Stilobezzia (Acanthohelea) tridentis, Cazorla and Spinelli, 2014

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, pp. 1-55 : 41-44

Stilobezzia (Acanthohelea) tridentis, Cazorla and Spinelli sp. nov.

( Figures 13, 19)

Diagnosis

The only Patagonian species of Stilobezzia (Acanthohelea) in which males have aedeagal sclerites with a short distolateral process and distal portion curved with a basal tooth and tip pointed. Females sternite 8 large and globose, and spermathecae sclerotized with hyaline punctuations.

Male. Head ( Figure 13A). Dark brown. Antennal flagellum dark brown; plume dark brown, well developed; antennal ratio 1.12–1.22 (1.18, n = 3). Palpus dark brown; segment 3 slightly shorter than 5; palpal ratio 2.66–3.60 (3.14, n = 5).

Thorax ( Figure 13B). Scutum dark brown; scutellum pale brown with 7–8 large setae; postscutellum dark brown. Legs stout, dark brown, hind leg darker; hind tibial comb with 9 spines; prothoracic TR 1.70–1.90 (1.83, n = 5); mesothoracic TR 2.09– 2.36 (2.20, n = 5); metathoracic TR 2.00–2.28 (2.14, n = 5). Wing ( Figure 13C) length 1.45–1.92 (1.78, n = 5) mm, width 0.52–0.69 (0.64, n = 5) mm, costal ratio 0.70–0.75 (0.73, n = 6); membrane slightly infuscated; second radial cell 2.18–2.88 (2.56, n = 6) × longer than first; cubital fork originating distal to base of r-m cross vein; macrotrichia on costa, R 1, R 2, R 3, M 1, M 2, sparse on cells r 3, m 1. Halter whitish.

Abdomen. Dark brown. Genitalia ( Figures 13D, E): tergite 9 extending 0.91 of gonocoxite length, narrowing distad, posterior margin rounded with small pointed projection; sternite 9 3.90× broader than long; sternite 10, narrowing distad, extending slightly beyond apex of cerci; cerci slender, divergent. Gonocoxite stout, two times longer than greatest breadth, inner margin with anteromesal blunt tubercle, gonostylus 1.33× shorter than gonocoxite, slightly curved, basal 1/4 wide, narrowing to pointed tip. Parameres slightly sclerotized, subparallel; stem stout, rounded tip. Aedeagus 1.20× longer than basal breadth; composed of two heavily sclerotized sclerites, each with anterior portion stout, straight, with short distolateral process; distal portion curved with basal tooth, tip pointed.

Female. Head ( Figure 13F). Antennal ratio 1.34–1.69 (1.55, n = 8); palpal ratio 3.00– 3.10 (3.05, n = 8). Mandible with 7 coarse teeth.

Thorax. Scutum dark brown, humeral pits pale brown; scutellum pale brown with 7–8 large, 2 thinner setae; prothoracic TR 1.75–2.00 (1.87, n = 8); mesothoracic TR 2.08–2.36 (2.21, n = 8); metathoracic TR. 1.91–2.25 (2.12, n = 8). Wing ( Figure 13G) length 1.76–1.86 (1.82, n = 8) mm, width 0.70–0.76 (0.73, n = 8) mm, costal ratio 0.71–0.77 (0.75, n = 10); membrane slightly infuscated; second radial cell 2.70–3.57 (3.06, n = 7) × 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 y CuA 2, abundant on distal half of cells r 3, m 1, sparse on cells m 2, cua 1.

Abdomen. Dark brown, segments 7–8 slightly darker. Genitalia ( Figure 13H): sternite 8 large, anterior margin convex, lateral margins subparallel, posteromedian excavation deep, V-shaped; sternite 10 with 4–5 pairs of setae, cerci short, rounded; two globose, heavily sclerotized spermathecae with hyaline punctuations with nearly imperceptible necks, measuring 7.40–9.20 (8.40, n = 5) by 5.50–7.70 (6.40, n = 5) µm and 4.80–7.40 (6.20, n = 5) by 3.70–5.70 (4.70, n = 5) µm; plus a third rudimentary spermatheca.

Distribution

Argentina (Neuquen, Río Negro); Chile (Malleco, Chiloé) ( Figure 19).

Types

Holotype male, allotype female, Chile, Malleco prov., Cordillera de Las Raíces, 40 km E de Curacautín, 1650 m, 5 February 979, D. and M. Davies – B. Akerbergs ( MLPA). Other paratypes: 7 males, 14 females, as follows: Argentina, Neuquen prov., Parque Nacional Nahuel Huapi , lago Espejo , 40°38 ′ 49.3 ″ S, 71°42 ′ 12.7 ″ W, 903 m, 23 February to 5 March 2008, A. Garré – F. Montes de Oca , 2 males, 2 females, Malaise trap; Río Negro prov., Parque Nacional Nahuel Huapi, río Manso superior, 41°14 ′ 8.1 ″ S, 71°46 ′ 58.5 ″ W, 845 m, 7 February to 2 March 2007, A. Garré – F. Montes de Oca , 7 females (one in BMNH, one in USNM), 2 males (one in BMNH, one in USNM), Malaise trap; same data except 41°14 ′ 28.4 ″ S, 71°44 ′ 12.6 ″ W, 837 m, 1 female, 2 males; same data except La Cantera, 41°21 ′ 16 ″ S, 71°42 ′ 27.3 ″ W, 764 m, 15 January to 7 February 2007, A. Garré – F. Montes de Oca , 2 males, Malaise trap; Parque Nacional Nahuel Huapi, laguna Mercedes, 40°52 ′ 43.4 ″ S, 71° 34 ′ 41 ″ W, 899 m, 3–21 January 2008, A. Garré – F. Montes de Oca , 1 female, Malaise trap; Chile, Chiloé prov. , Huillinco, 4 December 1984, J. A. Downes, 3 females, sweep net (JAD 1722/1/22; 1690/4/43; 1691/2/58) ( CNCI).

Etymology

The name tridentis refers the particular shape of the aedeagal sclerites.

Discussion

This species is similar to S. (A.) nigerrima . However, S. nigerrima differs by the thorax uniformly dark brown, the sternite 8 of females with V-shaped posteromedian excavation and the slender aedeagal sclerites, which are nearly straight with recurved basal arms and truncate tip.