Hydrochasma lineatum, Mathis, Wayne N. & Zatwarnicki, Tadeusz, 2013

Mathis, Wayne N. & Zatwarnicki, Tadeusz, 2013, A revision of the shore-fly genus Hydrochasma Hendel (Diptera, Ephydridae), ZooKeys 363, pp. 1-161 : 99-101

32. Hydrochasma lineatum sp. n. Figs 100, 180-183

Diagnosis.

This species is distinguished from other congeners by the following combination of characters: Small shore flies, body length 1.20-1.70 mm. Head: Antenna mostly dark gray; parafacial silvery white, concolorous with facial coloration; gena-to-eye ratio 0.18-0.19. Thorax: Wing with costal vein ratio 0.70-0.72; M vein ratio 0.53-0.56. Forecoxa mostly blackish gray to gray. Abdomen: Tergites 1-4 extensively brownish black to blackish gray dorsally, lacking lateral wedges. Male terminalia (Fig. 180-183): Combined structures generally elongate, in posterior view height nearly 4 × width, generally sparsely setulose, setulae especially sparse over midsection; epandrium with dorsal arch above cerci interrupted, not connected, in posterior view (Fig. 180) with basal third rectangular with angles rounded, apical 2/3 narrowed, linear, extended as abutting, narrow, almost parallel sided processes, apex tapered to a point, in lateral view (Fig. 181) generally elongate and narrow, ventral 2/3 essentially parallel sided, linear, apex rounded; cerci moderately short, height nearly twice width, semi-hemispherical (Fig. 180), fused ventrally to epandrium; aedeagus in lateral view (Fig. 183) generally very elongate and narrow, narrowly tubular, length over 10 × width, mostly parallel sided, in ventral view (Fig. 182) elongate, narrow, tubular, parallel sided, apex rounded; phallapodeme in lateral view (Fig. 183) narrowly elongate, moderately and conspicuously expanded toward anterior margin, keel as a irregularly tapered extension, in ventral view (Fig. 182) clavate with gradually widened basal portion and anterior apex narrowly T-shaped; gonite in lateral view (Fig. 183) narrowly elongate, bar-like, very shallowly arched, in ventral view (Fig. 182) narrowly elongate, very shallowly sinuous; hypandrium in lateral view (Fig. 183) elongate, very shallow, nearly flat and parallel sided, in ventral view (Fig. 182) moderately deeply V-shaped, with anterior portion moderately robustly developed, tapered toward anterior, rounded apex, posterior margin deeply V-shaped.

Type material.

The holotype male of Hydrochasma lineatum is labeled "TRINIDAD. St. Georg.: Filette (1 km SE, 10°47'N, 61°21'W), YarraRiver, 25 June 1993,Wayne N.Mathis/USNM ENT 00117969 [plastic bar code label]/HOLOTYPE ♂ Hydrochasma lineatum Mathis & Zatwarnicki, USNM [red]." The holotype is double mounted (minuten in a block of plastic), is in excellent condition, and is deposited in the USNM. Seven paratypes (4♂, 3; USNM) bear the same label data as the holotype.

Type locality.

Trinidad and Tobago. Trinidad. St. George: Filette (1 km SE; 10°47'N, 61°21'W).

Other specimens examined.

Neotropical. TRINIDAD and TABAGO. Tobago. St. John: Bloody Bay River (11°18'N, 60°38'W), 14 Jun 1993, W. N. Mathis (1♂; USNM); Charlotteville (5 km S; Hermitage River and beach; 11°18.9'N, 60°34.2'W), 11 Jun 1993, W. N. Mathis (2♀; USNM); Hermitage (11°18.9'N, 60°34.5'W), 22 Apr 1994, D. and W. N. Mathis (1♂; USNM). St. Paul: Argyle Falls (11°15'N, 60°35'W), 21 Apr 1994, W. N. Mathis (1♂; USNM).

Distribution

(Fig. 100). Neotropical: Trinidad and Tobago (Tobago, Trinidad).

Etymology.

The species epithet, lineatum, is of Latin derivation and mean linear, referring to the straight, line-like shape of the epandrium in posterior and lateral views.

Remarks.

This species is distinguished from congeners of the leucoproctum group by the very elongated ventral epandrial processes that are mostly parallel-sided, although tapered subapically to the apex. In addition, the hypandrium is uniquely shaped, being elongated, slender, and with an elongated anterior base that is almost twice the length of the depth of the posteromedial, hypandrial emargination.