Type material: Holotype ♂: [Zimbabwe] Chikurubi [17°47′S 31°12′E]/806/10.10.50// Ex / Agrotis / segetis // COM. INST. ENT./ COLL. no. 12321 [BMNH]. Paratypes: 1 ♂, same data as holotype [BMNH]. 1 ♂, Angola, Changa, 21.–24.iii.1972, Southern African Exp. B.M. 1972-I [BMNH].

Etymology: Named after the English dipterist Roger W. Crosskey.

Description: Body length: 8–9 mm. Coloration and pruinescence: Head mostly black, except gena and anterior edge of parafacial which are red, covered with whitish-grey pruinescence. Palpus basally light-brown shading into yellow distally. Scape and pedicel varying from dark brown to fuscous red. Thorax mainly black; posterior 1/3–4/5 of scutellum reddish-yellow; postalar callus black or dark brown; scutum with four presutural dark vittae, lateral vitta distinctly outlined and ending wedgeshaped beside posthumeral seta. Legs black. Tegula and basicosta black or dark brown. Abdomen entirely black or slightly reddish laterally on tergites 3 and 4; tergite 3 with a transverse band of whitish-grey pruinescence on anterior 1/3–1/2, tergite 4 pruinose on anterior 2/3–4/5 (with shifting spots), tergite 5 on anterior 3/4–4/5.

Head: Compound eye densely covered with long ommatrichia, about as long as combined diameter of three to four facets. Arista thickened on basal 2/5–1/2. Second aristomere 6.3–8.5 times as long as wide. Thickened part of third aristomere about 0.7–1.0 times as long as second aristomere. Postpedicel 6.3– 6.9 times as long as pedicel. Vertex at its narrowest point 0.94–1.00 times as wide as compound eye in dorsal view. Lateral vertical seta not differentiated from postocular setae. Six to eight frontal setae descending below level of base of arista. Frontoorbital plate with one or two rows of medioclinate setae lateral to row of frontal setae. Gena in profile about 0.33 times as high as compound eye. Postocular setae fine, relatively long, curved anteriorly. Prementum about 1.0–1.5 times as long as wide.

Abdomen: Syntergite 1 + 2 with one pair of short and weak median marginal setae. Tergite 3 with one pair of median marginal setae about 1.3 times as long as corresponding tergite. Tergite 4 with a row of nine marginal setae. Tergite 5 with a row of marginal setae and several, very short, discal setae.

Male terminalia (Fig. 14A–D): Epandrium relatively long and convex. Cerci, not carinate, without brushlike setulae. Cerci, in lateral view, very slightly bent posteriorly (Fig. 14A). Posterior surface of distal 1/2 of cerci flat (Fig. 14C, D). Surstylus straight, very narrow in lateral view, apically pointed with a tuft of setae (Fig. 14D); surstylus, in posterior view, as in Figure 14B; posterior surface of surstylus not concave (Fig. 14A, C).

Notes: Dolichocolon crosskeyi is the only species of the genus characterized by having the compound eye covered with dense, long ommatrichia, thus making it easily distinguishable from all other congeners, even without the extraction of the male terminalia. The other two species with long ommatrichia are the Oriental D. dali and D. orientale, but in these species the ommatrichia are much more sparse.

Hosts: Agrotis segetum Denis & Schiffermüller (Lepidoptera: Noctuidae).

Distribution: Afrotropical: Angola, Zimbabwe.