Myrmemorpha, Dufour

Nartshuk, Emilia P. & Tschirnhaus, Michael Von, 2012, New generic synomyms in the Chloropidae (Diptera, Acalyptratae), with additional taxonomic notes, Zootaxa 3267, pp. 44-54 : 44-46

1. Myrmemorpha Dufour and Elachiptera Macquart

Dufour in 1833 described a brachypterous fly in the genus Myrmemorpha with a species brachyptera from Spain and included it within the family “athéricères” and tribe “muscides de Latreille”. The descriptions of the genus and species are rather short and are illustrated by the poor drawing of an antenna. The description of the antenna (composed from three segments) occupies three-quarters of the whole generic description. Dufour wrote that the insect looks like an ant or a small wingless ‘ichneumon’, but examination through a magnifying glass had assured him that the insect was a species of Diptera . Dufour placed the new genus not far from Mosillus in Muscidae [now in Ephydridae ].

Macquart (1835) considered the genera Myrmemorpha and Elachiptera separately, each containing a species with reduced wings, he placed Myrmemorpha after Elachiptera .

Afterwards Schiner (1862, 1864) discussed the affinity of Myrmemorpha brachyptera and concluded that Myrmemorpha brachyptera is a fly known to him as Elachiptera brevipennis Meigen and synonymized them. He assumed that Dufour had not seen the first segment of the antenna and wrongly had taken the arista as the third antennal segment. He repeated the generic synonymy in 1868 as well, using the corrected name Myrmecomorpha Dufour (an unjustified emendation created by Blanchard, 1840). Further unjustified and identical emendations were used by many later authors, mentioning the taxon wrongly also with Dufour, Agassiz or Corti as authors.

Lioy (1864: 1317–8) did not repeat the synonymy of Myrmemorpha Dufour and Elachiptera Macquart but included both separately in his family Heteromyziti, in which his subfamily Elachipterini is characterized by rudimentary wings. Lioy later (1895: 293) kept up this classification in his altered family-group taxon Elachipteri, subordered to his retained family Heteromyziti.

Bezzi (1900) in his review on the phenomenon of wing reduction in Diptera accepted the synonymy of Myrmemorpha brachyptera Dufour and Elachiptera brevipennis Meigen.

The genus and species of Dufour were listed in the Palaearctic catalogue in synonymy with Elachiptera Macquart, 1835 and E. brevipennis ( Meigen, 1830) , correspondingly ( Becker et al., 1905). This catalogue repeated the synonymy which was already published (and later repeated) by Schiner (1862: 431; 1864: 231), Neuhaus (1886: 295, 304), Gobert (1887: 43) and Bezzi (1900).

Corti (1909: 141, 145) in his revision of Elachiptera (as Crassiseta von Roser) and related genera considered Myrmemorpha Dufour, 1833 (as Myrmecomorpha— following the emendation of Scudder’s “Nomenclator”) as a valid genus and brachyptera Dufour as a synonym of brevipennis Meigen. Corti (1910) in a long and detailed discussion cited personal opinions of Enderlein and Kieffer that structures of the antenna of M. brachyptera as described by Dufour are not similar to any species of Hymenoptera. Both his correspondents tended towards the considered synonymy of Dufour’s and Meigen’s brachypterous species.

Later Becker (1909a) devoted a special paper to the affinity of Myrmemorpha and Elachiptera after Corti’s publication. His conclusion was that Schiner’s opinion on the synonymy of Elachiptera brevipennis Meigen and Myrmecomorpha brachyptera Dufour was wrong, and Dufour’s insect probably was a species of Hymenoptera. Neither Schiner nor Becker had seen Dufour’s specimen(s). Becker’s opinion does not agree with Dufour’s words “Je le pris au premier coup d’oel pour une fourmi ou un petit ichneumon aptère … la loupe vint éclaircir tous me doutes et m’apprendre qu’il appartenait à l’ordre des diptères”. Nonetheless Becker accepted the similarity of Myrmemorpha brachyptera and Elachiptera brevipennis concerning colour and size. Later Becker (1910) repeated his opinion that Myrmemorpha Dufour may not even belong to the Diptera . Enderlein (1911), Duda (1932) and Séguy (1934) placed Myrmemorpha (as Myrmecomorpha Corti ) in synonymy with Elachiptera Macquart , as Corti included in his genus only one species, E. brevipennis Meigen.

Sabrosky (1941) included Myrmemorpha Dufour in his “An annotated list of genotypes of the Chloropidae of the world …” as a doubtful genus citing the opinion of Becker (1910). Narchuk et al. (1970) listed Myrmecomorpha Corti in synonymy with Elachiptera Macquart. Andersson (1977) listed Myrmecomorpha Corti, 1909 with the species brevipennis Meigen as a synonym of Elachiptera . In the Palaearctic catalogue Nartshuk (1984) placed Myrmemorpha Dufour in doubtful names. Sabrosky (1999) placed Myrmemorpha Dufour as a questionable genus dubium in Chloropidae .

The first author failed to find Dufour’s specimen(s) in Paris in the collection of Muséum National d’Histoire Naturelle. She asked Dr J. Roháček and Dr R.H.L. Disney on their opinion if Myrmemorpha brachyptera may be a wingless species of Anthomyzidae or Phoridae and received negative answers. Species of Scenopinidae , which were mentioned by Dufour have another colour, usually black and white. By the way, Dufour distinctly wrote that Myrmemorpha belongs to “muscides” not far from the genus Mosillus , but Scenopinus to “tanystomes”. It is necessary to take in account that the genus Mosillus was included in the family Chloropidae by Schiner (1864, 1868). There exist only few European brachypterous fly species, size about 1 old French “ligne” (= 2.256 mm) and coloured like described by Dufour, firstly Elachiptera brevipennis Meigen and Stiphrosoma sabulosum (Haliday, 1837) , Anthomyzidae . The antennae of the latter species bear long distinct pubescence excluding this species from attempt at an interpretation. A further tiny brachypterous European chloropid (for example occurring abundantly on very dry SE Austrian hills, coll. von Tschirnhaus), Tricimba brachyptera (Thalhammer, 1913) and included until 1993 in the synonymous genus Crassivenula Sabrosky shows a certain colour variation: Light specimens in addition to their predominantly yellowish head and legs possess a lightened scutum with dark stripes. Also the partly swollen abdomen with its small dark or infuscated tergites within yellowish membranes appears predominantly light in such specimens. The species must be mentioned here to complete the possible range of species with a similar habitus.

The brachypterous polymorphic and tiny species of the genus Stilpon Loew, 1859 (Hybotidae) must be discussed, of which 11 species occur in Europe and two, S. graminum (Fallén, 1815) and S. lunatus (Walker, 1851) , are recorded from the mainland of Spain (Carles-Tolrá, 2002), where Briviesca (Castil), the locus typicus of M. brachyptera , is located. The reason is that their antenna nearly exactly corresponds to figure 8 on the plate accompanying Dufour’s description of Myrmemorpha . In Stilpon spp. the first article is so short and hidden that it could not have been detected by Dufour through his magnifying lens. Thus, all former discussions in the literature on the so-called three-segmented antenna including the arista were superfluous. The second article (pedicel) is nearly ball like and bigger than the third one (1st flagellomere). It surrounds cap-like the basis of the 1st flagellomere. The arista inserts only slightly above the tip (supraapical) of the flagellomere and it is directed, alife, forwards and oblique outwards and slightly downwards (in Dufour’s fig. 8 it inserts at the very tip). All these details have never been discussed in the long disputes of the authors and correspondents mentioned above. Dufour correctly figured another antenna of a typical member of the Acalyptratae, “ Sepedon ferrugineus ” ( Sciomyzidae ), which shows that he was experienced in recognizing Diptera . He says that the use of his lens dispelled all his doubts if it was a member of the order Diptera . His funny report on his insect collecting during his dangerous military service focused on the “singularité” of this antenna, he knew “no genus in the long series of Muscidae ” [translated from French] with such a configuration. A further interesting detail never was discussed: Dufour characterized the fly as “il courait avec assez d’agilité et sautillait parfois” (it ran very agil and sometimes it jumped). Just this behaviour “moving running or jumping” (“… bewegten sich laufend oder hüpfend”) was published by Joost (1991) and was also observed by the second author in a Stilpon graminum (Fallén, 1815) population feeding on Collembola on the ground of a Carex swamp in Bielefeld, Germany.

Contradicting details in Dufour’s description are [as translated]: 1) “Head plane like Oscinis planifrons ”; Musca planifrons Fabricius, 1798 was transferred to the genus Platycephala Fallén in the year 1820 and it is one of the largest European species of Chloropidae with a punctured and completely different frons than Stilpon spp. or Elachiptera brevipennis . Contrary, the frons of Stilpon spp. are narrow, slightly dusted but still shining; because the head is ovoid the frons is not outspread in a peculiar plain. 2) Length “ 1 lig[ne] ” = 2.256 mm, contrary, Stilpon spp. measure only 0.8 up to 1.6 mm, but Dufour’s measuring during military service could have been only an estimate.

Dufour’s description “Rufa, nitida, scutello abdomineque nigrescentibus; alis abdomine triplo brevioribus” corresponds well with the shining red-brown E. brevipennis and its darker hind parts (compare Fig. 9 , this article). Dufour’s figure of the antenna corresponds relatively well with a Stilpon species. Both species occur together in one habitat (caught together by the second author). Dufour said that [translated] “the tussocks were populated by myriads of small insects”. We must assume that the author mixed up both species for his description. The appropriate Latin description is here accepted for E. brevipennis , the more or less correct figure for a Stilpon species is neglected here, as well the jumping behaviour. In the nature the first author observed small jumps in E. brevipennis , too. As also Stilpon spp. are jumping we have a cast iron proof that Dufour’s observed insects could belong as well to the chloropid as to the hybotid species. These results clarify all published doubts of the past.

The puzzling last sentences of Dufour, comparing his new genus with the dissimilar genus Scenopinus Latreille, 1802 can now be intepreted better, presuming that also a Stilpon species must have been included in his material. He correctly placed one of his mixed up fly species in a group of more basic " Muscidae ", nearer to the more plesiomorphic genus Scenopinus . This genus also possesses slightly shortened wings and a rudimentary arista arising from the tip of the first flagellomere.

As the older name Myrmemorpha and its emendations had not been used (except in catalogues and lists) since 1899 in at least 25 works published by at least 10 authors in the last 50 years and encompassing a span of not less than 10 years this case is excluded by the ICZN, articles 23.9.1, 23.9.2, and 23.9.3, from involving the Commission. It is not available.

We compare the description of Myrmemorpha brachyptera with specimens of Elachiptera brevipennis and agree with Schiner that Dufour wrongly interpreted the arista as the third segment of the antenna. Therefore we consider these species as being synonyms. We add all other synonyms and their misspellings and emendations of Elachiptera , too. The six generic synonyms in Cherian (1975) are repeated opinions or errors from the literature and they are not discussed and partly not accepted here. A formal listing of Elachiptera and its synonyms is presented here:

Figures

FIGURE 9 — Elachiptera brevipennis (Meigen), alife photographed; above: 23. ix. 2007, Arnschwang (Germany, Bavaria) by Ingrid Altmann (Furth im Wald, Germany); below: 1. v. 2008, Dwarsgracht (The Netherlands) by Joke van Erkelens (Giethoorn, The Netherlands).