Delia modesta (Stein, 1914) Ackland, 2008

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 : 72-73

Delia modesta (Stein, 1914) , comb. n.

Hylemyia modesta Stein, 1914: 133 ; 1919: 151; Malloch 1924 b: 263, 265; Emden 1941 b: 268; 1956: 530; Pont & Ackland 1980: 718.

Stein described modesta from 4 ♂ and 4♀from 4 localities in Kenya. The important characters in his description of the male were:

Gena 0.1–0.13 of eye height; thorax clear chocolate, matt, with 3 wide vittae which are a little darker but scarcely visible; prealar absent; acr very fine and very short, biserial; katepisternals 1+2; abdomen linear, very narrow and elongated, dorsoventrally compressed, dusted greyish chocolate; mid tibia with 1 ad, 2 pd, 2 p setae; hind femur with complete rows of long fine setae; squamae whitish yellow.

Malloch (1924 b: 265) had not seen this species, but this did not deter him from including it in a key, using some of the characters mentioned in Stein’s description. Emden (1941 b: 268) also failed to recognise this species. He mentioned the lack of a prealar seta, and the narrow genae.

Emden (1956: 530) mentioned a pair from Gatsibu ( Ruanda) which (in his opinion) fitted Stein’s description very well; he continued by listing several characters by which the male specimen from Gatsibu differed from Stein’s description:

Abdomen only depressed at base.

Sternites II–IV with rather long erect setulose hairs in 2–3 irregular rows, more numerous and less strong than in echinata (Séguy).

Fore tibia in addition to a pv near middle, with a smaller one near apical one-fifth and a small ad beyond middle.

Mid tibia with 1 pd and 2 p setae.

Hind tibia with 3–4 ad, 3 pd, 2(–3) av, the proximal ad and pd being smaller “and have apparently been overlooked by Stein” [They would not have been overlooked if Stein’s species was different to Emden’s specimen].

Of the female of this pair Emden said: “The ♀has a shifting spot on upper part of parafacial like arambourgi (= flavibasis )”. It is unlikely that the male from Gatsibu is modesta in view of the differences from Stein’s description, in which the hind tibia have 2 ad and 2 pd. Unfortunately, of this pair from Gatsibu, which were deposited in the MRAC in Tervuren (Brussels), only the female can now be found (communication from Dr M. De Meyer). It carries the following label:

“ COLL. MUS. CONGO / Ruanda : Gatsibu / 1800m. terr. Biumba/ P. Basilewsky 6-11-53” [white printed rectangular label]; “ Hylemyia / modesta Stein / van Emden det. 1955” [white printed/handwritten rectangular label] .

This female is in poor condition, right antennae, right mid leg missing; left wing damaged along costa; right fore leg glued to polyporus mounting strip. This is a female of Delia flavibasis (Stein) .The specimen has the following characters which are contrary to Stein’s description of modesta but agree with flavibasis :

Colour: Parafacials opposite base of antennae with a darker brownish orange shifting patch (sheen-stripe); scutum with distinct brown spots around bases of setae. Wing membrane faintly tinged light brownish.

Head: Gena below lowest point of eye margin 0.2× eye height.

Thorax: 3 pairs of short and fine presutural acr, biserial, no hairs between rows; acr: dc ratio 10:6:10. Wing: large crossvein slightly sinuate. Legs: fore tibia with 1 ad, 2 pv; mid tibia apparently without av, 1 strong ad (pd not visible); hind femur with about 4– 5 av in distal half, no pv except 1 apical; hind tibia with 2 av, 4 ad, 3 pd, no pv.

Discussion: In common with both Malloch and Emden, I have not seen any male specimens from Kenya that agree sufficiently with Stein’s description. The only Afrotropical Delia species which could be modesta is D. madagascariensis described in this paper. The male of this species has rather narrow genae (0.17–0.20× eye height), hind tibia with 2 ad and 2 pd, prealar absent. Until further material (especially males) is available from the African mainland, I prefer not to synonymize these species; in the meantime modesta remains an unrecognized species.