Stilobezzia (Acanthohelea) bicinctipes 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, pp. 1-55 : 6-9

Stilobezzia (Acanthohelea) bicinctipes Ingram and Macfie, 1931

( Figures 1, 16)

Stilobezzia bicinctipes Ingram and Macfie, 1931: 195 (female, Chile)

Stilobezzia (Neostilobezzia) bicinctipes: Das Gupta and Wirth, 1968: 138 (in list); Wirth, 1974: 43 (in catalogue of New World species south of USA).

Stilobezzia (Acanthohelea) bicinctipes: Borkent and Wirth, 1997: 107 (in World catalogue); Borkent and Spinelli, 2000: 52 (in catalogue of southern USA species); Borkent and Spinelli, 2007, 85 (in Neotropical synopsis); Borkent, 2014: 133 (in online World catalogue).

Diagnosis

The only Patagonian species of Stilobezzia (Acanthohelea) in which both sexes have a conspicuous mid brown band on the hind femur, the forecoxa is pale and the mid and hind coxae are dark brown. Males hind tarsal claw enlarged, similar to female and parameres’ stem subtriangular. Females abdominal sternite 8 broader than long, anterior margin straight, lateral margins slightly divergent, with a deep, V-shaped posteromedian excavation.

Male. Head ( Figure 1A). Dark brown. Antennal flagellum brown; plume dark brown, dense; antennal ratio 0.95–1.02 (0.99, n = 3). Palpus brown; segment 3 slightly longer than 5; palpal ratio 2.90–3.20 (3.00, n = 3).

Thorax. Scutum dark brown, humeral pits yellowish; scutellum yellowish with 6 large, 2 thinner setae; postscutellum, pleura dark brown. Legs pale yellowish, hind leg darker; forecoxa pale, mid, hind coxae dark brown; hind femur with broad mesal brown band, distal half of hind tibia dark brown; hind tibial comb with 8 spines; tarsomere 1 of hind leg with stout basal spine; hind claw enlarged, similar to female; prothoracic TR 2.16–2.25 (2.22, n = 3); mesothoracic TR 2.48–2.61 (2.54, n = 3); metathoracic TR 2.40–2.65 (2.53, n = 3). Wing ( Figure 1B) length 1.50–1.52 (1.51, n = 3) mm, width 0.48–0.52 (0.50, n = 3) mm, costal ratio 0.70–0.76 (0.73, n = 3); membrane slightly infuscated; second radial cell 3.00–3.50 (3.3, n = 3) × longer than first; cubital fork originating slightly distal to level of base of r-m cross vein; macrotrichia on costa, R 1, R 2, M 1, marginal, sparse on cells r 3, m 1, m 2. Halter pale.

Abdomen. Dark brown. Genitalia ( Figure 1C): tergite 9 extending 0.77 of gonocoxite length, posterior margin rounded; sternite 9 four times broader than long, with shallow posteromedian excavation; sternite 10 spiculate, wide, produced beyond base of cerci; cerci slender, divergent. Gonocoxite 1.8× longer than greatest breadth, broadest proximally; inner margin with mesal pointed tubercle; gonostylus slightly shorter than gonocoxite, nearly straight, tip bluntly rounded. Parameres subparallel, basal apodemes slender; stem subtriangular, wide proximally, narrowing progressively to pointed tip. Aedeagus as long as broad, composed of two slightly curved sclerites, closely approximated subapically, with recurved tips.

Female. Similar to male, but larger with the following notable sexual differences: Head ( Figure 1D). Antennal ratio 1.31–1.49 (1.48, n = 9); palpal ratio 3.33–4.16 (3.82, n = 12). Mandible with 6–7 coarse teeth.

Thorax ( Figure 1E). Scutum dark brown, two dorsolateral pale yellowish bands extending from yellowish humeral pits. Scutellum with 8–9 large, 4 thinner setae. Legs yellowish; femorotibial joints dark; hind femur ( Figure 1G), with one mesal, one apical dark brown bands, distal half of hind tibia ( Figure 1H) dark brown with subapical yellowish brown ring; hind claws larger; prothoracic TR 1.75–1.94 (1.87, n = 12); mesothoracic TR 1.94–2.33 (2. 08, n = 12); metathoracic TR 2.43–3.00 (2.70, n = 12). Wing ( Figure 1F) length 2.08–2.88 (2.40, n = 12) mm, width 0.78–0.93 (0.83, n = 12) mm, costal ratio 0.79–0.83 (0.81, n = 10); second radial cell 3.75–5.62 (4.43, n = 10) × 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, sparse on margin of cells r 3, m 1, few on basal margin of m 2.

Abdomen. Pale brown, with dense setae. Genitalia ( Figure 1I): sternite 8 broader than long, anterior margin straight, lateral margins slightly divergent, nearly straight, posteromedian excavation deep, V-shaped; sternite 10 with 5 pairs of setae; cerci rounded. Two subspherical, heavily sclerotized spermathecae with slender, short necks, measuring 8.00–11.00 (9.40, n = 11) by 5.00–9.00 (7.90, n = 11) µm and 7.60–9.00 (8.90, n = 11) by 6.00–7.00 (6.70, n = 11) µm; plus a small rudimentary, third spermatheca, not visible in Figure 1I.

Distribution

Argentina (Río Negro), Chile (Valdivia, Osorno, Llanquihue, Chiloé) ( Figure 16).

Types

Holotype female, Chile, Llanquihue prov. , Casa Pangue, 4–10 December 1926, P. and M. Edwards ( BMNH).

Material examined

Argentina: Río Negro prov., Parque Nacional Nahuel Huapi, laguna Mercedes, 40° 52 ′ 43.4 ″ S, 71°34 ′ 41 ″ W, 899 m, 14 December 2007 to 3 January 2008, A. Garre – F. Montes de Oca , 3 females, Malaise trap; Estación Biológica Puerto Blest, 41°01 ′ 34.4 ″ S, 71°48 ′ 55.7 ″ W, 791 m, 6–13 January 2007, Garre and Montes de Oca , 3 females, at light .

Chile: Valdivia prov. , Valdivia, 3 December 1984, J. A. Downes, 2 females, sweep net (JAD 1658/1/9,10) ( CNCI) ; Fundo San Martín , 15 December 1984, J. A. Downes, 2 females, sweep net (JAD 1669/1/1; 1669/2/3) ( CNCI) ; Isla Teja , 3 December 1984, J. A. Downes, 2 females, sweep net (JAD 1657/1/8, 13) ( CNCI) ; same data except 13 December 1984, 1 female (1667/1/2) ( CNCI) ; Parque Nacional Puyehue , 12 December 1984, J. A. Downes, 1 female, sweep net (JAD 1666/1/10) ( CNCI) ; same data except 6/ 8 December 1994, J. A. Downes, 1 female, Malaise trap (JAD 1591/3/ 2) ; Osorno prov. , margen S lago Ranco 180 m, 28 November 1992, G. Spinelli, 1 female, sweep net ; Pucatrihue , 30 December 1992, G. Spinelli, 2 females, sweep net ( USNM) ; Llanquihue prov. , Las Cascadas, 13 km N Ensenada, 1–2 December 1994, L. Quate, 2 females (one in USNM) ; Yerbas Buenas , 13 km N Ensenada 1–6 December 1994, L. Quate, 1 female, sweep net ; road to Los Ulmos , 30 December 1984, J. A. Downes, 29 December 1984, 2 males, 2 females (JAD1685/2/5,3) (JAD1685/1/11,12) ( CNCI) ; same data except 1 males, 2 females, sweep net (JAD 1686/2/28, 29, 30) ( CNCI) ; Chiloé prov. , Huillinco, 4 January 1984, J. A. Downes, 1 female, sweep net (JAD 1691/2/42) ( CNCI) .

Discussion

This species resembles S. ornaticrus which also has legs with dark brown bands and a basal spine on hind tarsomere 1. Females of S. ornaticrus can be distinguished from those of S. bicinctipes by the sternite 8 with a convex anterior margin and U-shaped posteromedian excavation, and the spermathecae lack necks. In addition, males of S. ornaticrus have parameres with a rod-shaped stem, that is tapered distally and apically curved, and aedeagal sclerites with basal portion curved laterad and apex curved mesad with a pointed tip.

Remarks

Some of the studied specimens have poorly developed dorsolateral pale yellowish bands of the scutum and the subapical yellowish brown ring of the hind leg.

This is the first description of the male of Stilobezzia (A.) bicinctipes .