Delia virgithorax (Stein, 1913)

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 : 70-72

Delia virgithorax (Stein, 1913)

Hylemyia virgithorax Stein, 1913: 556 ; 1919: 152; Emden 1951: 363.

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

Stein described H. virgithorax from 2♀. I was able to examine a specimen labelled ‘holotype’ in February 1995, loaned from the ZMHU.This is a syntype that was retained by Stein in his personal collection. The female syntype examined in 1951 by Emden (1951: 363) was sent to him by Dr A. Soós from the MNM and was destroyed in 1956, along with many other Anthomyiidae . I made a description of the female syntype in Berlin as follows:

Labels : ♀syntype: “ Abyssinia / Kovács”. [white printed rectangular label]; “Dire-Daua / 1911.11.19 ” [white written /printed rectangular label]; “Zool. Mus. / Berlin” [pale yellow printed label]; “ Hylemyia / virgithorax St. ” [white written rectangular label] ( ZMHU). In good condition, all appendages present except left hind leg missing .

Colour: Head rather densely pale grey dusted, including occiput. Gena anteriorly with shifting patch, pale orange-brown from some angles. Interfrontalia orange-brown. Antennae brown, basal segments lightened reddish. Palpi dark brown, obscurely reddish brown basally. Mentum brown with greyish dust, hardly shining. Thorax pale greyish dusted, scutum viewed from in front with very distinct dark brownish median vitta, half width of distance between dc, reaching from 1st presutural dc to scutellum, becoming slightly wider posteriorly. Also pair of similar lateral vittae, their inner margins along the intra-alar setae, reaching from posthumeral setae to posthumeral callus; humeri and notopleuron grey dusted. Scutellum grey dusted. These vittae do not alter when scutum is viewed from behind. Pleura and postnotum grey dusted. Wings membrane, veins and squamae yellow to pale orange-yellow tinged, especially anteriorly.Squamae and halteres yellowish. Abdomen grey dusted, with brown median vitta, narrow posteriorly, but widening anteriorly on each tergite.

Head: Eyes separated at level of ocellar triangle by nearly 0.5× head width. Interfrontalia at middle with slightly concave margins, width at narrowest part equal to twice width of adjacent parafrontal. A pair of cruciate interfrontal setae, about as long and strong as the upper orbital setae; 3 orbitals, 3 frontal setae. Occipital setulae very short and fine, in one row.Postpedicel 2.4times as long as wide, not reaching peristomal margin.Arista pubescent, hairs slightly longer than diameter of aristal base. Gena in lateral view nearly 0.3× head height, genal setae uniserial. Palpi as long as prementum, latter not swollen but rather wide, in lateral view three times as long as wide, length 2/3 of eye height.

Thorax: acr practically absent, only represented by a very few irregular fine biserial hairs, rows slightly closer to each other than to dc rows, only a pair of prescutellar acr visible. Whole of scutum with very few accessory setulae or hairs. Prealar seta absent. No dorsal anterior anepisternal setulae present. Katepisternals 1+2, lower posterior 3/4 length of upper. Scutellum practically bare on disc.

Wing:Vein C bare on ventral surface, anterior spinules as long as diameter of vein, stronger setae before distal break as long as small crossvein. Large crossvein rather upright, hence ratio of penultimate section of M 1+2 to last section is 4:6. Wing length 5 mm.

Legs: Fore tibia with 1 av, 1 ad, and 1 pv. Mid tibia with 1 long ad, which is 2.5 times as long as diameter of tibia, 2 shorter pd, and 2 small p setae. Mid femur with only 1 short basal av. Hind femur with 7–8 short av, no pv except 1 apical seta. Hind tibia with 2 av, 4 ad, 4 pd, 4–5 very short pv. All pulvilli very short, hardly as long as claws.

Abdomen: Setae on posterior margins of tergites rather weak and short, especially tergites IV and V, where they are hardly half length of tergites.

Discussion: Emden (1941 a: 214) mentions 1 ♂ of virgithorax (collected on the Entomological expedition to Abyssinia, 1926–7) from Abyssinia, Mount Zukwala, ca. 900 ft, 22.x. by sweeping rushes in lake (Omer-Cooper); 1♀Jem-Jem Forest, nearly 9000 ft, 24.ix. (Scott). He also stated that it was known from Kilimanjaro, Mt Elgon, Mt Kenya, Aberdares, Kikuyu Esc. (R.E.).All these records refer to D. steiniella Emden , and are listed under that species.

Emden (1941 b: 266 in key) incorrectly synonymized Hylemyia trivittata Stein, 1914 with H. virgithorax Stein, 1913 , in the belief that there was only one species with a trivittate scutum, and that the absence of a prealar seta in virgithorax was abnormal. He corrected this synonymy in 1951 (Emden 1951: 361). In the same paper he gave the new name steiniella for H. trivittata Stein, 1914 , not Pegomyia trivittata Stein, 1897 (see under D. steiniella for full details).

No other specimens of D. virgithorax (apart from the types) have therefore been recorded, and the species is known only from the female syntype. I have not seen any males which could be referred to virgithorax .

Differentiation of the females of D. steiniella from D. virgithorax , the latter in parentheses:

Colour: Interfrontalia dark brown posteriorly (orange-brown); scutum with median vitta continuing onto scutellum (to scutellum); wing membrane and veins greyish brown (yellow to orange-yellow tinged).

Head: Interfrontalia with straight margins (slightly concave margins); occiput with short setulae below upper postocular row (bare); 3–4 rows of distinct presutural acr (practically absent, only a few irregularly fine hairs); prealar short but distinct (absent); katepisternals 1+2, lower posterior seta 0.75× length of upper seta.

Life history: Unknown.

Distribution: Only known from the type locality in Ethiopia.