Stilobezzia (Acanthohelea) hirsuta Ingram and Macfie, 1931

Cazorla, Carla G. & Spinelli, Gustavo R., 2014, A revision of the Patagonian predaceous midges of the subgenus Acanthohelea of Stilobezzia excluding the S. (A.) edwardsi group (Diptera: Ceratopogonidae), Journal of Natural History 49 (3), pp. 155-209 : 167-169

Stilobezzia (Acanthohelea) hirsuta Ingram and Macfie, 1931

( Figures 3 , 17 )

Stilobezzia hirsuta Ingram and Macfie, 1931: 201 (female; Bariloche).

Stilobezzia (Neostilobezzia) hirsuta: Das Gupta and Wirth, 1968: 140 (in list); Wirth, 1974: 43 (in catalogue of New World species south of USA).

Stilobezzia (Acanthohelea) hirsuta: Spinelli and Wirth, 1993:5 1 (in list; Argentina); Borkent and Wirth, 1997: 108 (in World catalogue); Borkent and Spinelli, 2000: 52 (in catalogue of species of southern USA); Borkent and Spinelli, 2007: 85 (in Neotropical synopsis); Borkent, 2014: 134 (in online World catalogue).

Diagnosis

The only Patagonian species of Stilobezzia (Acanthohelea) that is large (male wing length 2.75–3.03 mm; female wing length 2.38–2.80 mm), with the body completely covered with long, coarse setae and tarsomeres 1–2 of all legs bearing two apical spines. Males sternite 9 with a posteromedian hyaline projection and posterior margin of tergite 9 bilobate. Females scutellum with 10–12 large and 8–10 thinner setae.

Male ( Figure 3A ). Head. Dark brown. Antennal flagellum brown; plume dark brown, poorly developed; antennal ratio 1.10–1.16 (1.13, n = 2). Palpus dark brown; segment 3 cylindrical, slightly shorter than 1; palpal ratio 4.14–4.57 (4.35, n = 3).

Thorax ( Figure 3C, D ). Scutum dark brown except humeral pits, lateral margins, two sublateral longitudinal bands, prescutellar depression yellowish; scutellum yellowish with 28–30 large setae in two rows; postscutellum dark brown, narrow lateral margin yellowish; pleura yellowish brown, distal half of katepisternum dark brown, proximal half yellowish. Legs dark brown, with dense, coarse setae; apex of hind tibia slightly darker; hind femur, tibia greatly enlarged, femur swollen; tarsomeres 1–2 of all leg with two apical spines; tarsomere 1 of hind leg with ventral row of spines; hind tibial comb with 11 spines; prothoracic TR 1.84–2.05 (1.96, n = 3), mesothoracic TR 2.05–2.22 (2.12, n = 3), metathoracic TR 1.90–2.15 (2.03, n = 3). Wing ( Figure 3B ) length 2.75–3.03 (2.89, n = 3) mm, width 0.93–0.98 (0.95, n = 3) mm, costal ratio 0.75–0.79 (0.77, n = 3); membrane deeply infuscated; second radial cell 3.54–4.40 (4.00, n = 3) × longer than first; cubital fork originating at level of base of r-m cross vein; macrotrichia on costa, R 1, R 2, M 1, sparse on cells r 3, m 1. Halter pale.

Abdomen. Dark brown, with dense, large, setae. Genitalia ( Figure 3E, F ): tergite 9 extending slightly beyond apex of gonocoxite, posterior margin bilobate, each lobe with slender lateral membranous extension; sternite 9 1.47× broader than long, with posteromedian hyaline projection. Gonocoxite 1.30× longer than greatest breadth, inner margin with mesal pointed tubercle; gonostylus stout, heavily sclerotized, nearly straight, tip rounded. Parameres subparallel, basal apodemes slender; stem rodshaped, apical 1/3 slightly broader, tip truncate. Aedeagus 0.50× length of basal breadth, composed of two convergent, slightly sclerotized sclerites, each slender, sinuous with distal portion curved, tip pointed.

Female. Similar to male, with the following notable differences:

Head ( Figure 3G ). Antennal flagellum dark brown, bases slightly paler; antennal ratio 1.48–1.64 (1.56, n = 3); palpal ratio 3.57–4.14 (3.85, n = 3). Mandible with 7–8 coarse teeth.

Thorax. Scutellum with 10–12 large, 8–10 thinner setae. Legs pale brown; tarsomere 1 of mid leg with basal spine; prothoracic TR 1.87–2.06 (1.92, n = 3), mesothoracic TR 1.94–2.06 (2.02, n = 3), metathoracic TR 1.94–2.21 (2.06, n = 3). Wing ( Figure 3H ) length 2.38–2.80 (2.60, n = 3) mm, width 0.93–1.07 (1.02, n = 3) mm, costal ratio 0.75–0.80 (0.78, n = 3); second radial cell 3.00–3.25 (3.12, n = 3) × longer than first; cubital fork originating at level of base of r-m cross vein; macrotrichia on costa, R 1, R 2, R 3, M 1, M 2, Cua 2, abundant on cells r 3, m 1.

Abdomen. Genitalia ( Figure 3I ) sternite 8 heavily sclerotized, anterior margin straight, lateral margins subparallel, posteromedian excavation shallow, V-shaped; sternite 10 with 5 pairs of setae; cerci rounded; two globular spermathecae with very short, narrow necks, measuring 9.60–11.40 (10.80, n = 3) by 8.10–11.40 (9.70, n = 3) µm and 8.50–9.60 (9.20, n = 3) by 7.00–9.20 (7.90, n = 3) µm; plus a small third rudimentary spermatheca.

Distribution

Argentina (Río Negro, Tierra del Fuego) ( Figure 17 ) .

Types

Holotype male, allotype female, Argentina, Río Negro prov., Bariloche , 1 December 1926, P. and M. Edwards ( BMNH).

Other specimens examined

Argentina, Tierra del Fuego prov., Parque Nacional Tierra del Fuego, 7–9 December 2005, G. Spinelli, 2 males, 3 females, Malaise trap .; Río Negro prov., Parque Nacional Nahuel Huapi, lago Cántaros, 41°00 ′ 39.3 ″ S, 71°49 ′ 6.6 ″ W, 895 m, 13 January 2007, A. Garré – F. Montes de Oca , 1 male, sweep net .

Discussion

This species greatly resembles S. rava . However, males of S. rava differ by the tergite 9 that does not extend beyond the apex of the gonocoxites and its posterior margin is nearly straight. Females differ by the divergent lateral margins of the sternite 8 and by the pyriform spermathecae.

Remarks

Several males have a paler gonostylus than the holotype.

Figures

Figure 3. Stilobezzia (A.) hirsuta Ingram and Macfie: (A–F) male; (A) head; (B) wing; (C) thorax detail (lateral view); (D) thorax (lateral view); (E) abdomen; (F) genitalia (ventral view), detail of posteromedian projection of sternite 9, parameres removed and detail of posterior margin of tergite 9. (G–I) female; (G) head; (H) wing; (I) genitalia. Scale bars 0.05 mm.

Figure 17. Distribution of Stilobezzia (A.) hirsuta, Stilobezzia (A.) megatheca and Stilobezzia (A.) monomorphica.