), 1570 m, 13.VI.1980, 1 ♂, J.-P. Haenni, MHNN; Sur, 1600 m, 3.VI.2000, 1 ♂, G. Bächli, MHNN; Dischmatal, 16-30.VI.1990, 8 ♂♂, P. Brodmann, CGB and MHNN; Marmorera, 1600 m, 2.VI.2000, 2 ♂ ♂, G. Bächli, MHNN.

Diagnosis. Males readily recognizable by shape of tergite 7 ( Fig. 9 A), with deeply emarginate posterior margin, unique among European species. The shape of the genital capsule ( Fig. 9 C) and the symmetrical, apically broadly truncate, weakly sclerotized posterior projections of the epandrium ( Fig. 9 D) are also very distinctive. The Nearctic C. arizonense Cook, 1956 shows a similar tergite 7, but clearly differs in shape of gonocoxites and epandrium.

Description. Male. 1.7 mm long; dull black in general colour, with a dense brown pilosity; notum slightly tinged, dark brown at the posterior edge of the humeral calli and a pair of small inconspicuous light spots posterior to wing base on notum; wings greyish, costal cell darker brownish, fore veins brown, hind veins greyish, somewhat darker than membrane; halters dark brown with fulvous stem; legs concolourous with body except for lighter basal third of all tibiae, apex of fore and extreme apex of middle tibiae; tarsi brownish black dorsally, brownish yellow ventral ly.

Head. Eyes largely separated on frons above antennae (about 2 ommatidia width); antennae widened towards apex, antennal flagellomeres conical, broadly separated and easy to count, wider than long from the second flagellomere.

Thorax obviously longer than wide; wing ( Fig. 9 E), 2.2 mm long, covered with dense microtrichosity; no anteriorly directed stem of vein on M,, medial fork distinctly longer than stem.

Abdomen. Pregenital segment with complete sclerotized basal ring; posterior margin of tergite 7 ( Fig. 9 A) concave, with a complex emargination; posterior margin of sternite 7 shallowly emarginate ( Fig. 9 .B); genital capsule oval, with simple, large gonocoxites ( Fig. 9 C), parameres pointed, aedeagus long, slender, epandrium with weakly sclerotized, symmetrical bilobed posterior projection ( Fig. 9 D).

Female unknown.

Taxonomic remarks. See discussion under C.flavimanum concerning the reasons for the elevation of the «variety» name of Strobl at the species level.

There is no doubt that the specimen considered here as holotype is the true type of C. obscuritarsis Strobl. It fits well with the original description and the indications of the original label also agree with it, including the date of capture. The holotype is a male, not a female, as believed by Strobl, but his confusion is easy to understand as this species has a very peculiar, strongly concave tergite 7, instead of convex as in most other congeneric species, making it superficially resemble a female. Anyway, Strobl apparently often confused the gender in this genus, since four other specimens of C. tristis in his collection, labelled as 2 ♂ ♂ and 2 ♀ ♀, are in fact 4 ♂ ♂. On the other hand, the specimen designated as type by Morge (1974.

p. 178) is clearly not the true type, although labelled «Scat, tristis Z. v. obscuritarsis m» by Strobl: the original label does not agree with the original description (date and locality differ) and, contrarily to what has been said by Morge (loc. cit.), there is no type label by Strobl himself appended to this specimen. This specimen is not conspecific with the true type, but belongs to the true C. triste (Zett.) , as well as a third specimen of the Strobl collection, also labelled “v. obscuritarsis'”. The Spanish specimens considered by Strobl (1906) as belonging to the same variety are not conspecific, according to Duda (1928), who elevated the Spanish form to species level under the name “ Scatopse strobli Duda ” (see discussion under this name).

Though not recognized by subsequent authors, C. obscuritarse Strobl is a very distinctive species, which occupies a rather isolated taxonomic place among other European species of the genus.

Distribution. C. obscuritarse has been recorded from Czech Republic ( Haenni & al. 2005), Norway ( Haenni & Greve 2000), France ( Haenni & Withers 2007) and Switzerland ( Haenni 1998). It is known from only few localities in the mountainous ranges of Central and Southern Europe, namely the Sumava range in the Czech Republic, the Alps of Austria and Switzerland, the Vosges mountains and the Pyrenees in France, and from one locality in Southern Norway. This seems to indicate a boreo-mountainous pattern of distribution. Only one known locality (Podyjf National Park, in the Czech Republic) lies at a lower elevation.

Ecology. A mountainous species in Central Europe, one Swiss specimen was swept from low herbaceous vegetation and Ericaceae scrubs in a very dry clear subalpine pine wood, in the vicinity of the Swiss National Park, at an elevation of 1570 m. All the known specimens have been collected in May or June, except some Czech specimens, trapped by a Malaise trap between end of July and end of August.

Figures

Fig, 9. Colobostema obscuritarse (Strobl): A. Tergite 7, ♂. - B. Sternite 7, ♂. - C. Genital capsule, ♂, ventral. - D. Epandrium, distal part, ♂, dorsal. - E. Wing venation, ♂.