Ephydridae, Zetterstedt, 1837

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 : 141-143

The Ephydridae

For this study I examined the antennae of the following species: Ochthera pilimana Becker , Scatella sp. , Ephydrella marshalli Bock , Paralimna calva Bock , Hydrellia tritici Coquillett , Stratiothyrea cheesmanae Cogan , Risa longirostis Becker , “ephydrid genus E”, which includes several Australian species living in saline habitats. I previously examined the arista of numerous ephydrid taxa (D. McAlpine, 2002), and found it to be usually two-segmented through loss of segment 4, but in a few cases it is even further reduced. Wirth et al. (1987: particularly figs 41–44) show some of the variation in antennal form in the family.

Antennal structure in the family Ephydridae shows most of the range of variation occurring in the superfamily Ephydroidea ( Figs 84–93 ). In Scatella and Ephydrella the conus arises from the medial side of the distal articular surface and is seen to project markedly beyond it in medial view; a ridge extends from the ventral base of the conus across the articular surface, defining a shallow cup-like depression which occupies the dorsolateral part of the surface. The annular ridge and foramen are asymmetrical and face laterally. Segment 3 has a shallow basal hollow, deepening to a central pit. The basal foramen is located in a concavity on a broadly rounded prominence on the margin of the hollow, which could be regarded as an incipient basal stem. The pore of the sacculus is located laterally, far from the ventral margin. In segment 2 of Ochthera the conus is somewhat similar but there is no transverse ridge extending from its base. Segment 3 has a distinct but short basal stem. Hydrellia and Paralimna have a more reduced conus, and, although the distal articular surface is markedly and narrowly deeper dorsolaterally, there is no defined cup. Segment 3 has a definite basal stem which is not strongly narrowed, though tapering to a point in Paralimna . In Stratiothyrea the distal articular surface of segment 2 is almost flat on much of its extent, with narrow dorsal cleft and very deep abrupt subcentral cup quite unlike any of the above examples. The conus is almost absent and the annular ridge is located only slightly asymmetrically on the floor of the cup. Segment 3 is markedly differentiated into the narrow, digitiform basal stem and broad disc; the rather narrow sub-basal caecum opens on to the medial surface of the stem a little distance from the disc; there is a slight indication of a separate basal hollow on the medial side of the broad basal surface of the disc. The antennal structure of Stratiothyrea is remarkable for its resemblance to that of such advanced drosophilids as Tambourella , evidently through detailed convergence. Like these two genera, Camilla acutipennis (Loew) (family Camillidae ) also has an elongate basal stem ( Hennig, 1971: fig. 8).

In “ephydrid genus E” segment 2 ( Fig. 92 ) is more elongate than that of many ephydrids, with the lobe on the medial side of the dorsal seam more prominent than that on the lateral side; the distal articular surface is less deeply concave than that of most ephydrids and without any suggestion of a cup-like cavity; the conus is relatively narrow, but strongly projecting and arising close to the medial dorsal lobe; the foramen faces entirely laterally. Segment 3 ( Fig. 93 ) has no basal stem; the basal foramen is on a slight scabrous prominence on the lateral margin of the basal hollow; the hollow is capacious, tilted medially, and its floor has a narrow caecum-like extension; the pore of the sacculus is in a ventral position, as in Risa , but in contrast to other examined ephydrids, which have it in a lateral position. The arista lacks segment 4; segment 6 is numerously and irregularly pubescent on c. the basal 0.4 of its length, but beyond this has only a dorsal series of c. 10 very short rays. The arista is thus fairly typical of the Ephydridae , while some other features, including the ventral position of the sacculus, the elongate prementum of the proboscis, the characteristic facial contour, the prominent vibrissa, the milky-white wing membrane, the rather long unpigmented but slightly sclerotized crease representing vein 6, and the almost complete suture separating abdominal tergites 1 and 2, suggest placement in the subfamily Risinae , which was formerly given separate family status.

Figures

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.