Stilobezzia (Acanthohelea) rava 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 : 186-189

Stilobezzia (Acanthohelea) rava Ingram and Macfie, 1931

( Figures 10 , 18 )

Stilobezzia rava Ingram and Macfie, 1931: 203 (female, male; Argentina). Stilobezzia (Neostilobezzia) rava: Das Gupta and Wirth , ver 1968: 142 (in list); Wirth, 1974: 43 (in catalogue of New World species south of USA).

Stilobezzia (Acanthohelea) rava: Borkent and Wirth, 1997: 109 (in World catalogue); Borkent and Spinelli, 2000: 53 (in catalogue of species of southern USA); Borkent and Spinelli, 2007: 86 (in Neotropical synopsis); Borkent, 2014: 136 (in online World catalogue).

Diagnosis

The only Patagonian species of Stilobezzia (Acanthohelea) large and dark, in which males have scutum dark brown to blackish except the humeral pits pale brown and scutellum pale brown with 13–18 long, large setae and 8–10 thinner, short setae. Females scutum dark brown to yellowish brown except humeral pits and posteromesal portion yellowish, and pyriform spermathecae with hyaline punctuations.

Male. Head ( Figure 10A ). Dark brown. Antennal flagellum dark brown, flagellomeres 1–10 with mesal pale ring; plume dark brown, dense; antennal ratio 1.63–1.78 (1.70, n = 10). Palpus dark brown, segment 3 slightly longer than 5; palpal ratio 3.50– 4.33 (3.88, n = 10).

Thorax ( Figure 10C ). Scutum dark brown to blackish, humeral pits pale brown; scutellum pale brown with 13–18 long, large, 8–10 thinner, short setae; postscutellum dark brown to blackish. Legs with dense setae, yellowish brown; coxae dark brown; hind femur, apex of hind tibia darker, stouter; tibia with 3–4 apical spines; hind tibial comb with 8 spines; prothoracic TR 1.74–2.08 (1.82, n = 10), mesothoracic TR 1.90– 2.33 (2.12, n = 10), metathoracic TR 1.75–2.30 (1.87, n = 10). Wing ( Figure 10B ) length 2.33–2.75 (2.52, n = 10) mm, width 0.75–0.93 (0.85, n = 10) mm, costal ratio 0.72–0.77 (0.74, n = 10); membrane slightly infuscated; second radial cell 2.86–3.72 (3.30, n = 10) × longer than first; cubital fork originating at level to base of r-m cross vein; macrotrichia on costa, R 1, R 2, R 3, M 1, marginal on cell r 3, sparse on apex of cell m 1. Halter pale.

Abdomen. Dark brown; genitalia ( Figure 10D ): massive, as broad as abdominal segment 8, dark brown, with dense setae; tergite 9 extending to apex of gonocoxites, posterior margin nearly straight with membranous posterolateral extension; sternite 9 4.00× broader than long, with narrow, shallow posteromedian excavation; sternite 10 elongated, produced beyond base of cerci; cerci slender, divergent. Gonocoxite stout, 1.50× longer than greatest breadth, inner margin with mesal pointed tubercle; gonostylus slightly shorter than gonocoxite, nearly straight, tip rounded. Parameres subparallel, slightly sclerotized, basal apodemes slender; stem rod-like, tip spoon-shaped. A small triangular sclerite located at proximal 1/3 of stem of parameres. Aedeagus 0.60× length of basal breadth, composed of two slender, sinuous sclerites, each with basal portion curved, slightly broadening to tip.

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

Head ( Figure 10E ). Antennal flagellum dark brown, base of flagellomeres slightly paler; antennal ratio 1.40–1.75 (1.56, n = 8); palpal ratio 3.43–4.18 (3.76, n = 10). Mandible with 7 coarse teeth.

Thorax. Scutum dark brown to yellowish brown, humeral pits, posteromesal portion yellowish; scutellum pale brown with 9–14 large, 8–12 thinner setae; postscutellum dark brown; pleura dark brown except katepisternum pale brown. Legs yellowish brown, with dense setae, distal 1/2 of hind femur, apex of hind tibia darker ( Figure 10G ); hind tibia with dorsal row of long, dark setae; hind tibial comb with 9 spines; prothoracic TR 1.69–2.17 (1.99, n = 10); mesothoracic TR 1.94–2.22 (2.15, n = 10); metathoracic TR 1.88–2.30 (2.00, n = 10). Wing ( Figure 10F ) length 2.28– 2.92 (2.51, n = 10) mm, width 0.98 (0.89–1.13, n = 10) mm¸ costal ratio 0.74–0.81 (0.77, n = 10); second radial cell 2.77–4.18 (3.42, n = 10) × longer than first; membrane infuscated; cubital fork originating slightly distal to base of r-m cross vein; macrotrichia on costa, R 1, R 2, R 3, M 1, M 2, abundant on distal 1/2 of cell r 3, 1/3 of cell m 1, sparse on cell m 2.

Abdomen. Brown, segment 8 darker. Genitalia ( Figure 10H ) anterior margin of sternite 8 straight, sclerotized, lateral margins divergent, posteromedian excavation V-shaped, sternite 10 with 5 pairs of setae; cerci short, rounded; two pyriform spermathecae with hyaline punctuations and short, very slender necks, measuring 10.00–12.90 (11.00, n = 8) by 5.90–9.60 (9.60, n = 8) µm and 8.00–11.00 (9.82, n = 8) by 7.00–9.60 (7.83, n = 8) µm, plus a rudimentary third spermatheca.

Distribution

Argentina (Neuquen, Río Negro, Tierra del Fuego) , Chile (Llanquihue, Magallanes) ( Figure 18 ) .

Types

Holotype male, Chile, Llanquihue prov. , Casa Pangue, 4–10 December 1926, P. and M. Edwards; allotype female, same data as holotype except 20–22 November 1926; 1 paratype male, same data as allotype ( BMNH).

Other specimens examined

Argentina: Neuquen prov., Parque Nacional Nahuel Huapi, mallin La Heladera, 41° 00 ′ 56 ″ S, 71°49 ′ 45.4 ″ W, 878 m, 15 December 2006 to 7 January 2007, A. Garré – F. Montes de Oca – J. Massaferro, 2 males, Malaise trap ; Río Negro prov., Estación Biológica Puerto Blest , 6–15 January 2007, 1 male, light trap ; Tierra del Fuego prov., Parque Nacional Tierra del Fuego, 7–9 December 2005, G. Spinelli, 3 males, 3 females, Malaise trap; Paso Garibaldi, 2 March 1993, G. Spinelli, 1 male, sweep net; Bahía Lapataia , 24–28 February 1997, P. Posadas, 1 female, Malaise trap; 7–9 December 2005, G. Spinelli, 1 female, Malaise trap .

Chile: Magallanes prov., isla Deceit, 19–27 November 1982, D. Lanfranco, 13 males, 8 females, Malaise trap; Bahia Scourfield , 17–25 February 1980, D. Lanfranco, 9 females, Malaise trap; Punta Arenas, 23 November 1961, T. Cekalovic, 1 male, sweep net .

Discussion

This species is somewhat similar to S. succinea . However, S. succinea differs by the general coloration yellowish brown. Males have smaller antennal ratio, the wing is shorter and the genitalia is less massive, not as broad as abdominal segment 8. The female sternite 10 bears 5–6 pairs of setae and the spermathecae are different, one globose, the other ovoid.

Figures

Figure 10. Stilobezzia (A.) rava Ingram and Macfie: (A–D) male; (A) head; (B) wing; (C) scutum and scutellum (dorsal view); (D) genitalia (ventral view), aedeagus and parameres removed. (E–H) female; (E) head; (F) wing; (G) hind leg; (H) genitalia. Scale bars 0.05 mm.

Figure 18. Distribution of Stilobezzia (A.) mapuche, Stilobezzia (A.) patagonica and Stilobezzia (A.) rava.