TRABAJOS CIENTÍFICOS

A new species of the genus Stilobezzia from the Nahuel Huapi National Park, Argentina (Diptera: Ceratopogonidae)

Una nueva especie del género Stilobezzia del Parque Nacional Nahuel Huapi, Argentina (Diptera: Ceratopogonidae)

Cazorla, Carla G. and Gustavo R. Spinelli

División Entomología, Museo de La Plata, Paseo del Bosque s/n, 1900 La Plata, e-mail: (CGC) carlacazorla@fcnym.unlp.edu.ar, (GRS) spinelli@fcnym.unlp.edu.ar

Recibido: 1-II-2012;
Aceptado: 4-VI-2012

ABSTRACT. A new species, Stilobezzia ( Acanthohelea) longisternalis, collected in the Nothofagus forest of the Nahuel Huapi National Park (Argentina) is described, photographed and illustrated based on the examination of male and female adults. The new species can be easily recognized by the elongate and narrow posteromedian projection of the male sternite 9; it is compared with S. (A.) hirsuta Ingram & Macfie.

KEY WORDS. Stilobezzia (Acanthohelea); New species; Nothofagus forest; Argentina.

RESUMEN. Una nueva especie, Stilobezzia (Acanthohelea) longisternalis, colectada en los bosques de Nothofagus del Parque Nacional Nahuel Huapi (Argentina), se describe, fotografía e ilustra en base al estudio de machos y hembras adultos. La nueva especie se reconoce fácilmente por presentar una proyección posteromediana alargada y delgada en el esternito 9 de los machos. Se compara con S. (A.) hirsuta Ingram & Macfie.

PALABRAS CLAVE. Stilobezzia (Acanthohelea); Nueva especie; Bosques de Nothofagus; Argentina.

INTRODUCTION

The predaceous midge genus Stilobezzia Kieffer is a large and diverse genus of Ceratopogonidae, worldwide in distribution. The adult females are important predators on other small insects, and the immature stages are found in a wide variety of aquatic and semiaquatic habitats, including streams, lakes and ponds margins, puddles, swamps, rice fields, rock pools, and tree holes (De Meillon & Wirth, 1991; Cazorla et al., 2006).
Ingram & Macfie (1931) described 10 new species of Stilobezzia from Argentinean and Chilean northern Patagonia that are placed in the subgenus Acanthohelea Kieffer (Wirth & Grogan, 1988), which is represented in the Neotropical region by 27 species (Cazorla & Spinelli, 2012). The purpose of this paper is to describe a new species of Stilobezzia (Acanthohelea) recently collected in the Nothofagus forest of the Nahuel Huapi National Park.

MATERIAL AND METHODS

Specimens were collected with Malaise traps, preserved in 70ºethanol and subsequently slide mounted in Canada balsam, then examined, measured and drawn with a binocular compound microscope with an attached camera lucida. Terminology follows the Manual of Central American Diptera (Brown et al., 2009). Photomicrographs were taken with a digital camera Micrometrics SE Premiun, through Nikon Eclipse E200 microscope. Types of the new species are deposited in the collection of the División Entomología, Museo de La Plata, Argentina (MLP).

RESULTS

Stilobezzia (Acanthohelea) longisternalis
Cazorla & Spinelli sp. nov (Figs. 1-9)

Figs. 1-9. Stilobezzia (Acanthohelea) longisternalis Cazorla & Spinelli, n. sp. 1-5, male; 6-9, female; 1, 6, head; 2, 7, wing; 3, genitalia; 4, genitalia (parameres removed); 5, parameres; 8, thorax; 9, abdominal segments 8-10. (Scale bars = 0.05 mm).

Diagnosis. Only species of Stilobezzia (Acanthohelea) from Patagonia with the male sternite 9 bearing an elongate and narrow posteromedian projection. Females with 14 strong and 13 thinner scutellar setae and abdominal segment 8 heavily sclerotized.
Description. Male adult. Head (Fig. 1) dark brown. Antennal flagellomeres brown; plume dark brown, dense; antennal ratio 0.98-1.18 (1.08, n= 8). Palpus dark brown; third segment cylindrical with subapical sensory pit; fifth segment as long as third; palpal ratio 3.71-4.29 (4.18, n= 8). Thorax: scutum yellowish brown except anterior, posterior margins, sublateral anterior areas dark brown; scutellum yellowish with 17-18 stout setae, 12 thinner ones; pleura yellowish brown; postscutellum dark brown. Legs yellowish brown, hairy; hind coxa brown; first tarsomere of hind leg with basal stout spine; prothoracic TR 1.72-2.00 (1.88, n= 8); mesothoracic TR 1.94-2.11 (2.00, n= 7); metathoracic TR 1.67-1.81 (1.73, n= 8). Wing (Fig. 2) length 2.58-2.83 (2.70, n= 8) mm; width 0.80-0.88 (0.83, n= 8) mm; membrane slightly infuscated; second radial cell 3.50-4.62 (3.81, n= 8) times longer than first; cubital fork at level of beginning of r-m crossvein; macrotrichia on costa, R₁, R₂, R₃, distal ¼ of m₁, sparce on r₃. Halter pale. Abdomen dark brown. Genitalia (Figs. 3-5): dark brown; tergite 9 not produced beyond apex of gonocoxite, lateral margins of proximal 1/2 straight, slightly divergent, lateral margins of distal 1/2 convergent, posterior margin rounded; sternite 9 with conspicuous, elongate, narrow posteromedian projection extending to gonocoxite midlength; sternite 10 slightly visible, spiculate, produced beyond base of cerci; cercus slender, divergent. Gonocoxite stout, 1.72 times longer than greatest breadth, inner margin with pointed protuberance at distal 1/3. Gonostylus yellowish brown distally, slightly shorter than gonocoxite, almost straight, tip blunt. Parameres separated, subparallel, short; each with basal apodeme at level of gonocoxite midlength; proximal portion slender, distal portion broader, rounded. Aedeagus represented by 2 stout, slightly sinuose, convergent sclerites, each with basal tip curved laterad, distal tip curved, pointed.
Female adult. As for male, with following differences. Head (Fig. 6) brown. Antennal flagellomeres dark brown; antennal ratio 1.42. Palpus dark brown; palpal ratio 3.87. Mandible with 7 teeth. Thorax (Fig. 8): scutellum with 14 stout setae, 13 thinner ones; hind tibial comb with 9 spines; claws shorter than fifth tarsomere; prothoracic TR 2.06; mesothoracic TR1.89; metathoracic TR 1.75. Wing (Fig. 7) length 2.76 mm; width 0.98 mm; membrane slightly infuscated; second radial cell 4.30 times longer than first; cubital fork slightly anterior to level of beginning of r-m crossvein; macrotrichia on costa, R₁, R₂, R₃, M₁, M₂, abundant on r₃, sparce on m₁. Abdomen brown, segment 8 heavily sclerotized. Genitalia (Fig. 9): anterior margin of sternite 8 slightly concave, posteromedian excavation V-shaped; sternite 10 elongate, with 7-8 pairs of setae; cercus short; two ovoid spermathecae, measuring 14 µ by 7.4 µ and 10.3 by 8.5 µ; necks minute, almost indistinguishable.
Types. Holotype male, allotype female: Argentina, Río Negro prov., Nahuel Huapi National Park, AºÑireco (Complejo Challhuaco), 41º11' 51.9''S 71º19' 40''W, 962 m, 20-XII-2006/ 23-I-2007, Masaferro, Garre & Montes de Oca, Malaise trap (MLP). Other paratypes, 11 males, as follows: same data as holotype, 8 males (MLP); Argentina, Río Negro prov., Nahuel Huapi National Park, Mallín de los Patos, 41º15' 48.6''S 71º17' 50.3'' W, 1020 m; XII-2006/ 23-I-2007, Garre & Montes de Oca, 3 males, Malaise trap (MLP).
Distribution. Argentina (Río Negro province).
Derivation of specific epithet.
A reference to the particular elongate posteromedian projection of the male sternite 9.

DISCUSSION

Stilobezzia (Acanthohelea) longisternalis can be easily recognized by the conspicuous and narrow posteromedian projection of the male sternite 9. Another patagonian species, S. (A.) hirsuta Ingram & Macfie, also has the male sternite 9 bearing a posteromedian projection, but in this case the projection is shorter, broader and hyaline. Moreover, S. (A.) hirsuta lacks a basal spine in the first tarsomere of the hind leg, and the posterior margin of the male tergite 9 is bilobed.

ACKNOWLEDGEMENTS

This study was supported by the Darwin Initiative project "Capacity building for biodiversity studies of freshwater insects in Argentina".

LITERATURED CITED

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