Rohdendorfia dimorpha Smirnov, 1924:94

Genus Rohdendorfia Smirnov, 1924 comprises a small group of species confined to the Old World. The species have great similarity to species of the genera Platycheirus Le Peletier & Serville, 1828 and Melanostoma Schiner, 1860. They differ, however, in a coarsely punctured frons, scutum and scutellum, the central part of occiput is very broad, and the ocellar triangle more removed from the occiput. The profile of face is rather “nosy”, and the face widening downwards in the male. Abdomen is rather short, broad and flat, with large yellowish markings (Barkalov and Nielsen 2010).

Using the identification key of Barkalov and Nielsen (2010), R. dimorpha can be distinguished from other species by having protibia and protarsus without long pili ventrally and metafemur without long erect piliantero-ventrally. Females of R. dimorpha are very similar to females of Rohdendorfia montivaga, both with face with two longitudinal vitta of grey dusting (from frons to mouth edge), black maculae or vitta on posterior margins of abdominal terga broadened towards the lateral margins. They differ by the distribution: R. dimorpha is known from Pamir and Alaj regions.

Rohdendorfia dimorpha Smirnov, 1924.

Smirnov, E.S. (1924) Eine neue Syrphiden-Gattung aus Turkestan. Entomologische Mitteilungen 13, 94-95.

Thompson and Rotheray (1998) regard Rohdendorfia as a subgenus of Platycheirus. In the analysis by Mengual et al. (2008), Rohdendorfia species were recovered together as sister group of Spazigaster and Syrphocheilosia, refuting the subgenus status.

Synonyms:

Rohdendorfia dimorpha Smirnov, 1924: 94.

Platychirus nigripes Enderlein, 1933.

Cheilosia reinigi Lindner, 1954.

Rohdendorfia bactriana Violovitsh, 1984.

In a recent paper by Mengual et al. (2008) two representatives of Rohdendorfia were included in a molecular phylogeny of Syrphinae. This study placed Rohdendorfia as sister to Spazigaster + Syrphocheilosia, and Pyrophaena as sister to all these.

New description:

MALE.

Head: Face produced forward ventrally with a very distinct facial tubercle, shiny black with 2 lateral grey pollinose broad vita occupying all the lateral margins and narrowing ventrally towards the mouth apex, white pilose; gena shiny black with a grey pollinose area ventrad to eye, white pilose; frontal triangle black, barely grey pollinose dorsoposteriorly, black pilose; vertical triangle black, black pilose; eye bare, holoptic; antenna dark brown; occiput shiny black, withish pilose with black pili on dorsal 1/4 posterior to vertical triangle.

Thorax: Scutum and scutellum bluish black, yellowish-white pilose; postpronotum bare; subscutellar fringe incomplete with short yellow pile. Pleuron black, ywllow pilose; metasternum bare; calypter yellow; plumula white; halter capitulum yellow, stem dark; spiracular fringes yellowish. Wing: Wing membrane hyaline, slightly brown, mostly microtrichose, except 2nd costal cell bare on basal 1/6 and cell BM bare on basal 1/2. Alula broad, microtichose. Legs: Entirely dark brown, unmodified, brown pilose.

Abdomen: Parallel-sided. Dorsum mainly dark brown, darker laterally and on 1st tergum, yellow pilose; 3rd and 4th terga with 2 submedial orangish-yellow maculae that can be joined (forming a bigger macula) or separated. Sterna brown, white pilose.

FEMALE.

Similar to male except for normal sexual dimorphism and as follows: face less pollinose, laterval pollinose vitta smaller; frons black pilose. Abdomen black, with 2nd, 3rd, 4th and 5th terga black, black on posterior margin, with a medial oval orange broad fascia reaching lateral margins and anterior margins except on 2nd tergum, with a black fascia on anterior margin; orange fascia on 2nd, 3rd, 4th and 5th terga narrower on lateral margins, slightly ondulate on 2nd tergum. Sterna orange.

The Rohdendorfia species have a very unusual behavior when compared with other syrphids. Males practically do not visit flowers, and females are seen there only sometimes. The species were observed sitting on stones most of the time, or flying from one place to another. They were difficult to discover when sitting on dark stones (Barkalov and Nielsen 2010).

Rohdendorfia species are found in high alpine environs, and specimens are rather common above 2,500 m above sea level (Barkalov and Nielsen 2010).