Helosciomyzidae

McAlpine, David K., 2012, Notes and Descriptions of Australian Helosciomyzidae or Comb-winged flies (Diptera: Schizophora), Records of the Australian Museum 64 (1), pp. 51-70 : 54-56

Taxonomy of Helosciomyzidae

The Helosciomyzidae are probably most closely related to the Dryomyzidae , which are restricted to the Northern Hemisphere, or perhaps to the Helcomyzidae , represented in both hemispheres but not in Australia (see Meier and Wiegmann, 2002 for probable phylogenetic relationships). The Helosciomyzidae can be separated from these related families by the following combination of characters.

1 Costa of wing with a series of large spaced spines near and beyond termination of subcosta ( Fig. 5 ).

2 Costagial bristles two, anteroventral one located distad of anterodorsal one ( Fig. 4 ).

3 Anal cell (cell cup) less than half as long as second section of vein 4 (between basal and anterior crossveins).

4 Anal crossvein (transverse section of CuA2) very strongly recurved.

5 Distal section of vein 6 (CuA2+A1) thickened

on c. basal third or less, then becoming rather abruptly attenuated, but visibly reaching wing margin.

6 Prosternum without precoxal bridges.

7 Metasternum without setulae.

8 Three postgenal bristles generally differentiated

( Fig. 13 ), except in occasional deviant individuals.

9 Tarsi with distal segments depressed.

10 Preabdominal spiracles located in pleural

membrane.

11 In males, fore and hind basitarsi without rounded terminal ventral projection.

12 In females, abdominal tergites 3 to 5 without

single enlarged lateral marginal bristle, with largest bristles on posterior margin.

13 In females, abdominal tergite 7 and sternite 7 separated by pleural membrane.

Most helosciomyzids have a distinct membranous line in the mid-dorsal region partly separating abdominal tergites 1 and 2, and Barnes (1981: table 1) has given this character as a distinction between “ Helosciomyzidae sensu stricto” and “ Dryomyzidae sensu stricto”, which have this suture indistinct. However, in the helosciomyzid genus Polytocus Lamb there is no trace of such a suture, and in Sciogriphoneura Malloch it is reduced to a slight groove without desclerotization. The character is therefore omitted from the above list.

The Neotropical genus Sciogriphoneura Malloch was placed in the Dryomyzidae by Steyskal (1977) and in the Helosciomyzidae by Barnes (1981). My study of S. nigriventris Malloch , shows it to agree with the Helosciomyzidae in the first twelve of the numbered character states given above, except that one specimen shows asymmetrical variation in the number of postgenal bristles (character 8). In the only available female segment 7 is not visible, so that character 13 cannot be assessed. On the other hand, typical dryomyzids show disagreement in characters 1, 2, 3, 4, 5, 8, 9, 10, 11 (the last character inconsistently); but this assessment does not include the genus Oedoparena Curran , which I regard as doubtfully referable to Dryomyzidae . [The larvae of Dryomyza Fallén (objective syn. Neuroctena Rondani ) and Oedoparena (see Ozerov, 1998, or, for more detail, Burger et al., 1980, and Barnes, 1984) are so different in external form and structure that discovery of a strong set of synapomorphies is required to justify the inclusion of both taxa in one family]. Barnes (1981: 64) recorded that Sciogriphoneura possesses, in the male, both the anterior epandrial process and the basal surstylar process, as in many more plesiomorphic helosciomyzids, but the former is also present in typical dryomyzids.

On the above basis I confidently assign Sciogriphoneura to the Helosciomyzidae . I believe that this correction, together with others made previously (D. McAlpine, 1995), leaves no valid record of the Dryomyzidae in the Southern Hemisphere.

Griffiths (1972) included the endemic New Zealand group, now called Huttoninidae , in the Helosciomyzidae , but Barnes (1979, 1981) considered that there were no clear synapomorphies to justify combining the two groups. Colless and McAlpine (1991) recognized the Huttoninidae as a separate family. The Huttoninidae are distinguished from the Helosciomyzidae by having: no spaced costal spines; distal section of vein 6 strongly sclerotized, but terminating abruptly at c. three quarters of distance to wing margin; vein 7 not forming a visible crease beyond alula; abdomen of female with tergite 7 and sternite 7 fused. Barnes (1979) also stated that the huttoninids differ in having the aedeagus bilobed, covered with fine scale-like structures. I am not at present in a position to test the consistency of this condition. The huttoninids generally have the ptilinal fissure less developed than in the helosciomyzids, though variable in extent and perhaps not always functional. In the Helosciomyzidae the ptilinal fissure apparently encloses a functional ptilinum, and its lateral arms are moderately long, usually ventrally diverging from the parafacial suture (terminating close to parafacial suture in Scoiogriphoneura). The Helosciomyzidae , in common with the Dryomyzidae , Helcomyzidae , Coelopidae , and Heterocheilidae , have the postalar callus of the mesoscutum convex, defined by an oblique depression or shallow groove on the anteromedian side, and bearing two large bristles ( Fig. 11 ). In the Huttoninidae , as in the Lauxaniidae , the postalar callus has no separate convexity, and no oblique depression separates it from the general dorsal surface of the mesoscutum ( Fig. 12 ); it bears a typical postalar bristle on its lateral angular prominence and the second, more dorsal bristle occupies the position of a typical posterior intra-alar bristle.

From Australasian taxa of Sciomyzidae , the Helosciomyzidae can generally be distinguished by having the prelabrum (“clypeus” in error) anteriorly prominent and only narrowly separated from the face (more reduced in the New Zealand genera Napaeosciomyza Barnes and Dasysciomyza Barnes ), the costa with prominent spaced spines, and usually two large sternopleural bristles (anterior one sometimes reduced in very hirsute males). I have noted previously (D. McAlpine, 1991b) differences between the Helosciomyzidae and Heterocheilidae .

The Helosciomyzidae , in contrast to the Dryomyzidae , are restricted to the Southern Hemisphere. The majority of the 27 or 28 known species live in the temperate zone, but in both Australia and South America one species is recorded for the tropics. Of the 15 known Australian species, only two widely distributed species are recorded for Queensland, whereas at least eight species live in Tasmania, four of them possibly endemic to the state. Eleven species are recorded for New Zealand ( Barnes, 1981), but it is uncertain if one of these is the same as an Australian species.

Figures

Figure 13. Eurotocus australis, head of female. Three postgenal bristles indicated.

Figures 4, 5. Luta luteipennis, left wing. (4) anterior view of basal section. (5) anterior view of part of costa near end of subcosta. bc, basicosta; cb, costagial bristles; cg, costagium; h, hairs; mi, microtrichia; sl, spinules; sp, spine; tg, tegula.

Figures 11, 12. (11) Luta luteipennis, part of thorax showing right postalar callus. (12) Huttonina abrupta Tonnoir & Malloch, part of thorax showing right postalar region. Postalar bristle indicated.