Forcipomyia (Trichohelea) limnetis Ingram and Macfie, 1931

Marino, Pablo I. & Spinelli, Gustavo R., 2004, Descriptions of the Patagonian species of the subgenus Trichohelea of Forcipomyia, with a key to the Neotropical species (Diptera: Ceratopogonidae), Journal of Natural History 38 (17), pp. 2251-2262 : 2254-2257

Forcipomyia (Trichohelea) limnetis Ingram and Macfie, 1931

( figures 1–9 )

Forcipomyia (Apelma) limnetis Ingram and Macfie, 1931: 169 (male; Argentina).

Forcipomyia (Trichohelea) limnetis: Wirth, 1974: 12 (in catalogue to Neotropical species; subgeneric position); Spinelli and Wirth, 1993: 27 (in list of Argentinean species); Borkent and Wirth, 1997: 49 (in catalogue to world species); Borkent and Spinelli, 2000: 23 (in catalogue to Neotropical species).

Forcipomyia limnetis: Spinelli, 1998: 325 (in list of Argentinean species).

Lasiohelea shannoni Ingram and Macfie, 1931: 171 ( Lasiohelea ; female; Argentina). New synonymy.

Forcipomyia (Trichohelea) shannoni: Wirth, 1974: 12 (in catalogue to Neotropical species; comb.); Spinelli and Wirth, 1993: 27 (in list of Argentinean species); Borkent and Wirth, 1997: 50 (in catalogue to World species); Borkent and Spinelli, 2000: 23 (in catalogue to Neotropical species).

Forcipomyia shannoni: Spinelli, 1998: 325 (in list of Argentinean species).

Diagnosis

A medium-sized, brown species; flagellomeres 1–8 distinctly broader than long; third segment of maxillary palpi swollen, sensory pit deep opening by a small pore; CR 0.55; tarsal claws equal, small, bifid at extreme apex; female genital sclerotization open, subquadrangular; two pyriform spermathecae; aedeagus stout, basal arch extending to half of total length; parameres inverted U-shaped, lateral arms strongly divergent.

Female

Wing. Length 1.23 mm (1.08–1.34, N ~4); breadth 0.56 mm (0.50–0.60, N ~4).

Head. Dark brown. Vertex pilose. Eyes bare, contiguous by a distance equal to diameter of three ommatidia. Flagellum of antenna ( figure 1 ) with flagellomeres 1–8 distinctly broader than long; 9–12 elongated, cylindrical, approximately 2.3 times longer than greatest breadth; distal flagellomere slightly longer than 9–12; AR 1.69 (1.54–1.82, N ~4). Palpus ( figure 2 ) with third segment nearly as long as the combined length of fourth and fifth segments, with deep sensory pit opening by a small rounded pore; PR 1.91 (1.75–2.06, N ~4). Mandible ( figure 3 ) abruptly tapering to pointed apex, armed with 10 very small teeth. Maxilla ( figure 4 ) straight, tapering to pointed tip, with six pairs of minute teeth.

Thorax. Scutum dark brown, with narrow pale longitudinal admedian stripes, prescutellar area paler; scutellum pale brown, with approximately 20 strong setae and 15 slender ones. Legs brown, densely covered by hairs; prothoracic TR 2.02 (1.93–2.07, N ~4), mesothoracic TR 1.98 (1.93–2.00, N ~4), metathoracic TR 2.02 (1.92–2.12, N ~4). Claws ( figure 5 ) short, stout and curved, bifid at extreme apex; empodium well developed. Wing ( figure 6 ) densely covered with dark macrotrichia, more abundant on anterior margin; a small pale area situated immediately distad to the second radial cell; first radial cell almost obliterated, second radial cell well developed; CR 0.55 (0.52–0.57, N ~4). Halter whitish.

Abdomen. Pale brown. Genital sclerotization ( figure 7 ) open, subquadrangular. Two well-sclerotized, pyriform spermathecae ( figure 8 ), subequal, measuring 0.056× 0.046 mm and 0.050× 0.042 mm, necks 0.004 mm.

Male

Similar to female with the usual sexual differences. Hind tarsal ratio 1.70.

Genitalia. Sternite 9 aproximately half as long as broad, with broad caudomedian excavation; tergite 9 short, with conspicuous, hairy apicolateral processes; sternite 10 spiculate anteriorly. Gonocoxite narrow, three times longer than broad; gonostylus nearly straight, slender, as long as gonocoxite. Aedeagus ( figure 9 ) triangular, stout with rounded blunt tip; basal arms slender, strongly sclerotized; basal arch extending to half of total length; distal portion lightly sclerotized. Parameres highly sclerotized, inverted U-shaped, lateral arms strongly divergent.

Distribution

In subantarctic forest of northern Patagonia (Neuquen and Río Negro provinces in Argentina, Osorno in Chile) ( figure 24 ).

Types

Holotype „ of Forcipomyia limnetis (slide in Canada balsam), holotype ” of Lasiohelea shannoni (pinned), Argentina, Río Negro Prov., Lake Correntoso , 18–25 November 1926, F. and M. Edwards. In the Natural History Museum, London (both examined during the present study).

Other specimens examined

Argentina, Río Negro Prov., Lake Correntoso , 1”, 18–25 November 1926, F. and M. Edwards (paratype of L. shannoni , slide in Canada balsam in the Natural History Museum, London) ; Neuquen Prov. Stream Pedregoso and provincial route No. 67 (5 km W of El Portezuelo), 3 February 1986, G. Spinelli, 1”; Río Negro Prov., ‘Nahuel Huapi’ National Park, Stream Chall-Huaco, 26 January 1988, G. Spinelli, 1”; ‘ Nahuel Huapi’ National Park, Lake Guillelmo , 24 February 1994, G. Spinelli, 1 ”. Chile, Osorno, Pucatrihue , 1 December 1992, G. Spinelli, 1” .

Discussion

The study of the types of Lasiohelea shannoni (female) and Forcipomyia limnetis (male), both with identical collecting data, reveals that their differences obey two usual sexual differences within species of the subgenus Forcipomyia (Trichohelea) , representing thus, the two sexes of a single species.

The original description and illustrations of F. limnetis are very accurate except for the aedeagus, which shows lower basal arch and broader apex. Ingram and Macfie (1931) report a metathoracic TR ‘about 2.4’ for L. shannoni . Perhaps they measured this feature from the slide-mounted paratype, which shows the second

tarsomere of the hind leg somewhat folded, being the measure most probably overestimated. On the other hand, the pinned holotype is in excellent condition, and shows a metathoracic TR only slightly longer than 2.00.

Females of this species are barely distinguishable from those of F. (T.) tehuelche sp. n. The males, however, differ by the following genital characters: caudomedian excavation of sternite 9 broad (narrow in tehuelche ), aedeagus with basal arch extending to one-half of total length and without distal process (extending to onetenth of total length, with a distinctive distal process in tehuelche ), and lateral arms of parameres strongly divergent (subparallel in tehuelche ).

Figures

FIGS 1–9. Forcipomyia limnetis Ingram and Macfie. (1–8) Female. (9) Male. (1) Flagellum. (2) Maxillary palpus. (3) Mandible. (4) Maxilla. (5) Fourth and fifth tarsomeres and claws. (6) Wing. (7) Genital sclerotization. (8) Spermathecae. (9) Aedeagus. Scales: 0.05 mm.

FIG. 24. Known localities for the Patagonian species of the subgenus Trichohelea.