Stilobezzia (Acanthohelea) ornaticrus 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 : 179-182

Stilobezzia (Acanthohelea) ornaticrus Ingram and Macfie, 1931

( Figures 7 , 19 )

Stilobezzia ornaticrus Ingram and Macfie, 1931: 194 (male; Chile).

Stilobezzia (Neostilobezzia) ornaticrus: Das Gupta and Wirth, 1968: 141 (in list); Wirth, 1974: 43 (in catalogue of New World species south of USA)

Stilobezzia (Acanthohelea) ornaticrus: Borkent and Wirth, 1997: 236 (in World catalogue); Borkent and Spinelli, 2000: 53 (in catalogue of species of southern USA); Borkent and Spinelli, 2007: 85 (in Neotropical synopsis); Borkent, 2014: 135 (in online World catalogue).

Diagnosis

The only Patagonian species of Stilobezzia (Acanthohelea) with yellowish brown legs, except hind femur dark brown with basal ring and distal 1/3 pale, scutellum yellowish with more than 25 large and 12 thinner setae. Males parameres rod-shaped, tapering distally to pointed, curved tip. Females sternite 8 rounded with U-shaped posteromedian excavation and spermathecae without neck.

Male. Head. Dark brown. Antennal flagellum dark, plume dense.

Thorax. Legs yellowish brown, hind femur dark brown except basal ring and distal 1/3 pale yellowish; coxae brown, hind coxa dark brown. Genitalia ( Figure 7B ): with dense, long setae, tergite 9 extending 0.80 of gonocoxite length, posterior margin rounded; sternite 9 3.40× broader than long, without posteromedian excavation; cerci not visible in the studied specimen. Gonocoxite stout, 0.68× length than greatest breadth, with basal portion broad; gonostylus shorter than gonocoxite, stout, nearly straight, pointed tip. Parameres subparallel, stem rod-shaped, tapering distally to pointed, curved tip. Aedeagus 0.63× length of basal breadth, composed of two slender sclerites, each with proximal portion curved laterad, tip pointed, curved mesad.

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

Head ( Figure 7C ). Dark brown. Antennal flagellum with flagellomeres dark brown except basal portion paler; antennal ratio 1.42–1.75 (1.59, n = 2). Palpus dark brown, segment 3 stout, as long as 5; palpal ratio 3.90–4.25 (4.07, n = 2). Mandible with 5/12 coarse teeth.

Thorax ( Figure 7E ). Scutum dark brown, humeral pits yellowish; scutellum yellowish with 15 large, 12 thinner setae; postscutellum dark brown; pleura dark brown. Legs pale brown, with dense setae; coxae dark brown, hind femur ( Figure 7F ) dark brown except narrow basal ring, distal 1/3 pale; hind tibia dark brown; hind tibial comb with 8 spines; tarsomere 1 of mid leg with 1 basal, 2–3 distal spines ( Figure 7G ); tarsomere 1 of hind leg with stout basal spine; prothoracic TR 2.00–2.06 (2.03, n = 2); mesothoracic TR 2.16–2.35 (2.26, n = 2); metathoracic TR 2.00–2.10 (2.05, n = 2). Wing ( Figure 7D ) length 3.02–3.10 (3.06, n = 2) mm, width 1.10–1.16 (1.13, n = 2) mm, costal ratio 0.74–0.77 (0.75, n = 2); membrane slightly infuscated, anterior veins dark brown; second radial cell 3.16–4.30 (4.03, n = 2) × longer than first; cubital fork originating at level of base of r-m cross vein; macrotrichia on costa, R 1, R 2, R 3, abundant on distal 1/3 of cell r 3 and m 1, sparse on cell m 2. Halter whitish.

Abdomen. Dark brown, with dense setae. Genitalia ( Figure 7H ): sternite 8 rounded; posteromedian excavation U-shaped; sternite 10 with 8 pairs of setae; cerci short; two ovoid spermathecae without necks, measuring 12.80–15.20 (14.00, n = 2) by 10.40–11.80 (11.1, n = 2) µm and 10.00–12.50 (11.20, n = 2) by 10.00–10.70 (10.30, n = 2) µm; plus a small third rudimentary spermatheca.

Distribution

Argentina (Neuquen, Río Negro), Chile (Llanquihue) ( Figure 19 ).

Type

Holotype male, Chile, Prov. Llanquihue, Ensenada , 14–15 December 1926, F. and M. Edwards ( BMNH).

Other specimens examined

Argentina: Neuquen prov., Villa La Angostura , 11–15 January 2004, G. Spinelli, 1 female, sweep net ; Río Negro prov., Challhuaco, 41°15 ′ 30 ″ S, 71°17 ′ 06 ″ W, 1326 m, 24 October to 28 February 2007, L. Hernández – F. Montes de Oca , 1 female, Malaise trap .

Discussion

This species is similar to S. (A.) bicinctipes by virtue of the leg coloration. Characters for distinguishing both species are in the key and in the discussion section of that species.

Remarks

This short description of the male of S. (A.) ornaticrus was made based on photographs from holotype deposited in BMNH. Measurements are not available.

This is the first description of the female of S. (A.) ornaticrus .

Figures

Figure 7. Stilobezzia (A.) ornaticrus Ingram and Macfie: (A–B) holotype male; (A) antennal flagellum; (B) genitalia (ventral view). (C–H) female; (C) head with detail of complete antennal flagellum; (D) wing; (E) thorax (lateral view); (F) hind femur and tibia; (G) hind tarsomeres; (H) genitalia. Scale bars 0.05 mm.

Figure 19. Distribution of Stilobezzia (A.) nigerrima, Stilobezzia (A.) ornaticrus and Stilobezzia (A.) tridentis.