Froggattimyia wentworthi, Malloch, 1934

Colless, Donald H., 2012, The Froggattimyia-Anagonia Genus Group (Diptera: Tachinidae), Records of the Australian Museum 64 (3), pp. 167-211 : 174-176

Froggattimyia wentworthi Malloch

Figs 1, 2, 5–7

Froggattimyia wentworthi Malloch, 1934:3–4.

Type. Holotype male in ANIC, Wentworth Falls, NSW.

Male. Head (Figs 1, 2): Width 3.6–4.4, mean 4.02 mm., approximately 4 times as wide as frons; Gnw/Eyh 0.5–0.6, mean 0.53; Ivb/Vb-E = 0.7–0.9, mean 0.8. Ground colour

pale brown anteriorly and ventrally, dark brown to black on occiput and dorsally on fronto-orbital plate. Anterior surfaces with golden to pale golden pollinosity, except for thinner, silver pollen on face; silvery to very pale golden pollen on postorbits dorsally and silver-grey on occiput. Scape pale brown with a row of minute setulae; pedicel pale brown with pale grey pollen in appropriate light and usual cluster of short spines and setulae; first flagellomere pale brown basally, darkened to a varying degree along dorsal (anterior) margin and across apex; aristomere 3 pale brown on most of the swollen basal portion. Mouthparts pale brown. Inner vertical bristles well developed, slightly inclinate in facial view, somewhat reclinate in lateral view; outer vertical bristles at most finely or (usually) not at all differentiated; ocellar seta fine, sometimes lacking, but usually clearly differentiated; postocellar setae 2–6 (usually more than 2). Reclinate upper orbital bristles not clearly differentiated from adjacent bristles along narrowed part of interfrons, between eyes and immediately in front of ocellar triangle, but 1 or more pairs of reclinate upper orbital bristles sometimes differentiated, standing in line with upper frontal bristles. Vertex, frons, and parafacial with black hairs and setulae. Parafacial setulose to at least centre and usually with at least a few scattered setulae on ventral half; sometimes almost completely setulose and/or with a detached cluster of tiny setulae at ventrolateral angle, near eye. Genae with at least a few (usually mainly) dark setulae on anterior, convex portion, becoming orange-brown on ventral areas. Gular, postgular, and occipital areas with pale brown to orange hairs and setulae. Postocular strip with 1–2 rows of dark hairs.

Thorax. Dorsally, ground colour mainly black, with silvergrey dusting except on 2 pairs of narrow vittae, interrupted at the suture, one between dorsocentral and acrostichal rows of bristles, reaching to about the level of second postsutural dorsocentral, the other between dorsocentral and intra-alar rows, reaching almost to scutellum; sometimes a short median postsutural vitta as well. However, ventral half of anterior pronotum with pale dusting, and postalar callus with brown ground colour. Bristles and setulae dark, except for pale brown hairs on ventral half of pronotum and sometimes at sides of scutellum. Postpronotal bristles 3–4 in a row; presutural dorsocentral bristles 3 (rarely 2 or 4) + 4 postsutural bristles (rarely 5); acrostichal bristles 3 + 3 (rarely 4); intra-alar bristles typically with 1 presutural (usually rather fine, occasionally out of line or missing) and 3 postsuturals, the first occasionally missing; also, 2–3 posthumeral bristles, a stout presutural, and 2 (rarely 3) notopleural bristles; first postsutural supra-alar (prealar) seta rather larger than first postsutural intra-alar but smaller than first postsutural dorsocentral. Intrapostalar bristle well developed, about as large as first postsutural dorsocentral. Scutellum with dull brown to dark brown ground colour, and grey dusting visible at a viewing angle of about 45°; the usual basal, lateral, discal (1 or 2), and subapical pairs of bristles present, the latter strongly divergent; apical pair usually well developed and decussate, only a little smaller than the discals. Laterally, pleuron with mostly dark brown ground colour and silver-grey pollinose. Larger bristles mostly black, finer hairs and setulae pale brown or golden, except for a patch of fine black hairs dorsally on anepisternum; the fine hairs mostly with crinkly tips. 1–2 stout upcurved proepisternal bristles and 1–3 similar proepimeral bristles; katepisternum with 1 large and 1 small anterior bristle (the latter rarely missing) and 1 stout posterior; 1 large and several smaller anepimeral bristles; and a linear group of about 6–10 quite long but slender meral bristles, variously dark or pale, with a considerable number of associated pale hairs; katepimeron haired.

Legs. Entirely pale brown except for occasional darkening around bases of femora. Bristles and setulae black, except for some golden ones on coxae and trochanters and to a varying extent posteriorly on all femora. Forefemur with

conspicuous d, pd, and pv rows of long stout hairs; foretibia with 1–2 p bristles and occasionally 1–2 pd, also a row of small, barely differentiated, spiny ad bristles on about the basal half, and pv, d and ad preapical bristles, the first 2 stout but the last much smaller, often scarcely differentiated. Midfemur usually with a stout spine anteriorly near centre (absent in about 10% of specimens), 2–3 preapical pd of graded lengths, and pv row of stout bristles; about 10% of specimens also with 1–3 stout hairs differentiated in a sub-basal av row; midtibia with stout ad and v near centre (rarely with 1–2 smaller, more basal ad) and 2–3 p or pd bristles; also preapical ad and pd and about 6 apicals of various lengths, the av and pv usually the stoutest. Hindfemur with ad row of long hairs, an av row usually with a distinct “gap” past centre, and a pv row on basal half only; hindtibia with conspicuous, comb-like row of short, rather spiny ad bristles, including 1 longer one near centre; also 1 stout and 0–3 smaller av, 1 stout and 1–2 smaller pd, 1 stout preapical d, 1 shorter but stout preapical ad and an apical av spine; Pd1/Sdd 0.7–1.1, mean 0.53.

Wing. Membrane tinged with brown across a broad area at base, covering basal cells and extending through costal and subcostal cells and faintly along vein R2+3; veins pale brown to brown over most of their length, darkening apically; tegula and basicosta typically pale brown (occasionally mid brown), the latter paler than the former. Swollen base of vein R4+5 with 1–6 setulae dorsally, 1–5 ventrally. Costa setulose ventrally to apex of Sc. Crossvein r-m near centre of discal cell; vein M1+2 from i-m to bend a little shorter than or equal to i-m, but much longer than from bend to wing margin; bend rather sharply angled for a blondeliine. Calypters greyish to cream or pale gold, margins white to gold, with a tuft of pale golden, crinkly hairs at their external junction; lower calypter with posterior margin gently curved, its internal angle closely abutting scutellum.

Abdomen. All tergites black in ground colour, syntergite 1+2, and tergites 3 and 4, with lateral reddish brown areas that cover about 50% of the disc in both dorsal and ventral views, extending variably on to tergite 5. Tergites with silver to golden pollen, tending to become more golden on posterior segments, but absent on a narrow dark median vitta over most or all of tergites 3 and 4, and sometimes tergite 5. A pair of

median submarginal bristles (rarely with 1–2 supplementary bristles) almost always present on both syntergite 1+2 and tergite 3. Sternite 4 black with black hairs, other sternites scarcely visible. Hairs and setulae all black on dorsum, except for occasional pale ones on tergite 5; ventrally, pale brown or golden, except along margins of tergites, variably on disc of tergite 5, and on sternites 3 and 4.

Terminalia (Figs 5–7). Ground colour pale brown. In lateral view, surstyli with apices slightly surpassing those of cerci, somewhat variable in shape, but usually digitate with rounded apex, often slightly curved in a posterior direction; cerci of a similar shape. In posterior view, surstyli with their apices slightly curved outwards; cerci separated basally by a rather broad, V-shaped notch; apex with a short row of medial teeth.

Female. Similar to male, differing essentially as follows: Head width 4.0–4.4, mean 4.13 mm; approximately 3 times as wide as frons.Anterior surfaces with golden pollen, except on face. Outer vertical bristles and ocellar bristles well developed, as are 2 stout proclinate orbital and 1 reclinate or lateroclinate (prevertical) bristles; anterior proclinate bristle rarely (c. 1%) absent on one side; reclinate upper orbital bristles usually rather fine and irregular, more clearly differentiated than in male, but still rather distinctive. More ventral parafacial setulae usually pale. Genal setulae usually all or almost all pale. Scutellum with more conspicuous pale grey or milky pollinosity; setulae all dark above but sometimes pale laterally at base and/or ventrolaterally. Foretibia with spiny bristles in ad row much more prominent and of graded lengths. Midfemur with 2–9 spiny bristles of various sizes anteriorly near centre, and 1–3 stout av hairs towards base; midtibia with 1–2 smaller ad bristle basal to the large, stout one. Hindtibia with spines in ad row sparser and longer, and usually with 2 longer members. Wing with up to 8 setulae on base of vein Rs. Abdomen usually all dark in dorsal view except for a pale area, of variable extent, at apex of tergite 5; in ventral view mainly dark, except for posterior apical bands on tergites, sometimes with pale areas of variable extent laterally on the tergites; visible sternites (usually just sternite 5) pale brown; pollinosity, especially on tergite 5, bright to pale golden, narrow median dark vitta barely or not at all represented.

Terminalia. Forming an extensible tube about 1.5 times as long as tergite 5; segment 6 very finely sclerotized, but setose on apical half; segment 7 rather more heavily sclerotized, tergite 7 consisting of a pair of narrow hemitergites, sternite 7 a simple scoop-like structure with rounded apex.

Distribution. Qld, NSW, ACT, Vic., Tas, and WA; no doubt in SA also.

Biology. My abundant material of F. wentworthi has one most striking feature: the great majority of specimens have been reared. In my experience this is most unusual in Tachinidae, which are commonly taken also at light, in traps, or by hand-netting—as, indeed, is the case with the closely related F. vicina sp. nov. (but not other members of the group, which resemble wentworthi in this respect). I see no obvious reason for this phenomenon. It may be fortuitous: Dr Monty Wood has recently netted several specimens by

“hilltopping”. For F. wentworthi, the host in every case is a pergid sawfly—especially Perga affinis Kirby, but also Pergagrapta polita (Leach), Pergagrapta bella (Newman), Pergagrapta gravenhorstii (Westwood), Pergagrapta spinolae (Westwood), Perga dorsalis Leach, and Pseudoperga sp.

Field observations of F. wentworthi by Dr Carne and (especially) Mr M. F. Leask (all in MSS) state that the adult fly lays an egg in a skin-fold on the mature sawfly larva, by protruding its ovipositor forward ventrally between its legs to a quite remarkable distance, swaying back and forth to avoid the violent strokes of the host’s abdomen. Eventually, the ovipositor makes contact and an egg is laid. This account is difficult to reconcile with the length of the ovipositor in dissections; while obviously extensile to some degree, it seems unlikely to attain even the length of the abdomen. Such behaviour would be possible for some species of Anagonia, but these observers would hardly mistake a chrysomelid larva for that of a sawfly. I am unable to explain the apparent discrepancy.

In the laboratory, the fly emerges from the host cocoon usually after some 3–5 months; but as few as 2 months, and as many as 10, have been recorded.

Notes. Malloch’s holotype of wentworthi is very well preserved, and seems clearly conspecific with the species just described. However, it has one remarkable idiosyncrasy: both hindtibiae lack the preapical ad bristle. In several hundred specimens of what I am here calling F. wentworthi, I have seen only one similar specimen. I have to conclude that Malloch’s unique specimen was, by a remarkable coincidence, an extremely rare variant.