Zalea dayi, McAlpine, 2007

McAlpine, D. K., 2007, The Surge Flies (Diptera: Canacidae: Zaleinae) of Australasia and Notes on Tethinid-Canacid Morphology and Relationships, Records of the Australian Museum 59 (1), pp. 27-64 : 59-60

Zalea dayi n.sp.

Figs 13, 38, 77, 85, 86

Material examined. HOLOTYPE!, New South Wales: Seal Rocks (headland, north side), 11.x.2000, D.K.M. ( AM). Dry-mounted on triangular point . PARATYPES. New South Wales: 4??, 4!!, Black Head (Haliday’s Point), Taree district , 13.ix.2000, B.J. D. ( AM, USNM) ; 11??, 7!!, “The Ruins”, Booti Booti National Park, Forster district , 15.ix.2000, B.J. D. ( AM, ANIC) ; 35??, 30!!, Seal Rocks , 26.ix.2000, 9–11.x.2000, D.J.B., D.K.M. ( AM, ANIC, BM, BPB, CNC, TAU, USNM). Material from Black Head and “The Ruins” in alcohol; that from Seal Rocks mostly drymounted on points or micro-pins with abdomens extended .

Other material. New South Wales: 1!, Vaucluse, Sydney Harbour , 25.i.1964, D.K.M. [ AM, originally determined as a paratype of Z. minor (D. McAlpine) ] .

Description (?,!). Very small dull, dark greyish fly, with unmarked wing, with general characters as for genus Zalea .

Coloration. Head predominantly brown, with brown to grey pruinescence; anterior part of postfrons yellowish brown; parafacial and upper part of cheek pale yellow to greyish yellow. Antenna yellow; segment 3 often with slight tawny suffusion; arista dark brown. Prelabrum grey; palpus yellow. Thorax with brown-black ground colour, densely covered with grey to brown pruinescence; bristles black. Legs dark grey-brown. Wing membrane uniformly smoky grey; veins brownish. Halter yellow basally, with creamy capitellum. Abdomen dark grey-brown, almost entirely pruinescent; in male, anterior surstylus generally (at least in fresh material) dark brown, often more yellowish apically; in female, paired sclerites representing tergite 7 and sternite 7 shining black, each with short grey-pruinescent zone at posterior end; cercus of female brown, becoming black apically.

Head. Proportions resembling those of Z. major (D. McAlpine, 1982: figs 1–3); height of cheek c. 0.26–0.28 of height of eye; postvertical bristles slightly to strongly divergent.Antenna similar to that of Z. minor in proportions; arista c. 1.3–1.6 times as long as rest of antenna. Palpus only slightly thickened distally, where it is not more the c. 0.5 times as deep as cheek and at most very slightly deeper than prelabrum (i.e. very similar to palpus of Z. minor ).

Thorax. Prosternum without precoxal bridge; chaetotaxy and most leg characters as for genus. Tibiae without any such enlarged dorsal or posterodorsal setulae or bristles as occur in Z. clava and Z. johnsi . Wing venation very similar to that of Z. minor , the little variation in contours and proportions apparently allowing no constant differences; cell-4 index = 0.55–0.61.

Abdomen. Sternite 1 deeply emarginate on posterior margin, almost divided in two; a pair of small sclerites between sternite 1 and sternite 2 (these form part of segment 2 in Z. minor and Z. major ); other preabdominal sternites broader than in Z. minor . Male: anterior surstylus much broader than that of Z. minor , neither broadened basally nor significantly tapered distally; posterior surstylus finely pointed at apex, with some long setulae, but these relatively sparse, without anterior gibbosity. Female: sternites 2 to 5 all broader than long; sternite 6 large, undivided; tergite 6 as long as tergite 5, with median desclerotization on posterior margin less extensive than in Z. major , and posterolateral angle not produced as in that species; paired sclerites of sternite 7 very narrow, separated by more than 4× width of each; paired sclerites of tergite 7 ( Fig. 77) relatively large, each more than twice as long as wide, separated by well defined membranous median zone.

Dimensions (dried, some with abdomen artificially extended, parts behind tergite 6 excluded in!). Total length,? 1.7–2.1 mm,! 1.9–2.3 mm; length of thorax,? 0.72–0.86 mm,! 0.75–0.99 mm; length of wing,? 1.8–2.0 mm,! 2.0– 2.4 mm; width of epandrium 0.26–0.29 mm.

Distribution. New South Wales: sea coast from Taree district to Sydney Harbour, between c. 32°00'S and 34°02'S. Zalea dayi may prove to have a wider distribution, especially as old dried specimens can be difficult to distinguish from Z. minor . However, recently made collections of Zalea from more northern localities in New South Wales and from eastern Tasmania include no Z. dayi .

Notes

Zalea dayi , though similar in size and superficial features to Z. minor , is sharply differentiated from all other Australian Zalea species in abdominal characters. In the male, the broad, almost parallel-sided dull brown anterior surstylus and apically pointed posterior surstylus are distinctive. In the female, the very narrow, widely separated paired sclerites of sternite 7, and the large, but elongate, largely shining black, well separated sclerites of tergite 7 are also distinctive; the much broader abdominal sternites 2 to 6 differentiate it from the sympatric Z. minor and Z. major .

The specific epithet refers to Barry J. Day, from whose material I first recognized the distinction of this species.