Sesommata trachyptera

Sesommata trachyptera

ADULT (Figures 399, 400).—Length of forewing: , 5.7–6.3 mm; , 6–7 mm. A moderately small species with dark fuscous forewings in the male and an elongate patch of rough, semi-erect, slender sex scales along the base of Cu; forewings of female paler, more brown, and irrorated with scattered white scales.

Head: Vestiture fuscous in male, pale buff in female; often with white piliform scales arising on lower frons near inner rim of eye. Antennae approximately 0.5–0.6 the length of forewing, 38–42–segmented; scape fuscous (in male) to light brown (female) dorsally, white ventrally; pecten consisting of 6–9 dark hairs; flagellum fuscous to brown dorsally, banded with buff; white to pale buff ventrally. Maxillary palpi white to cream. Labial palpi mostly dull white, with lateral ventral surfaces of apical segment fuscous; second segment with 10–13 dark hairs arising laterally.

Thorax: Pronotum dark fuscous to brown. Venter white to cream. Forewings dark fuscous in male, rarely with scattered white scales over distal third; an elongate patch of rough, semi-erect and relatively slender sex scales along base of Cu, ventral surface without specialized sex scales; forewings of female generally lighter, more brown with a rather heavy irroration of white and black scales over distal third; two cream-white costal spots sometimes present beyond middle; fringe fuscous in male, brown streaked with white in female. Hind wings dark fuscous in male, paler fuscous in female. Costal hair pencil absent. Forelegs fuscous dorsally and ventrally, except for cream-white ventral surfaces of femur; tarsal banding indistinct, buff. Midlegs light fuscous to brown with more white ventrally; tarsal banding more distinct. Hind legs light brown dorsally, cream white ventrally.

Abdomen: Dark fuscous to brown dorsally; nearly so in male ventrally but mostly cream in female ventrally. Male without lateral sex scales.

Male Genitalia: As shown in Figures 443–446). Uncus bilobed; lobes broadly conical, widely separated. Gnathos a relatively large, median lobe bearing a single small spine. Valvae slender, terminating in a complex, irregularly trilobed apex, as in S. leuroptera. Anellus highly asymmetrical, with a broad lobe bearing a dense cluster of apical spines arising from left side; spine patch more sinuate than in S. leuroptera; aedoeagus with apex broad and flat, nearly truncate; a large spine cluster arising dorsally near middle.

Female Genitalia: As shown in Figure 558. Apex of ovipositor broad, approximately 0.9 mm wide. Colliculum with thickened, folded walls densely covered internally with placoid spicules. Corpus bursae more lightly covered with smaller, more slender spicules; a single spinose signum present midway along bursa. Spermatheca greatly lengthened, approximately twice the length of bursa copulatrix; ductus spermathecae tightly coiled; utriculus more spherical in outline, without spicules; a relatively large lateral lagena arising near posterior end.

IMMATURE STAGES.—Unknown.

HOLOTYPE.—. Esquel, Lago Menéndez, Sagrario Puerto, 550 m, Chubut Province, Argentina, 21 Feb 1979, E.S. Nielsen (ZMUC).

PARATYPES.—ARGENTINA. Chubut Prov.: Esquel, Lago Menéndez, El Sagrario Puerto, 550 m, 9, 21 Feb 1979, E.S. Nielsen. Rio Negro Prov.: Lago Nahuel Huapi, Puerto Blest, 770 m, 1, 3–8 Dec 1981, Nielsen & Karsholt; 6, 28 Feb 1979, E.S. Nielsen. San Carlos de Bariloche, Colonia Suiza, 800 m, 1, 22–23 Nov 1981; 2, 24 Nov 1981; 1, 2 Dec 1981; 2, 3 Dec 1981; 2, 23 Dec 1981; 1, 5–7 Jan 1982, Nielsen & Karsholt; same locality, 810 m, 5, 1, 15 Jan 1979, E.S. Nielsen.

CHILE. Cautin Prov.: Fundo Chacamo, 600–700 m, 35 km NW of Neuva Imperial, 5, 18, 17–23 Feb 1981, L. Peña. Ñuble Prov.: Las Trancas, 1300 m, 21 km E of Recinto, 1, 17 Jan 1979, D. & M. Davis & B. Akerbergs, malaise-trap; 1, 2 Mar 1968, Flint & Peña.

Paratypes in ANIC, BMNH, MACN, MHNS, USNM, and ZMUC.

HOST.—Unknown.

FLIGHT PERIOD.—22 November to 2 March; univoltine?

DISTRIBUTION (Map 3).—This species occurs in the temperate Valdivian forest region of southern Argentina and Chile. In Argentina it has been found from Lago Nahuel Huapi south to Lago Menéndez. In Chile it was encountered at two localities near Volcan Chillan in Ñuble Province and farther south in the coastal range in Cautin Province.

ETYMOLOGY.—The species name is derived from the Greek trachys (rough) plus pteron (wing, feather), in reference to the presence of roughened sex scales near the base of the male forewing.