Mormotomyiidae

McAlpine, David, 2011, Observations on Antennal Morphology in Diptera, with Particular Reference to the Articular Surfaces between Segments 2 and 3 in the Cyclorrhapha, Records of the Australian Museum 63 (2), pp. 113-166 : 144

The Mormotomyiidae

There has been difficulty in determining the relationships of this family within the Schizophora (see Kirk-Spriggs et al., 2011, for most recent discussion). The only included species, the subapterous Mormotomyia hirsuta Austen , is only known from the type locality, Ukasi [Ukazzi] Hill, Eastern Province, Kenya, where all stages are associated with bat dung. Ashley Kirk-Spriggs has generously supplied adult males for antennal study ( Figs 178–181 , see p. 162). Hennig (1971) has described some features of the antenna.

Segment 2 is subconical in outward form; the cleft is long and deep, completely dividing the paired dorsal lobes of the rim, but their adjacent margins remain in contact ( Fig. 178 ). The distal articular surface ( Fig. 179 ) is deeply concave, extensively microtrichose, with some of the microtrichia grouped into combs, but without parallel or reticulate ridging. There is no well defined pedicellar cup, but the laterodorsal part of the surface has a deeper bowl-like concavity containing the conus, somewhat as in Leucophenga . The conus is asymmetrically developed, obsolete on the lateral side of the foramen, moderately prominent on the medial side, and well removed from the medial margin of the rim. The annular ridge is indistinct and the foramen is inclined laterally. The pedicellar button ( Fig. 180 ) is located near the dorsolateral part of the annular ridge, but is weakly developed or almost indistinguishable externally.

Segment 3 ( Fig. 181 ) has a broadly rounded, not well defined basal stem, with the basal foramen facing medially. The basal hollow is broad and of moderate depth. The sacculus is capacious, with relatively small pore near centre of lateral surface of disc. The three-segmented arista arises laterodorsally towards the base of the disc.

The deep pedicellar cleft of Mormotomyia is similar to that occurring in both the Ephydroidea and the Calyptratae. However, the asymmetrical conus, with laterally (not dorsally) inclined foramen, and the sclerotized prothoracic precoxal bridges are typical of the Ephydroidea , not of the Calyptratae. The general structure of the antenna is reminiscent of Leucophenga , a somewhat plesiomorphic example of the Drosophilidae , or could be classed between the more plesiomorphic and more apomorphic taxa of the Ephydridae ( Figs 84–93 ). The three-segmented arista, the location of the preabdominal spiracles in the pleural membrane, and, in the male, the large tergite 6 and asymmetrical sternite 6 place Mormotomyia outside the limits of the Ephydridae , but general antennal structure supports its position in the Ephydroidea suggested by Kirk- Spriggs et al. (2011).

Figures

Figures 178–181. Antenna of Mormotomyia hirsuta Austen (fam. Mormotomyiidae), male. (178) Segs 1 and 2, dorsolateral view. (179) Distal articular surface of seg. 2, seg. 3 removed. (180) Part of distal articular surface, showing button. (181) Left seg. 3, lateral view. bf, basal foramen; bh, basal hollow; bs, basal stem; bu, pedicellar button; c, conus; pc, pedicellar cleft; sc, sacculus.

Figures 84–88. Antennae of Ephydridae. (84) Ephydrella marshalli Bock, left seg. 2, seg. 3 removed, distolateral view. (85) Paralimna calva Bock, the same view. (86) Hydrellia tritici Coquillett, the same view. (87) Stratiothyrea cheesmanae Cogan & Wirth, right antenna. (88) The same, left seg. 2, distal view, seg. 3 removed. as, abraded dorsomedial surface of seg. 2; bu, pedicellar button; c, conus; cu, pedicellar cup; da, distal articular surface; pc, pedicellar cleft.

Figures 89–93. Antennae of Ephydridae. (89) Scatella sp., left seg. 3, medial view. (90) Paralimna calva Bock, the same. (91) Stratiothyrea cheesmanae Cogan & Wirth, the same. (92) Ephydrid genus E, Innaminka, S. Aust., left seg. 2, distal view, seg. 3 removed. (93) Ephydrid genus E, Lake Hindmarsh, Vic., left seg. 3, medial view. bh, basal hollow; bs, basal stem; bu, pedicellar button; c, conus; sbc, sub-basal caecum; sc, sacculus.