Delia ventralis (Stein, 1914)

Ackland, D. M., 2008, Revision of Afrotropical Delia Robineau-Desvoidy, 1830 (Diptera: Anthomyiidae), with descriptions of six new species, African Invertebrates 49 (1), pp. 1-75 : 36-41

Delia ventralis (Stein, 1914)

Figs 46 , 50–55

Chortophila ventralis Stein, 1914: 135 ; 1919: 154.

Hylemyia ventralis (Stein) : Malloch 1924 b: 262, 264; Emden 1941 b: 266; 1951: 362; 1956: 530; Paterson 1956: 164.

Delia ventralis (Stein) : Pont & Ackland 1980: 717.

Diagnosis:

♂ Abdomen with tergites III and IV posteriorly excavated, separated from each other and from tergites II and V by areas of membrane; sternite III ( Fig. 52 ) bearing long setae on posterior margin, which are either erect or depressed against sternite IV; sternite V processes ( Fig. 52 ) with long apical setae (longer than length of processes).

Description:

Male.

Colour: Frontal stripe, parafrontals, parafacials and genae varying from orange-brown to blackish (with whitish brown dusting), parafacials viewed from in front sometimes slightly bronzy, without sheen stripe on parafrontal angle; face and occiput black (with greyish to brownish dust).Antennae entirely dark brown to black. Palpi black; prementum thinly dusted brownish, slightly shining. Thorax mainly black in ground colour, varying from thinly greyish brown dusting on pleura (a few sclerites slightly shining) to scutum rather densely brownish dusted with faint brownish vittae when viewed from in front; scutum viewed from behind with wide brownish median vitta bordered by two paler narrow dusted vittae between acr and dc rows; lateral declivities pale dusted.Abdomen varying from black to brownish with shifting darker median vitta which becomes diffused on tergites III and IV on whole width of tergites; pregenital sclerite brownish, thinly dusted; hypopygium thinly dusted.Wing membrane weakly greyish brown tinged, more strongly so basally; wing bases with brownish veins, not contrasting with membrane; squamae paler than wing base with rather distinct yellow border; halteres orange-yellow. Legs blackish brown, thinly dusted.

Head: Eyes without evident pubescence, separated by width of anterior ocellus; frontal stripe linear at narrowest point, widening anteriorly to about 1.5× width of parafacial at this level; parafrontals narrow posteriorly; parafacials about as wide as postpedicel; peristomal margin in lateral view not projecting beyond level of parafrontal angle; gena below lowest point of eye margin 0.2–0.25× eye height; 7–8 pairs of parafrontal setae on slightly more than anterior half of distance between antennal base and anterior ocellus; interfrontal setae well developed, at least half length of frontal setae; genal setae biserial with 2–3 upcurved setulae above lower row. Postpedicel 1.8–2.0 times as long as wide, apex not quite reaching peristomal margin; arista with short pubescence, longest hairs (on dorsal surface) 1.3–1.5× diameter of aristal base. Prementum short (not longer than depth of gena) and not swollen. Palpi slender. Occiput with an extra row of setulae below upper postocular setae.

Thorax: 2+3 dc; 3(–4) pairs of presutural acr (anterior pairs longest), rows close together, acr: dc ratio 10:4:10; 1+1 posthumerals; notopleural depression bare apart from two long setae; prealar 0.5–0.7× length of posterior npl and slightly finer (specimens from Kenya with prealar short and fine, 0.2× length of posterior npl); scutellum with its dorsal surface largely bare (only about 2–6 setulae on disc laterally within area bound by basal and subapical scutellars; anepisternite without developed upper anterior setulae; proepisternal depression bare; katepisternals 1+2, lower posterior seta nearly as long as upper.

Wing: Vein C with rather strong marginal spinules (those between costal breaks about 1.5–2 times as long as C width, with pair before distal break more than twice as long; lower crossvein straight, joining M 1+2 rectangularly to slightly oblique; last section of M 1+2 1.8–1.9× length of preceding section. Lower squama not projecting beyond upper. Wing length 4.5–5.0 mm.

Legs: Mid femur with row of 4–6 pv on basal half (basal av short and weak); hind femur with complete row of av, only 1–2 pv apically; fore tibia with a small ad and a slightly longer pv, no blunt pv apical; mid tibia with 1 ad, 1 pd, 2 p / pv; hind tibia with 2 av, 4 ad, 3 pd, 0–1 pv; mid tarsomere 1 without outstanding dorsal setulae. Pulvilli on fore legs nearly as long as tarsomere 5.

Abdomen: About 2.2–2.3 times as long as greatest width at hind margin of tergite III, dorsoventrally compressed, tergites III and IV short and posteriorly excavated, separated from each other and from tergites II and V by wide areas of flexible intersegmental cuticle; ssternite III ( Fig. 52 ) longer than wide (about 2.5–3.0 times as long as wide), with hind margin expanded slightly and bearing long setae (longer than length of sternite); these setae are slender with fine curved tips, and are longer laterally, being much shorter medially and tending to form two groups. (Note: these setae may be either flattened against sternite, when they are sometimes difficult to see, or else erect and projecting vertically at right angles from sternite, probably associated with pheromone dispersal during courtship; see Figs 70, 71 .) Sternite IV ( Fig. 52 ) wide with only short setulae, in lateral view tips reaching past hind margin of tergite IV; sternite V processes ( Fig. 52 ) with lateral setae becoming longer distally where they are much longer than length of processes; inner margins of processes with only fine hairs. Surstyli in caudal view ( Fig. 50 ) expanded medially, becoming slender in apical third; in lateral view ( Fig. 51 ) slightly sinuate. Cercal plate short and wide (1.2 times as long as wide), with rounded apical margin bearing 6–8 setae which are not as long as cercal plate. Pregonite bearing 2 short setae on distal margin; postgonite triangular without setae. Aedeagus with distal section ( Fig. 55 ) about 1.5× length of aedeagal apodeme, divided on more than distal third (0.43×) by pair of free paraphallic processes and dorsal prolongation mainly membranous.Acrophallus absent.Aedeagal apodeme in dorsal view expanded anteriorly, excavated on dorsal surface, 2.25 times as long as greatest width. Ejaculatory apodeme 0.33× length of aedeagal apodeme.

Female.

Colour: Head dark as in male, parafacial without sheen stripe on orbits/parafacial area; frontal stripe entirely orange-brown or infuscated posteriorly. Thorax, abdomen and wing membrane as in male.

Head: Eyes widely separated (by 1.6–1.7× their transverse width). Frontal stripe at level of middle orbital setae 1.7–1.8 times as wide as parafrontal; which widens anteriorly to about 1.3× width of postpedicel. Three pairs of orbital setae outwardly directed; 3 pairs of frontal setae, placed in a line with orbitals; crossed interfrontal setae well developed, placed at apex of frontal triangle. Prementum as in male but slightly more robust.

Thorax: Katepisternals 1+2, lower posterior seta nearly as long as upper.

Wing length up to 6 mm.

Legs: Mid femur with only 1–2 pv, no av; hind femur with 3–5 av (rather short), 1–2 pv, no av; fore tibia with 1 ad, 1 pv; mid tibia with 1 ad, 1 pd, 2 p / pv; hind tibia with 1–2 av, 4 ad, 3 pd, 1 pv.

Abdomen: Postabdomen when fully extended as long as preabdomen. Tergites VI and VII largely reduced to pairs of dorsocentral plates, continuous across dorsal surface only along posterior margins of segments where they bear rows of rather long setulae; 6th and 7th spiracles both posteriorly situated on segment VI (6th more or less at edge of tergite VI, 7th within posteroventral corners of tergite VI); sternite VIII ( Fig. 46 ) represented by pair of short sclerites which are widely separated and converge anteriorly, bearing several setulae; sternite X rather small; cerci long and slender, extending well beyond posterior margin of sternite X by length of sternite X; 3 spermathecae of more or less equal size (about 0.03–0.04 mm).

Types of D. ventralis unknown, presumed lost.

Material examined: KENYA: Aberdare Range, 1 ♂ Mt Kinangop , 8000 ft, x.1934, J. Ford ( BMNH) ; 4 ♂ Nyeri Track , 10500 ft, ii.1934, F.W. Edwards ( BMNH) ; 2 ♂ Mt Elgon , heath zone , 10500–11500 ft, ii.1935, F.W. Edwards ( BME Afr. Exped.) ( BMNH) ; 1 ♂ Mt Elgon, Kathita R ., 9900 ft, 9.vii.1949, J.A. Riley ( OUEC Exped., 1949) ( BMNH) . UGANDA: Ruwenzori Range: 1 ♂ Mt Karangora , 9900 ft, xi.1934 – i.1935, F.W. Edwards; 15 ♂ 16♀Namwamba Valley , 11000 ft, xii.1924 – i.1935, E.G. Gibbons; 1 ♂ 11000–12000 ft, xii.1934 – i.1935, F.W. Edwards ( BME Afr. Exped., 1935); 1 ♂ Bigo , 11400 ft, 20–22.vii.1952, D. S. Fletcher (Ruwenzori Exped., 1952); Mt Elgon , 1 ♂ Balirungi , 11200 ft, 1.viii.1952; 2 ♂ Bulambuli , 9500 ft, viii.1934, J. Ford; 1♀same locality, 8.viii.1934, on Lobelia aberdarica, J. Ford ; 2♀between Butandiga & Bulambuli , 8000 ft, 7.viii.1934, J. Ford (all BMNH) .

Discussion: D. ventralis was described from ‘7 ♂ and several ♀’, from the bamboo forest at 2870 m on Mount Kenya. Stein states in the original description that sternite II [= sternite III] is elongated and armed on the posterior margin, with a row of long erect hairs pointing downwards. Emden (1951: 362) drew attention to these ventral setae, and figured the abdomen of a male of the species he recognised as ventralis . The type material of ventralis was collected on an expedition to East Africa by Ch. Alluaud and R. Jeannel (from 1911–12) (Stein 1914). No mention is made in the publication of the deposition of any of the material collected; presumably it is in Paris. I have been unable to locate it, and Dr A.C. Pont, who has visited the MNHN, informs me it is not there; nor are there any syntypes amongst material from Stein’s collection in ZMHU.

The material of D. ventralis in the BMNH (identified mainly by Emden) consists of two closely related species, both having long setae on sternite III. They are separated in the male sex mainly by the nature and length of these setae, and also those on sternite V. Following the figure of the abdomen in Emden (1951) I have applied the name ventralis to this species (longer setae), and have named the other (shorter setae) as pseudoventralis sp. n. It should be noted that the species renamed as steiniella by Emden also has long setae on sternite III in the male; this species has differently shaped surstyli, and more distinct vittae on the scutum. Emden (1951: 362) lists a record of “ ventralis ” from Natal, Weenen, H.P. Thomasset (in BMNH). I have been unable to find this specimen, but it is probably the species described in this paper as D. ismayi sp. n. Other specimens of ismayi from S. Africa have also been named “ ventralis ” by Emden, and I have seen no specimens of ventralis further south than Kenya and Uganda, though it may well occur in Tanzania.

Drew (1963: 249) listed “ Hylemya ventralis (Stein) ” as a North American species first described as Chortophila ventralis by Stein (1914). This is incorrect. The North American species was first described as Hylemyia ventralis by Stein in 1920. Currently the North American (and Japanese) species is known by the subsequent name Delia pectinor Suwa (1984) to avoid secondary homonymy. It has no relevance to the present Afrotropical species (see Griffiths 1993: 1447).

Life history: Unknown.

Distribution: D. ventralis appears to be confined to Equatorial Africa; all of the material I have seen is from Uganda and Kenya, generally at high altitudes, ranging from 2438 to 3658 m. D. ventralis occurs in Kenya on Mt Elgon, Mt Kenya (type locality), and the Aberdares. D. pseudoventralis sp. n. also occurs on all these ranges. However, D. ventralis is the only one of these two species recorded from the far west of Uganda in the Ruwenzori Range.

Figures

Figs 44–49. Delia spp., female abdomen, terminal segments, ventral view: (44) D. bracata (Zimbabwe); (45) D. arambourgi (Kenya); (46) D. ventralis (Uganda); (47) D. steiniella (Ethiopia); (48) D. kigeziana (Uganda); (49) D. tibila sp. n., female paratype (Ethiopia). Scale bar = 0.1 mm.

Figs 50–55. Delia ventralis, male (Uganda): (50) cercal plate and surstyli; (51) ditto, lateral view; (52) sternites III–V; (53) sternites III–IV, lateral view; (54) gonites; (55) distiphallus, lateral view. Scale bar = 0.1 mm.

Figs 70–71. Diagram of sternal hinging mechanism in the Delia ventralis subsection: (70) sternite III with setae depressed; (71) ditto, setae erect. Arrow indicates direction of movement of sternite II.