Hydrochasma crenulum, 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 : 11-12

2. Hydrochasma crenulum sp. n. Figs 6-10

Diagnosis.

This species is distinguished from congeners by the following combination of characters: Small shore flies, body length 1.25-1.90 mm. Head: Subglobose generally, very broad ventrally, oral opening comparatively large. Antenna mostly dark gray; at least pedicel black. Parafacial silvery white, concolorous with facial coloration; gena-to-eye ratio 0.21-0.24. Thorax: Mesonotum yellowish to golden brown; pleural area gray. Wing with costal vein ratio 0.93-0.96; M vein ratio 0.44-0.46. Forefemur bearing a distinctive, comb-like row of stout setulae along anteroventral surface; tibiae mostly gray; hindtibia bearing a long, spur-like seta ventroapically. Abdomen: Tergites broadly darker gray medially, becoming lighter gray laterally but unevenly, lacking wedge-shaped gray to silvery gray areas or a sharply contrasted demarcation between dorsal and lateral coloration; tergite 5 of male gray. Male terminalia (Figs 7-10): Combined structures generally moderately elongate, in posterior view height not quite twice width; epandrium with dorsal arch interrupted medially, not connected above cerci; generally sparsely setulose; in posterior view (Fig. 7) as an inverted, divergent U on dorsal third, medial portion with lateral margins angled medially, robustly developed, ventral apical portion somewhat rectangular, lateral margins (height less than that of cerci) parallel sided, partially bifurcate, narrowly and deeply incised medially, broadly truncate apically, in lateral view (Fig. 8) widely notched and with a robust, curved, partially hook-like ventral process; cerci moderately long, height about 1.5 × width (Fig. 7), tenuously attached ventrolaterally with epandrium; aedeagus in lateral view (Fig. 10) moderately elongate, about 2.5 × longer than greatest width, tubular, slightly wider basally and more so apically, with apical portion unevenly rounded, in ventral view (Fig. 9) moderately wide basally, thereafter tapered medially but just before apex, apex distinctly but narrowly extended laterally; phallapodeme in lateral view (Fig. 10) broad and short with width subequal to length, keel wide and long, extended margin irregularly rounded, in ventral view (Fig. 9) narrowly T-shaped with arms short and right angled; gonite in lateral view (Fig. 10) narrow, moderately elongate, bar-like, slightly arched, in ventral view (Fig. 9) more conspicuously curved; hypandrium in lateral view (Fig. 10) elongate, shallow, anterior 1/3 obtusely angled, parallel sided, in ventral view (Fig. 9) with posterior third divergently U-shaped, anterior portion slightly narrower, plate-like, anterior margin broadly rounded.

Type material.

The holotype male of Hydrochasma crenulum is labeled "PERU. Cuzco: Pau-cartambo, Atalaya,R[ ío]. AltoMadredeDios,600m,4Sep1988,WNMathis/USNM ENT 00092795 [plastic bar code label]/HOLOTYPE ♂ Hydrochasma crenulum 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. Fifty paratypes (34♂, 16♀; USNM) bear the same label data as the holotype.

Type locality.

Peru. Cuzco: Paucartambo, Atalaya ( Río Alto Madre de Dios; 12°53.3'S, 71°21.6'W; 600 m).

Other specimens examined.

Neotropical. PERU. Madre de Dios: Diamante ( Río Alto Madre de Dios; 12°19.9'S, 70°57.5'W; 400 m), 7 Sep 1988, W. N. Mathis (4♂, 10♀; USNM); Río Manu, Erika (near Salvación; 12°50.7'S, 71°23.3'W; 550 m), 5-6 Sep 1988, W. N. Mathis (4♂, 2♀; USNM).

Distribution

(Fig. 6). Neotropical: Peru (Cuzco, Madre de Dios).

Etymology.

The species epithet, crenulum, is of Latin derivation and means notched, referring to the conspicuous notch in the epandrium that is best seen in lateral view.

Remarks.

The shapes of structures of the male terminalia of Hydrochasma crenulum are unmistakable and readily distinguish this species from congeners, especially those of the faciale group. This is especially evident in the ventral portion of the epandrium in lateral view that is generally robustly developed, is conspicuously and widely notched, and terminates as an extended, curved process.