Stilobezzia (Acanthohelea) megatheca 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 : 18-21

Stilobezzia (Acanthohelea) megatheca Cazorla and Spinelli sp. nov.

( Figures 5, 17)

Diagnosis

The only Patagonian species of Stilobezzia (Acanthohelea) in which males have the posterior margin of tergite 9 with a small, rounded, hyaline projection. Females have two large, greatly elongated flask-shaped spermathecae and sternite 8 with a Ushaped posteromedian excavation.

Male. Head ( Figure 5A). Dark brown. Antennal flagellum dark brown; plume dark brown, poorly developed; antennal ratio 1.50–1.91 (1.69, n = 13). Palpus brown; segment 3 as long as 5; palpal ratio 3.16–3.80 (3.41, n = 24).

Thorax ( Figure 5C). Scutum dark brown, humeral pits pale yellowish; scutellum pale yellowish with 6 large setae; postscutellum dark brown. Legs uniformly brown; hind tibial comb with 7 spines; prothoracic TR 1.73–1.92 (1.84, n = 25); mesothoracic TR 2.00–2.33 (2.13, n = 23); metathoracic TR 1.79–1.92 (1.87, n = 26). Wing ( Figure 5B) length 1.64–2.03 (1.70, n = 26) mm, width 0.58–0.67 (0.62, n = 26) mm, costal ratio 0.68– 0.74 (0.72, n = 10); membrane slightly infuscated; second radial cell 2.78–3.83 (3.11, n = 13) × longer than first; cubital fork originating slightly distal to base of r-m cross vein; macrotrichia on costa, R 1, R 3, M 1, M 2, wing margin, sparse on cells r 3, m 1. Halter pale.

Abdomen. Dark brown. Genitalia ( Figure 5D): tergite 9 extending 0.92 of gonocoxite length, posterior margin rounded with small, hyaline, rounded projection; sternite 9 4.3× broader than long, with broad, deep, posteromedian excavation; sternite 10 narrow, spiculate, extending to base of cerci; cerci slender, divergent. Gonocoxite 1.27× longer than greatest breadth, inner margin with anteromesal pointed tubercle; gonostylus slightly shorter than gonocoxite, stout, nearly straight, with dorsal subapical bulk; tip heavily sclerotized, beak-like, sharply pointed, tip pointed, heavily sclerotized, directed anteriorly. Parameres contiguous anteriorly, slightly divergent distally, basal apodemes slightly curved; each with stem rod-shaped, tip bulbous. A small triangular sclerite located just anterior to base of parameres. Aedeagus 0.66× length of basal breadth, composed of two slender, sinuous sclerites, each with proximal portion curved laterad, tips pointed, separated.

Female. Smaller, similar to male, with the following notable differences:

Head ( Figure 5E). Dark brown. Antennal flagellum brown; antennal ratio 1.33– 1.51 (1.39, n = 8); palpal ratio 2.75–3.95 (2.96, n = 10). Mandible with 7 coarse teeth.

Thorax. Scutellum with 5 large, 3 thinner setae. Legs prothoracic TR 1.73–1.90 (1.81, n = 9); mesothoracic TR 2.08–2.30 (2.16, n = 9); metathoracic TR 2.00–2.30 (2.17, n = 8). Wing ( Figure 5F) length 1.34–1.68 (1.51, n = 10) mm, width 0.60 (0.55– 0.66, n = 10) mm; costal ratio 0.66–0.73 (0.70, n = 9); membrane slightly infuscated; second radial cell 2.12–2.85 (2.5, n = 10) × longer than first; macrotrichia on costa, R 1, R 2, M 1, M 2, CuA 2, abundant on distal 1/3 of cells r 3, m 1, sparse on cell m 2.

Abdomen ( Figure 5G). Anterior margin of sternite 8 straight, lateral margins subparallel; posteromedian excavation U-shaped, shallow; sternite 10 with 4–5 pairs of setae; cerci rounded. Two large, greatly elongated, flask-shaped spermathecae with short necks, measuring 22.30–26.10 (24.40, n = 10) by 3.70–9.20 (7.20, n = 10) µm and 18.90–23.70 (21.90, n = 10) by 5.50–7.70 (6.60, n = 10) µm; plus a third small, ovoid spermathecae measuring 3.60–6.20 (4.80, n = 10) µm.

Distribution

Argentina (Neuquen, Río Negro, Chubut), Chile (Valdivia, Osorno, Llanquihue, Chiloé) ( Figure 17)

Types

Holotype male, allotype female, Argentina, Neuquen prov., Villa La Angostura, 11– 15 January 2004, G. Spinelli, light trap ( MLPA). Other paratypes: 39 males, 24 females, as follows: Argentina, Neuquen prov., lago Aluminé , 22 December 1996 to 3 January 1997, 1 male, D. Podestá, Malaise trap; cerro Chapelco , sobre lago Lacar , 27 November 1984, J. A. Downes, 5 males, sweep net (JAD 1653/1/6,18, 20; 1653/2/ 17,19) ( CNCI); lago Lolog , 24 November 1984, J. A. Downes, 2 males, sweep net (JAD 1651/3/13,14,28) ( CNCI); Río Negro prov., El Bolsón, 29 December 1999, G. Spinelli, 1 male, light trap; río Villegas , 57 km S Bariloche, 8–3 December 1994, L. Quate, 1 male, Malaise trap; lago Gutiérrez, January 2003, J. Liotta, 9 males, light trap; lago Gutiérrez, 20 January 2006, Grogan and Spinelli, 1 male, sweep net; arroyo Los Notros, 20 km O Bariloche, 26–28 November 1994, L. Quate, 4 males, Malaise trap; Parque Nacional Nahuel Huapi, arroyo Ñireco (Complejo Challhuaco) 41°11 ′ 51.9 ″ S, 71°19 ′ 40.5 ″ W, 962 m, 23 January to 18 February 2007, Garré and Montes de Oca , 1 male, Malaise trap; Chubut prov., Parque Nacional Los Alerces, margen E lago Futalaufquen, 20 January 1988, G. Spinelli, 2 males, 1 female, sweep net; Parque Nacional Los Alerces, 9–12 December 1994, L. Quate, 5 males, Malaise trap; Parque Nacional Los Alerces, arroyo s/n 2 February 2005, M. Donato, 1 male, sweep net.

Chile, Valdivia prov. , Fundo San Martín, 15 November 1984, J. A. Downes, sweep net, 2 females (JAD 1669/1/5; 1670/3/6) ( CNCI) ; Osorno prov. , Pucatrihue, 30 December 1992, G. Spinelli, 1 male, 1 female, sweep net ( USNM) ; same data except 1 December 1992, 1 female; Llanquihue prov. , Yerbas Buenas , 13 km N Ensenada , 1–6 December 1994, L. Quate, 2 males, light trap ; 3 km N Ensenada , 1–2 December 1994, L. Quate, 1 male, 5 females, Malaise trap ; same data except 4 December 1994, 1 female; road to Los Ulmos , 29 December 1984, J. A. Downes, 5 females, sweep net (JAD 1685/2/12,13,14,37,38) ( CNCI) ; Ensenada , 11 December 1984, J. A. Downes, 2 males, sweep net (JAD 1695/1/4; 1695/5/2) ( CNCI) ; Chiloé prov. , Ancud, 1 January 1985, J. A. Downes, 1 female, sweep net (JAD 1688/3/15) ( CNCI) ; Huillinco , 2 January 1985, J. A. Downes, 3 females, sweep net (JAD 1689/2/3,4,5) ( CNCI) ; same data except 3 January 1985, J. A. Downes, 1 female, (JAD 1690/4/48) ( CNCI) ; same data except 4 January 1985, 3 females, (JAD 1691/2/44) ( CNCI) .

Etymology

The name megatheca refers to the unique, conspicuous, greatly elongated flaskshaped spermathecae.

Discussion

This species is somewhat similar to S. (A.) estepae . Characters for distinguishing both species are in the discussion section of that species.