Pachychoeta Bezzi

Nartshuk, Emilia P. & Tschirnhaus, Michael Von, 2012, New generic synomyms in the Chloropidae (Diptera, Acalyptratae), with additional taxonomic notes, Zootaxa 3267, pp. 44-54 : 48

3. Pachychoeta Bezzi , Pachychaetina Hendel , Melanochaeta Bezzi and Oscinella Becker.

The species Oscinis capreolus , described by Haliday (1838: 187) from England was subsequently listed within the generic names Siphonella Macquart ( Becker et al., 1905: 176) , Elachiptera Macquart ( Becker, 1910, Duda, 1932), Pachychoeta Bezzi, 1895: 34 (as aterrima Strobl ), Pachychaetina Hendel, 1907: 98 (as aterrima Strobl ), and Melanochaeta Bezzi, 1906: 50 (as aterrima Strobl ) ( Nartshuk, 1984: 232; Sabrosky, 1965, 1971). The species is the senior synonym of aterrima Strobl, 1880: 34 , described in the genus Elachiptera Macquart and also of coei Nartshuk, 1965: 18 , decribed in the genus Oscinella Becker.

In 1880 Strobl described Elachiptera aterrima Strobl from Austria. Bezzi (1895) erected a genus Pachychoeta with the type species Elachiptera aterrima Strobl. The name Pachychoeta was preoccupied by Bigot, 1857, and Bezzi (1906) proposed a new name Melanochaeta with the same type-species. Then Hendel (1907) proposed a further name, Pachychaetina with the same type-species. Corti (1909) and Becker (1910) listed this species in the genus Melanochaeta Bezzi.

In 1898 Thalhammer described Elachiptera pubescens from Hungary, Dalmatia and Hercegovina. His species pubescens was listed together with aterrima in the genus Pachycheta (sic!) in the Catalogue of Palaearctic Diptera ( Becker et al., 1905) .

Corti (1909) noted similarity of M. aterrima with species of the genus Oscinella Becker , especially O. albiseta (Meigen) and O. maura (Fallén) , he considered both latter as valid species. He erected a new genus Lasiochaeta for pubescens Thalhammer , as this species has a reniform first flagellomere and a scutellum without warts (but see discussion below). Later Corti (1910) discussed similarity of the species maura (Fallén) and aterrima Strobl , especially on their structure of the male genitalia and he illustrated male genitalia, unfortunately too small. Collin (1946: 147) also wrote that “ M. capreolus Hal. , except for its arista, might easily pass as a species of Oscinella ”.

Now we formally transfer capreolus to the genu s Oscinella Becker though it was already done with its junior synonym M. coei by Nartshuk (1984). The transfer is based on the structure of the male genitalia but further characters of capreolus do not prevent to include the species in the genus Oscinella : black body, round first flagellomere, shining large ocellar triangle, short and not produced palpi, shining pleura, short semicircular scutellum. The structure of the flattened and densely pubescent arista is not in conflict with characters of the genus Oscinella as O. maura (Fallén) has a thick pubescent but not flattened arista which is not black but white. Evolutionary clines of flattening the arista have been studied by Andersson (1979). In the genus Lasiochaeta the body is grey because densely dusted, the first flagellomere is reniform, the palpi are distinctly protruding from the oral cavity, the scutellum is trapezoidal with apical setae arising apart. O. capreolus has male genitalia of the Oscinella type with rather big and nearly triangular cerci and simple gonites not widened in apical part ( Figs 1–4). The species pubescens Thalhammer has a different structure of male genitalia with smaller cerci and gonites widened in apical part, similar to species of the genus Elachiptera Macquart ( Figs 5 –8).

Figures

FIGURES 5 & 6 — Male genitalia of Elachiptera brevipennis (Meigen): 5 — epandrium, 6 — hypandrium and phallic organs. FIGURES 7 & 8 — Male genitalia of Lasiochaeta pubescens (Thalhammer): 7 — epandrium, 8 — hypandrium and phallic organs.