Nostima velutina Edmiston & Mathis 2005

Nostima velutina

DIAGNOSIS.—Nostima velutina specimens are distinguished from congeners by the following combination of external characters: gena with dense microtomentum ventrally; velvety black microtomentum on scutum between dorsocentral setae and over entire scutellar disc, slightly less dense anteriorly; mesonotum striped laterally; wing crossveins paler than veins, white, at least anterior portion; and tergite 5 of male with silvery gray microtomentum along posteriomedial margin.

DESCRIPTION.—Small shore flies, body length 1.15–1.25 mm; pale to dark brown with silver, silvery gray, velvety black, velvety brown, yellowish silver, and golden microtomentum.

Head: Frons with velvety brown ventrolateral triangles, anterior semicircle brown with yellowish silver microtomentum. Occiput brown with yellowish silver microtomentum, laterally with silvery gray microtomentous stripes contiguous with silvery gray microtomentum on thorax. Outer vertical seta length of inner vertical seta; paravertical seta absent. Scape and pedicel yellowish brown; flagellomere 1 yellowish brown ventrally, brown dorsally. Facial background coloration yellowish brown with golden silvery microtomentum; narrow band of silvery gray microtomentum along eye margin beginning at vertical setae, extending and gradually blending with silvery gray microtomentum on gena. Medially along parafacial, a brown band extending lateroventrally below gena. Face yellowish brown with golden silvery microtomentum. Gena with dense, silvery gray microtomentum; postgena dorsally with dense, silvery gray microtomentum in band contiguous with band of silvery gray microtomentum laterally on thorax. Maxillary palpus yellowish brown; prementum yellowish brown.

Thorax (Figure 171): Scutal length 0.38–0.42 mm; scutellar length 0.18–0.19 mm. Mesonotum yellowish brown with yellowish silver microtomentum, darker along dorsocentral line, stripe of silvery gray microtomentum along interalar line; scutellum medially yellowish brown with yellowish silver microtomentum, darker laterally, with lateral silvery gray microtomentum contiguous with silvery gray microtomentum on mesonotum; anepisternum yellowish brown with sparse, yellowish silver microtomentum; katepisternum dorsally with silvery gray microtomentum, ventrally yellowish brown with sparse, yellowish silver microtomentum; subscutellum yellowish brown with sparse, yellowish silver microtomentum; anatergite yellowish brown with sparse, yellowish silver microtomentum. Chaetotaxy: anterior dorsocentral seta – length of posterior seta; anterior notopleural seta – length of posterior seta; lateral scutellar seta length of apical seta. Wing (Figure 171): length 1.08–1.30 mm; width 0.49–0.58 mm; costal-vein ratio 0.80–0.93; M-vein ratio 0.40–0.63; amber background with brown veins; crossveins r-m and dm-cu white and surrounded by white spot. Halter yellowish white. Legs pale yellowish brown with tarsomere 5 darker.

Abdomen (Figures 124–126, 243, 244): Tergites 1–5 shiny dark brown; tergite 4 with oval-shaped silvery gray microtomentose posterolateral spot; tergite 5 with small, silvery gray microtomentose patch on posteromedial margin. Male genitalia (Figures 124–126): epandrium-cerci-surstyli complex fused; epandrium U-shaped; cercus crescent-shaped with many setulae, fused ventrally with epandrium, separated dorsally from epandrium by narrow V-shaped groove; subepandrial plategonite-hypandrium fused; surstylus completely fused ventrally with epandrium and with many ventral setae; aedeagal apodeme triangular in lateral view with rounded anterior and posterior projections, lateral medial projections rounded; aedeagus rectangular with tip curved dorsally; subepandrial plate reduced to a broad rounded dorsal projection; gonite with broad base and prominent medioventral setulae; gonite with posterior undulate projection with spatulate tip; hypandrium broadly triangular in ventral view.

TYPE MATERIAL.—The holotype male of Nostima velutina is labeled “MEXICO, Chi[apa]s.San Cristobal de Las Casas 7087′[,] 18–19.V. 1969 [18–19 May 1969] B.V.Peterson/HOLOTYPE Nostima velutina Edmiston & Mathis CNC [red].” The holotype is glued on the right side of the head and thorax to a pin, is in good condition (thorax with small amount of dust; right wing torn posteriorly; left wing in an attached microvial), and is deposited in the CNC. One paratype (1; CNC) bears the same locality label data as the holotype.

DISTRIBUTION (Figure 127).—Neotropical: Mexico (Chiapas).

ETYMOLOGY.—The species epithet, velutina, is derived from the Latin adjective velutinus, meaning velvety. The name refers to the velvety appearance of the head and thorax.