Stilobezzia (Acanthohelea) monomorphica 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 : 21-24

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

( Figures 6, 17)

Diagnosis

The only Patagonian species of Stilobezzia (Acanthohelea) without normal secondary sexual dimorphism, and both sexes have a basal spine on tarsomere 1 of the hind leg. Males with gonostylus stout proximally, distal 2/3 curved, apical 1/3 abruptly tapered, tip slender and sharply pointed. Females scutum dark brown except humeral pits and mesal region yellowish, and small, greatly unequal-sized and globular spermathecae.

Male. Head. Dark brown. Antennal flagellum ( Figure 6A) dark brown female-like, without a plume; antennal ratio 1.40–1.54 (150, n = 4). Palpus dark brown; segment 3 subequal to 5; palpal ratio 3.33–4.20 (3.84, n = 4). Mandible with 6 coarse teeth.

Thorax ( Figure 6C). Scutum dark brown except humeral areas, lateral margins, prescutellar depression pale yellowish; scutellum pale yellowish with 15 large, 6–7 thinner setae; postscutellum dark brown; pleura light brown, antepisternum partially yellowish. Legs brown, with dense setae, hind leg stout, slightly darker; hind tibia with dorsal row of long setae; tarsomere 1 of hind leg with basal stout spine, tarsomeres 1–2 with two distal stout spines; tarsomere 5 as long as 3; hind tibial comb with 9 spines; prothoracic TR 2.00–2.07 (2.01, n = 4), mesothoracic TR 2.07–2.25 (2.15, n = 4), metathoracic TR 2.08–2.42 (2.18, n = 4). Wing ( Figure 6B) length 1.96–2.19 (2.08, n = 4) mm, width 0.74–0.84 (0.79, n = 4) mm, costal ratio 0.72–0.75 (0.74, n = 6); membrane slightly infuscated; second radial cell 3.00–5.20 (3.40, n = 4) × 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, sparse on distal half of cell r 3. Halter pale brown.

Abdomen. Dark brown, with dense setae. Genitalia ( Figure 6D): tergite 9 short, extending 0.80 of gonocoxite length, tapering gradually distally; sternite 9 4.30× broader than long; sternite 10 spiculate, produced slightly beyond base of cerci; cerci narrowly separated proximally, elongated, slender, apices divergent. Gonocoxite stout, 1.65× longer than greatest breadth; gonostylus 0.90× shorter than gonocoxite, heavily sclerotized, stout proximally, distal 2/3 curved, apical 1/3 abruptly tapered, tip, slender, sharply pointed. Parameres subparallel, basal apodemes slender, slightly curved; stem stout on proximal 1/2, distal halves rod like, apices swollen, blade-shaped. Aedeagus 0.68× length of basal breadth, composed of two nearly straight sclerites, each with basal portion recurved 60°, distal portion slightly broader, tip pointed, directed mesad.

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

Head ( Figure 6E). Antennal ratio 1.35–1.63 (1.44, n = 4). Palpal ratio 3.86–4.09, (3.96, n = 4).

Thorax. Scutum dark brown, humeral pits, mesal area yellowish. Scutellum with 12 large, 6–8 thinner setae; tarsi of foreleg, mid leg pale, tarsomeres 1–3 of mid leg with two distal spines; tarsomere 1 of hind leg ( Figure 6G) with two ventral row of setae; prothoracic TR 1.88–2.00 (1.93, n = 4), mesothoracic 2.04–2.15 (2.11, n = 4), metathoracic TR 1.88–2.38 (2.15, n = 4). Wing ( Figure 6F) length 2.02–2.54 (2.19, n = 4) mm, width 0.80–0.92 (0.85, n = 4) mm, costal ratio 0.74–0.76 (0.75, n = 4); membrane slightly infuscated; second radial cell 3.87–4.87 (4.15, n = 4) × longer than first; cubital fork originating slightly distal to level of base of r-m cross vein; macrotrichia on costa, R 1, R 2, R 3, M 1 and M 2, abundant on distal 1/3 of cell r 3, sparse on m 1. Halter pale.

Abdomen. Dark brown, with dense setae. Genitalia ( Figure 6H): anterior margin of sternite 8 convex, lateral margins slightly concave, posteromedian excavation shallow, V-shaped; sternite 10 with 5 pairs of setae, cerci short. Two globose, greatly unequal-sized spermathecae with nearly imperceptible necks, measuring 10.20–11.10 (10.70, n = 2) by 7.80–8.50 (8.10, n = 2) µm and 8.40–8.50 (8.40, n = 2) by 6.80–7.40 (7.10, n = 2) µm; plus a small third rudimentary spermatheca.

Distribution

Argentina (Neuquen, Río Negro) ( Figure 17) .

Types

Holotype male, allotype female, Argentina, Neuquen prov., Laguna Epulafquen, 21–23 February 2001, G. Spinelli, Malaise trap ( MLPA). Other paratypes: 5 males (one in CNCI, one in BMNH), 3 females (one in CNCI, one in BMNH), as follows: Argentina, Río Negro prov., Parque Nacional Nahuel Huapi, laguna los Clavos , 41°

04 ′ 48.6 ″ S, 71°49 ′ 33.9 ″ W, 1194 m, 5 February to 3 March 2007, A. Garré – F. Montes de Oca, Malaise trap.

Etymology

The specific name monomorphica refers to the lack of secondary sexual dimorphism in males of this species.

Discussion

This is the only species of Stilobezzia in the subgenus Acanthohelea without obvious male secondary sexual characters. The male genitalia of this new species greatly resembles those of S. (A.) varia , but males of that species differ by their broader sternite 9, with a broad, shallow posteromedian excavation, a pale and slender gonostylus and a gonocoxite with a short, mesal tubercle.