Tachytrechus dios Brooks

Brooks, Scott E. & Cumming, Jeffrey M., 2008, The Tachytrechus alatus species group (= Syntomoneurum Becker) revisited: new species and revised species group limits (Diptera: Dolichopodidae), Zootaxa 1676, pp. 1-27 : 11-14

Tachytrechus dios Brooks sp. nov.

(Figs. 5, 13)

Diagnosis. Male. One notopleural bristle; M with pronounced S-shaped bend; R4+5 and M subparallel distally (Fig. 5A); wing lacking costal swelling; fore tarsus with tarsomeres 4 and 5 enlarged (Fig. 5B); hind femur mainly or entirely pale; right and left basiventral epandrial lobes relatively short, asymmetrical with right lobe more developed; apicoventral epandrial lobe elongate, projected ventrally (Figs. 5C, 5D); cercus subrectangular (Fig. 5D); hypandrium with lamellate process subapically and on left lateral margin, elongate sickle-like projection near middle on right side (Figs. 5C, 5E).

Description. Male: Body length: 5.0 mm, wing length: 5.1 mm. Head: Vertex distinctly excavated, vertical bristle weak and short, less than half as long as paravertical bristle, subequal to upper postocular seta, pair of strong ocellar bristles, pair of strong paravertical bristles. Postoculars mainly white, becoming stronger ventrally, upper 4–5 postoculars black, short. Frons blackish with metallic blue reflections. Face broad, narrowest at middle. Face and upper part of clypeus dark metallic greenish-brown, margin and lower part of clypeus golden yellow, clypeus rounded below. Palpus white with pale hairs and a distinct black apical seta. Antenna: Scape subtriangular in lateral view, laterally compressed, dark brown dorsally, yellowish ventrally, about 0.5x as long as pedicel and postpedicel combined; pedicel yellowish; postpedicel yellow basally, blackish on apical 2/3 on lateral surface, more extensively blackish on medial surface, ovoid with narrowed apex, about 1.7x as long as wide; arista-like stylus subapical, black, white at extreme tip, about 3x as long as postpedicel, basal article about 0.1x as long as distal article. Thorax: Notum metallic green with coppery reflections, with black medial vitta with metallic blue margin, silvery pruinosity anteriorly and laterally; acrostichals biserial, 6 dorsocentrals, 1 presutural, 1 sutural, 2 supraalars, 1 postalar, 1 posthumeral, 1 postpronotal, 1 notopleural bristle (see Remarks). Scutellum metallic green with strong inner bristle and weak outer seta. Pleuron with silvery pruinosity, metaepisternum with 1–2 weak hairs. Legs: Fore coxa yellow, mid and hind coxae brownish with silvery pruinosity; femora mainly yellow, posterodorsal surface of fore and mid femur dark with metallic reflections; tibiae yellow; tarsi yellowish basally, becoming brownish from apical portion of tarsomere 2 onwards, tarsomeres 4–5 modified (see below). Foreleg: Coxa with pale pile and weak setae, apical margin with 2 strong outer and several weak inner setae; femur with distinct tubercle behind basal cluster of 2 strong bristles, posterior preapical seta present; tibia with 3 dorsal setae, 2 posteriors and 2 apicals; tarsus longer than tibia, tarsomeres 4–5 enlarged (Fig. 5B), tarsomere 4 and base of 5 pale, distal portion of tarsomere 5 dark brown, tarsomere ratio: 2.5/1.9/1.8/1.0/1.0. Midleg: Femur with distinct tubercle on ventral surface proximal to mid-length, 1 strong anterior preapical bristle, 1 distinct posteroventral preapical seta; tibia with 4 anterodorsal setae, 1 posterodorsal in basal portion, 2 dorsals, 2–3 ventrals, 4 strong apicals; tarsus 1.5x longer than tibia, tarsomere ratio: 6.0/6.5/2.5/1.0/1.3. Hindleg: Femur with 1 strong anterodorsal preapical bristle; tibia with 3 anterodorsal setae, 3 posterodorsals, 1 preapical dorsal, 2 apicals, with dentiform posteroapical process; tarsus about 1.4x longer than tibia, with hook-shaped posterobasal process opposite weak apical dentiform process of tibia, tarsomere ratio: 4.3/7.6/3.0/1.0/1.2. Wing (Fig. 5A): Veins dark brown, membrane with gray tinge; costa unmodified, without swelling; M with two strong obtuse bends in distal half; R4+5 and M parallel distally; crossvein dm-cu at midpoint of wing, longer than distal section of CuA1. Calypter with black setae. Abdomen: Tergites 1–5 metallic green with coppery reflections, with silvery pruinosity laterally, posterior margin of tergites coppery; tergite 5 with large posterior membranous region, extended laterally towards ventral margin of sclerite; sternite 5 with eversible glandular structure (retracted in holotype); tergite 6 and segment 7 coppery brown with silvery pruinosity; sternite 8 silvery pruinose with a few long setae near posterior margin. Hypopygium (Figs. 5C, 5D): Epandrium brownish-metallic green; left basiventral epandrial lobe short, pointed apically, seta present adjacent to base of lobe, right basiventral epandrial lobe larger, projected medially, tapered towards apex, apex slightly expanded and hooked, seta present near middle of lobe; apicoventral epandrial lobe elongate, projected ventrally, laterally flattened, with pair of pale setae, right lobe longer than left lobe; accessory epandrial process absent. Surstylus: Ventral lobe digitiform, flattened dorsoventrally, with ridged ventral surface, apex with blunt curved seta; dorsal lobe about half as long as ventral lobe, flared apically, apex with several setae laterally and rugose membraneous portion medially. Apicolateral arm of postgonite with medial process present, with hook-like process apically. Cercus (Fig. 5D) subrectangular in dorsal view, pale yellow with apical and lateral margin black, lateral margin with long setae. Hypandrium (Fig. 5E) narrowed apically, with subapical lamellate process on right lateral margin, with lamellate process along left lateral margin, and with elongate lateroventral sickle-like projection near middle on right side. Phallus simple, tubular in distal part, with fin-like dorsal projection in middle section (Fig. 5C).

Female: Unknown.

Type material. Holotype ɗ, PERU: Madre de Dios , Avispas, 10–20.ix. 1962, 400 m, L. Peña ( CNC).

FIGURE 5. Tachytrechus dios Brooks sp. nov.: (A) male wing; (B) apical part of male foretarsus; (C) hypopygium (left lateral view); (D) cercus (dorsal view); (E) hypopygium ventral view (postgonite, surstylus and cerci not shown). Abbreviations: A1: anal vein; apv lobe: apicoventral epandrial lobe; bv lobe: basiventral epandrial lobe; cerc: cercus; CuA1: 1st anterior branch of cubital vein; dm-cu: discal medial-cubital crossvein; epand: epandrium; hypd: hypandrium; M: medial vein; pgt: postgonite; ph: phallus; R1: 1st radial vein; R2+3: 2nd + 3rd radial vein; R4+5: 4th + 5th radial vein; vsur: ventral lobe of surstylus.

Distribution. ( Fig. 13 ). Tachytrechus dios is known only from the type locality of Avispas, Peru. Etymology. The new species name is derived from Madre de Dios , the Peruvian Department of the type locality.

Remarks. Most of the thoracic bristles of the unique male holotype are missing. As such, chaetotaxy was assessed based on the setal sockets.

Figures

FIGURE 13. Known distribution of Tachytrechus alatus (Becker), T. analis (Parent), T. dios Brooks sp. nov., T. giganteus (Brooks) and T. peruicus Yang & Zhang.