Austrosimulium dumbletoni Crosby, 1976

Craig, Douglas A. & Crosby, Trevor K., 2008, Gynandromorphs of New Zealand Austrosimulium spp. (Diptera: Simuliidae), Zootaxa 1811 (1), pp. 57-68 : 60-61

Austrosimulium dumbletoni Crosby, 1976 .

Of the eight specimens, only one (#3) has both fully expressed male eyes with large ommatidia, but they are dichoptic, a female characteristic. One (#2) possesses a partially developed male eye on the left. One (#4) is essentially fully male on the left side of the head. Four (#1, 5, 6, 7) have complete female heads. Four (#2, 3, 6, 7) have antennae that are both female; the remaining specimens have male and female antennae. All specimens have fully developed female mouthparts, by which we mean substantial labrum and labium, and well developed mandibles and lacinae (e.g. Fig. 8). However, that mandible has teeth on the aboral surface at the apex – a condition not associated with Austrosimulium females. Two (#3, 4), however, have male maxillary palpi (Fig. 8). Two (#1, 6) have only one male maxillary palpus, the other female. Five (#2-6) have a fully domed male thorax, while two (#1, 7) are mainly female (Fig. 1). One specimen each possesses only male claws (#2) or only female claws (#7—see below) on the legs, the remaining six have mixtures of either male or female claws on each leg (e.g., Figs. 2, 3). Three specimens (#4, 6, 8) have fully expressed male genitalia with little if any indication of abnormality. One (#2), while with fully male genitalia, has slight indication of female structures (genital fork?) anteriorly to that. One (#1) (Fig. 1), while with fully male genitalia, possessed a female-like 8th sternite and a spermatheca (Fig. 6). Two (#5, 7) are fully female with minor abnormalities to the genitalia. Specimen #7 may not be a gynandromorph, since it merely has some minor asymmetry of its female genitalia.

Of the most interest is Specimen #1, that at first appears to be a blood-fed female and possesses a fully developed female head with a complete set of apparently functional mouthparts, but with full male genitalia (Fig. 1). Its combination of features is noted above. Further to this though, its legs are of mixed provenance with the forelegs both female (Fig. 2), and the mid legs female on the right and male on the left side. Both hind legs are male (Fig. 3). Male claws in Simuliidae have a grappling comb on the dorsal surface for engaging the female vestiture during copulation ( Craig and Craig 1986). The abdomen is a mosaic of both male and female parts, and the tergites (e.g., Fig. 9) span the full width of the segment as is normal for Austrosimulium (Dumbleton 1972) males. Each tergite, however, has portions with female vestiture. The first abdominal segment, or basal scale, possesses long black hairs, typical of simuliid males (Crosskey 1991) on the right side, as in Figure 9. The male genitalia are unremarkable, except for a minor amount of asymmetry to the ring-like ninth sternite (Fig. 6). Initial examination indicated a certain amount of malformation (Figs. 1) of the 8th sternite immediately anterior to the gonocoxites.

The swollen anterior portion of the abdomen was not full of bird blood as had been initially surmised, but rather by a large number (200–300+) of fully developed chorionated eggs (Fig. 4), plus an equally large number of small pre-vitellogenic oocytes (Heming pers com. 2008). Further, the insect has a well-developed sclerotized spermatheca (Fig. 6) of unremarkable form, but apparently lacking a duct. The deformed 8th sternite now could be interpreted more probably as part of the female genital fork. What appeared to be three openings, one encompassed by the genital fork and the other two immediately posterior of that are, at high magnification, not openings. This is in agreement with lack of a spermathecal duct.