Sturmiopsis parastica Curran, 1939

Barraclough, D. A., 2004, A taxonomic review of Sturmiopsis Townsend, 1916, an Old World genus of Tachinidae (Diptera) parasitising economically significant lepidopterous stem borers, African Invertebrates 45 (1991), pp. 7-20 : 13-17

Sturmiopsis parastica Curran, 1939

Figs 2–5 , 7–12

Rhodesina parasitica Curran, 1939: 3 .

Curranomyia parasitica: Townsend 1941: 115 .

Sturmiopsis parasitica: Mesnil 1952: 228, 1959: 11 ; Crosskey 1980: 880, 1984: 286.

Sturmiopsis angustifrons Mesnil, 1959: 11 ; Crosskey 1980: 880, 1984: 290. Syn. n.

Type material examined: Rhodesina parasitica : Holotype _ ( AMNH): ZIMBABWE: ‘ Rhodesina / parasitica / Curran.? / Holotype’ [rectangular red card]; ‘Salisbury / S. Rhodesia. / Dept.Agric. / DEC 1933 ’; ‘3587’. In fair condition; right fore and mid legs missing; fore tarsus detached; postabdomen dissected. An incomplete puparium is mounted with the adult. Paratype ^ (labelled allotype) ( AMNH): same locality data, numbered 1016. Sturmiopsis angustifrons : Holotype _ ( SMNS): TANZANIA: ‘Kisangara / 31.xii–1.i.1952 / D.O. Afrika Exp.’ [black type on rectangular blue card]; ‘ Sturmiopsis / angustifrons Mesn. / L. Mesnil det., 1958’; ‘TYPE’ [black type on rectangular red card]. In excellent condition; postabdomen dissected.

Redescription:

Male:

Dimensions (mm): Body length 3.6–5.1 (4.1); wing length 4.7–5.7 (5.2).

Colour/pollinosity: Head mainly dark brown or black with silver pollinosity. Parafrontal sometimes noticeably darker than mesofrons; both with silver or brown pollinosity. Parafacial yellow or brown pollinose; face indistinctly silver or yellow pollinose, ground colour sometimes yellow at lower extent.Antenna entirely dark brown to black, although sometimes irregularly paler; some specimens with A.s.1 and A.s.2 yellow and ventral half to four­fifths of A.s.3 yellow or dark orange, although in other specimens these antennal sections only slightly or partly or irregularly paler. Gena dark yellow­brown to brown (usually somewhat paler than parafacial and lower occiput), indistinctly silver or pale brown pollinose. Palp yellow­brown to brown. Thorax almost entirely dark brown to black, but postalar callus and posterior margin of scutum sometimes indistinctly paler and lateral and posterior margins of scutellum (sometimes posterior tip ranging to apical two­thirds) yellow­brown; pollinosity almost entirely silver, but sometimes partly pale yellow on scutellum; pollinosity noticeably denser on mesonotum and scutellum. Legs almost entirely dark brown to black. Wing completely hyaline, veins yellowish. Abdominal T 1+2 and T 3 mainly blackish, although sometimes yellow­brown laterally (rarely markedly so). T 4 dark yellow­brown to black, sometimes with indistinct blackish dorsomedial vitta, and rarely with yellow­brown lateral margins; T 5 similar, but without dorsomedial vitta.Abdominal dorsum with silver pollinosity clearly evident on anterior quarter to three­fifths of T 3– T 5, darker sections of dorsum typically with brown pollinosity visible upon rotation.

Head ( Figs 3–5 ): Outer verticals about two­fifths to half length of inner verticals; 2 (rarely 3) moderately developed reclinate orbital setae, both shorter than inner verticals, and inserted just anterior to ocellar triangle. Parafrontal hairing relatively profuse and short to moderately elongate, sometimes reaching about half length of frontal setae. Parafacial hairing sometimes slightly sparser than that on parafrontal; present on upper four­fifths to almost entire height. A.s.2 elongate, about two­thirds to three­quarters length of A.s.3. Third aristal segment swollen in about basal one­quarter to two­fifths, maximum width subequal to or noticeably broader than that of basal aristomeres. Palp broader apically, here reaching 1.5–2.5 X basal width; apical extremity acutely pointed. Eye with inconspicuous, short, sparse hairing (hairs often about 2–3 ommatidia apart), hairs sometimes restricted to posterior two­thirds of eye, or hairing completely absent.

Wing ( Fig. 2 ): Margin with subcostal spine sometimes differentiated, albeit small. Basal node of R 4+5 with 2–3 setulae. Cell r 5 narrowly open at margin, distance along costa 0.3–1.0 X length of r­m. Bend of M smoothly rounded (sometimes abruptly so), nearly always without short appendix, bend positioned close to wing margin, distance about one­fifth to one­third distance from m­cu. Vein m­cu positioned half to two­thirds distance from r­m to bend of M.

Abdomen: T 3 with paired median marginal setae. T 4 with complete marginal setal row, this extended ventrally. T 5 with setae on posterior quarter to half, including discals.

Postabdomen ( Figs 7–12 ): Cercus simple, not dorsally ridged medially, longer than surstylus in profile; hairing on lateral margins distributed on posterior one­fifth, longest hairs at posterior margin, these reaching about three­quarters length of entire cercus. Surstylus (Southern and East African population) ( Figs 7–10 ): Flat along dorsal margin in profile, although sometimes slightly sinuous; acutely rounded (sharply to broadly) apically; somewhat broader basally or slightly broader at mid­length. Hairs always present, although not on apical one­fifth, usually present on apical two to four­fifths; hairing restricted to ventral half, length of hairs ranging from short to elongate with longest hairs distributed along ventral margin, length of these reaching depth of surstylus in profile. Surstylus (West African population) ( Figs 11–12 ): Vestiture similar, albeit ventral hairs somewhat shorter; shape different, dorsal margin concavely curved at about basal one­third of length, ventral margin with moderate to marked convex flexure at about apical one­third.

Puparial spiracles: Small and flat, slightly raised above surface. Each spiracle comprising 2–3 clusters of serpentine ridges and with striking black perimeter. Spiracles closely approximated, sometimes virtually contiguous or separated by about one­ to two­thirds width of each spiracle.

Female (differences from male):

Dimensions (mm): Body length 3.2–4.8; wing length 3.9–5.5.

Colour/Pollinosity: Head pollinosity completely silver, this usually strikingly dense on parafrontal and parafacial. Facial region and facial ridge sometimes largely yellowbrown.

Head: Parafrontal with 2 proclinate and 1 reclinate orbital setae, posterior proclinate orbital closer to insertion of reclinate orbital than that of anterior proclinate orbital; parafrontal hairs short, at most about one­fifth length of frontal setae. Parafacial hairing often sparse. Palp conspicuously swollen apically (club­shaped), apical extremity smoothly rounded, apical region at broadest extent slightly more than 3.5 X width of base, although sometimes noticeably narrower apically (width here reaching about 2.5 X that of base).

Remarks:According to Mesnil (1959), his new species Sturmiopsis angustifrons differed from S. parasitica by having a pair of strong median marginal setae on T 3, the eyes almost bare, the occiput without black ‘microchetae’ on its upper part behind the postocular row, and the second antennal segment yellow. I have examined the holotypes of both S. parasitica and S. angustifrons and have concluded that the suite of character states of S. angustifrons fall within the variational range of a widened concept of S. parasitica , and that S. angustifrons is thus a junior synonym of S. parasitica . There is no significant difference in the development of the T 3 median marginal setae as stated by Mesnil (1959: 11). Mesnil also insinuated that S. parasitica had eyes with significantly more hairing than S. angustifrons . This is incorrect; the holotype of angustifrons has discernible—albeit short—hairing on its posterior two­thirds (although hairs largely absent on its anterior third), while that of parasitica has comparable short hairing over much of its surface. In a wider concept of S. parasitica the eyes range from having irregularly scattered short hairing (hair length subequal to the width of two ommatidia, e.g. Fig. 5 ) over the entire surface of the eye, to being completely bare; this is quite unlike S. inferens where the eyes are nearly always obviously haired, with the length of the hairs often reaching the width of four to five ommatidia. Mesnil is correct in stating that the holotype of angustifrons differs in having black occipital setulae present behind the upper part of the postocular row (only pale hairing is evident in the holotype of parasitica ). However this is of no taxonomic significance, as there are sometimes only one or two black occipital setulae present in some specimens. The holotype of S. angustifrons does have the antenna (especially the first two segments) extensively pale, unlike that of S. parasitica where the antenna is completely dark. There are, however, numerous intermediate colour forms, and a wider concept of S. parasitica thus has extensive intraspecific variation in antennal colour. In other respects the holotypes of angustifrons and parasitica differ in only a few minor colour characters. I have identified two forms of surstylus shape (see description above), one from Southern and East Africa (specimens from Zimbabwe, Tanzania and Kenya dissected) and the other from West Africa (specimens from Nigeria, Ghana and Senegal dissected). There is a small possibility that these disjunct populations could represent distinct species, although additional material needs to be examined and ideally corroborating character states identified. I have dissected both the holotypes of parasitica ( Fig. 7 ) and angustifrons ( Fig. 8 ), collected in Southern and East Africa respectively, and both have a surstylus of similar shape in profile. I have not figured the distribution of S. parasitica as I have not made an exhaustive study of all available material, and in any event collected material was sourced almost entirely from specimens reared by economic entomologists, and not collected in the field. An extensive recent search of the Natal Museum’s Diptera collection has not yielded any additional material, and I have not seen any field­collected material from South Africa, which is possibly outside the natural distribution of this species.

Other material examined: INDIA (introduced): 3 _2^, Bangalore, 11.x.1974, C.I.B.C., ex Chilo sp. ( AMNH). BENIN: 1^, ‘onne station?’, 22.iv.1991, ex Sesamia on maize ( BMNH). GHANA: 1 _ and associated puparium, N. Kawie, 29.xii.1969, I. K. Maafo, ex Eldana saccharina (AMNH) ; 1^, Kpandu, Togoland, T. Volta, N. D. Jago, 28.xii.1959, to light ( BMNH); 2^, Kumasi, 1 with associated puparium, emerged 9.ii.1970, 25.ii.1970, I. K. Maafo, ex Eldana sacharrina (AMNH) ; 1 _ and associated puparium, same data except collected at Boni ( AMNH); 1 _, Obuasi, 7.vi.1991, ex Eldana saccharina on maize ( BMNH). KENYA: 1 _ and associated puparium, Kilifi, ‘Kaloleni: ex Chilo sp. ’, C.I.B.C. ( BMNH); 1^, Kilindini, Mombasa Island, L. F. Brown, 19–23.viii.1955 ( BMNH); 1^ and associated puparium, reared at Washington D.C., emerged 16.x.1946, ex phalaenid larva in Sorghum vulgare (probably Sesamia ) ( AMNH). NIGERIA: 1 _ and associated puparium, Ibadan, 7.vi.1991, J. A. Ubeku, on maize, ex Eldana saccharina , pupa(ted) 13–14.vi.1991, em(erged) 25–27.vi.1991 ( BMNH); 1^ and associated puparium, Ibadan, 22.viii.1960, F. A. S., in gamba grass, ex Coniesta larva ( BMNH); 1 _1^, Samaru, Zaria, 25.ix.1959, ex pupa Coniesta ignefusalis (BMNH) ; 1 _, ix.1972, C.I.B.C., ex Eldana saccharina on sugarcane ( AMNH). SENEGAL: 1^, 15 mls N. Kaolack, 18.viii.1985, R. H. Markham, ex Coniesta ignefusalis , millet ( AMNH); 1 _ and associated puparium, Nioro­du­Rip, x.1982, recovered from larvae of Acigona ignefusalis on pearl millet ( BMNH). TANZANIA: 1 _1^ (same mounting), 2 associated puparia, Mbeya, 14.v.1957, I.W.B. Nye, reared ex Busseola fusca (BMNH) ; 1^, Songea, iii.1966, J. E. D. Milner, ex B. fusca (BMNH) . ZIMBABWE: 1 _, Salisbury, ix.1956, C. N. Smithers, ex larva of Busseola fusca (BMNH) ; 1^, Salisbury Dist., 24.ii.1954, Dept.Agric., par. stalk borer ( BMNH); 1^, Sby. Expt. Stn., ix.1968, R. P. Mparutsa, parasite of Busseola fusca (NMSA) ; 2 _, 1 with associated puparium, Dept. Agric., 2.xii. & 25–27.xii.1953, parasite of stalk borer, (ex) Busseola fusca (BMNH, NMSA) .

Figures

Figs 1–2. Wing venation (apical two­thirds), showing positions of bend of M and m­cu. 1. Sturmiopsis emdeni. 2. Sturmiopsis parasitica. [Not to scale].

Fig. 3. Sturmiopsis parasitica; male holotype, head in profile (vestiture on antenna, eye, occiput and gena omitted).

Fig. 4. Sturmiopsis parasitica; frontal view of antennae, showing relatively elongate second segment, and pubescent third aristal segment, which is swollen in about basal one­third. Note vestiture on adjacent parafacials and setae restricted to lower half of facial ridges. [SEM micrograph; scale as indicated].

Fig. 5. Sturmiopsis parasitica; SEM micrograph showing part of male eye in lateral view, with reduced distribution of relatively widely separated, short hairs. [SEM micrograph; scale as indicated]

Figs 6–12. Male terminalia in profile (vestiture usually shown on surstylus only) in specimens from selected localities. 6. Sturmiopsis emdeni. 7–12. Sturmiopsis parasitica. 7. Holotype of S. parasitica (Zimbabwe). 8. Cercus and surstylus, holotype of S. angustifrons (Tanzania). 9. Surstylus (Tanzania). 10. Surstylus (Kenya). 11. Surstylus (Nigeria). 12. Surstylus (Ghana). Scale = 1.0 mm.