Planinasus shannoni (Malloch)

Mathis, Wayne N., Rung, Alessandra & Kotrba, Marion, 2012, A revision of the genus Planinasus Cresson (Diptera, Periscelididae), ZooKeys 225, pp. 1-83 : 30-33

6. Planinasus shannoni (Malloch) Figures 535-38

Schizochaeta shannoni Malloch 1934: 53.

Planinasus shannoni . Hennig 1969: 614 [generic combination]. Mathis and Rung 2011: 363 [world catalog].

Description of male.

Moderately small flies, body length 2.35-2.55 mm.

Head: Frons mostly bare of microtomentum, shiny, except for densely microtomentose, velvety-appearing, anterolateral angles, blackish brown; frons much wider than long, frontal ratio averaging 0.42; interfrontal seta long, length subequal to that of lateral vertical seta. Scape and pedicel blackish brown except for whitish yellow, ventral projection of pedicel; pedicel with ventral projection long, about 1/2 length of basal flagellomere; basal flagellomere long, slightly more than twice basal width, yellowish; arista bearing 13-14 dorsal rays, 3-4 ventral rays. Face very wide (at least of male), facial ratio 0.67; dorsal 2/3 (above transverse carina) wide, shield-like, medial portion (between antennal bases) moderately densely microtomentose, mostly whitish but with blackish brown background coloration also appearing, lateral portion (just below antennae) bare, shiny, especially ventrally, and with ventral margin of antennal grooves quite evident; ventral 1/3 of face (below transverse facial carina) mostly densely microtomentose, somewhat shiny, whitish to whitish yellow, with blackish, somewhat bare, narrowly triangular area extended obliquely medioventrally from ventral margin of antennal groove; large facial setae 3, not arranged in transverse rows, becoming smaller ventrally; largest facial seta inserted dorsolaterally, dorsoclinate and convergent; 2nd largest seta inserted medioventrally from largest seta, porrect and parallel; 3rd seta inserted ventrolaterally and with porrect to slightly ventroclinate orientation. Clypeus and palpus blackish brown. Gena concolorous with ventral 1/3 of face.

Thorax: Generally dark colored, black to blackish brown, anepimeron paler, brownish, with ventral margin yellowish; mesonotum thinly invested with microtomentum, appearing subshiny, with slightly metallic brown luster medially, becoming more steel blue laterally; postpronotum dark brown; area from postpronotum and extended through notopleuron mostly bare, shiny; anepisternum thinly invested with microtomentum, mostly appearing dull, grayish brown; other pleurites less densely invested. Wing conspicuously and uniformly infumate, brownish, base slightly paler, more hyaline. Coxae yellowish; forefemur mostly blackish, only basal 1/8 yellowish, also with a preapical, yellowish annulus; middle and hind femora mostly yellowish, apical 1/4-1/3 dark brown; tibiae blackish brown; tarsi, except apical 1-2 dark brown tarsomeres, yellowish. Forefemur with posteroventral surface bearing 1 large seta at apical 1/3.

Abdomen: Uniformly blackish brown to black, mostly shiny, very sparsely invested with microtomentum. Male abdomen: Tergites 1+2-6 well developed, lengths of tergites 3-6 subequal; tergite 7 narrow; sternites 3, 4, 5 generally as rectangular plates, slightly wider than long, lateral margins shallowly arched; no sternites 6, 7, neither segment forming an annulus. Male terminalia (Figs 35-38): Epandrium in lateral view (Fig. 35) higher than wide, more or less triangular but with dorsal surface truncate, short, anterior margin nearly straight, posterior margin nearly straight dorsally, ventral portion arched; surstylus length less than 1/3 length of epandrium, extended from ventroposterior margin of epandrium in nearly oblique alignment with epandrium, in lateral view (Fig. 35) short, widely truncate apically, bearing 1 large, basal setula; hypandrium in ventral view (Fig. 36) broadly U-shaped, robustly developed anteriorly, arms tapered, more slender than wide base, anterior margin rounded; pregonite in ventral view (Fig. 36) approximately triangular to subrectangular, with anterior and lateral margins receded and slightly round corners; postgonite in ventral view (Fig. 36) convoluted, bearing a ventral digitiform lobe with approximately 3 setulae; phallus in ventral view (Fig. 38) complex, partially sclerotized; phallapodeme elongate, in lateral view (Fig. 38) parallel sided, tubular, nearly straight, truncate apically, in ventral view (Fig. 36) slightly tapered, apex narrowly developed; ejaculatory apodeme in lateral view (Fig. 37) almost as long as ½ length of phallapodeme, apex only slightly expanded.

Description of female. Same as male except as follows: Head: Frontal ratio 0.55; face and antenna entirely blackish brown; face not as wide, facial ratio 0.32; face projected forward on ventral 1/2, bulbous, evenly arched transversely, shallowly arched vertically, mostly flat.

Thorax: Forefemur lacking preapical annulus.

Type material. The holotype male is labeled "IquitosPeru MarApr1931 RCShannon/Type No. 49549 U.S.N.M. [red, number handwritten]/Schizochaeta shannoni Type det. JRMALLOCH [species name and “Type” handwritten, label has a black sub- border]." The holotype is double mounted (glued to a paper point), is in fair condition (the middle and hind right legs are missing), and is deposited in the USNM (49549). The allotype female and four additional paratypes, all males, bear the same locality, date, and collector data as the holotype. In the original description, Malloch stated that a paratype would be deposited in the British Museum (Natural History).

Type locality. Peru. Loreto: Iquitos (03°45'S, 73°16.3'W).

Other specimens examined.ECUADOR. Orellana: Rio Tiputini Biodiversity Station (0°38.2'S, 76°8.9'W), 12-26 Aug 1999, A. Baptista, M. Kotrba, W. N. Mathis (2♂; USNM, ZSMC).

Distribution (Fig. 5). Neotropical: Ecuador (Orellana), Peru (Loreto).

Etymology. Malloch named this species after his friend and fellow dipterist, Raymond Corbett Shannon, who was the collector of the type series. R. C. Shannon conducted much field work in the Neotropical Region and most of his collections were donated to the USNM.

Remarks. This species is very similar to Planinasus venezuelensis but is distinguished from it by the mostly yellow mid- and hindfemora, which have at most the apical one-fourth to one-third dark, and the shape of the surstylus (Fig. 35) short and widely truncate apically. The surstylus of Planinasus venezuelensis is long, J-shaped. From other congeners, this species is distinguished by the following characters of males: the pale-colored basal flagellomere and apex of the ventral projection of the pedicel, the whitish microtomentum on the mid-dorsal surface of the face, the relatively approximate antennal bases, and the narrowly triangular areas that extend medioventrally from the ventral margin of the antennal groove. The shape of structures of the male terminalia also clearly distinguishes this species (see Figs 35-38).