Hydrochasma falcatum, 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 : 41-43

14. Hydrochasma falcatum sp. n. Figs 80-85

Diagnosis.

This species is distinguished from congeners by the following combination of characters: Small to moderately small shore flies, body length 1.25-2.10 mm. Head: Antenna mostly dark gray; parafacial silvery white, concolorous with facial coloration; gena-to-eye ratio 0.20-0.22. Thorax: Wing with costal vein ratio 0.83-0.85; M vein ratio 0.53-0.54. Forecoxa silvery white; forefemur lacking a distinctive, comb-like row of stout setulae along anteroventral surface; tibiae mostly gray; hindtibia bearing an ventroapical, spur-like seta. Abdomen: Tergites 3-4 with distinctive, deep, gray wedge-like marking along lateral margin of darkened, dorsal coloration; tergite 5 of male gray with posteromedial area darkened. Male terminalia (Figs 81-84): Epandrium generally elongate, setulae moderately sparse, on medial portion, in posterior view (Fig. 81) with dorsal arch attenuate, not connected, dorsal 2/3-3/4 somewhat diamond shaped, widest just ventrad of cerci, thereafter ventrally tapered to arrow-shaped apex, arrow-shaped apex with width subequal to length, apex with narrowly incised medially, in lateral view (Fig. 82) narrowly elongate, mostly parallel sided, anterior margin shallowly sinuous, apex somewhat bluntly rounded; cerci short, length in lateral view (Fig. 82) slightly more than twice width, hemispherical; aedeagus in lateral view (Fig. 84) relatively simple, narrowly tubular, length 5 × width, in ventral view (Fig. 83) also tubular, narrow, elongate; phallapodeme in lateral view (Fig. 84) linear, very shallowly curved, extended keel narrow and short, as a slight bump, in ventral view (Fig. 83) narrowly Y-shaped with apical arms short and with short, subapical crossbar; gonite in lateral view (Fig. 84) narrowly elongate, bar-like, more curved than phallapodeme, in ventral view (Fig. 83) narrowly bar-like, elongate, nearly straight; hypandrium in lateral view (Fig. 84) elongate, length about 2/3 that of aedeagus, straight, rod-like, slightly expanded on apical half, in ventral view (Fig. 83) with anterior margin broadly truncate, lateral margins nearly parallel sided, posterior margin deeply incised with bifurcate, short, processes sublaterally.

Type material.

The holotype male of Hydrochasma falcatum is labeled "PERU. Madre de Dios: Manu, Erika (near Salvación; 12°47[six, 50.7]'S, 71°13[six, 23.3]'W; 550 m), 5-6 Sep 1988, W. N. Mathis/USNM ENT 00285976 [plastic bar code label]/HOLOTYPE ♂ Hydrochasma falcatum 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. Twenty-six paratypes (19♂, 7♀; USNM) bear the same label data as the holotype. Other paratypes are as follows: PERU. Madre de Dios: Quebrada Romero (near; Rio Manu; 12°07'S, 70°58'W), 8 Sep 1988, W. N. Mathis (1♂, 2♀; USNM); Río Manu, Cocha Salvador (11°59.9'S, 71°13.9'W 300m), 14 Sep 1988, W. N. Mathis (3♂, 10♀; USNM).

Type locality.

Peru. Madre de Dios: Río Manu, Erika (near Salvación; 12°50.7'S, 71°23.3'W; 550 m).

Other specimens examined.

Neotropical. BOLIVIA. La Paz: Guanay (15°29.8'S, 67°52.7'W), 460 m), 13 Mar 2001, W. N. Mathis (3♂, 3♀; USNM); Guanay (3 km E; 15°30.2'S, 67°52.3'W; 500 m), 14 Mar 2001, W. N. Mathis (1♂; USNM); Puente Villa (17 km W; 16°20.9'S, 67°49'W; 2070 m), 11 Mar 2001, W. N. Mathis (1♂, 1♀; USNM); San Pedro (3 km NE; 16°S, 67°35.3'W; 780 m), 12 Mar 2001, W. N. Mathis (12♂, 4♀; USNM).

BRAZIL. Amazonas: Igarapé Cabeça Branca (ca. 40 km N Manaus; 02°35.1'S, 60°01.9'W; 65 m), 8 May 2010, D. and W. N. Mathis (3♂; USNM).

ECUADOR. Loja: Loja: Catamayo (03°59'S, 79°21'W), Dec 1955, R. Levi-Castillo (1♂; USNM).

HONDURAS. Cortés: San Pedro Sula (8 km S; 15°25.7'N, 88°01.4'W), 25-26 Sep 1995, D. and W. N. Mathis (1♂; USNM).

MEXICO. Chiapas: Cascadas de Agua Azul (17°15.3'N, 92°06.9'W), 7 May 1985, W. N. Mathis (1♂, 1♀; USNM). Veracruz-Llave: Fortin de las Flores (18°54'N, 97°W; 952 m), 2 May 1985, W. N. Mathis (4♂, 6♀; USNM).

TRINIDAD and TOBAGO. Tobago. St. John: Parlatuvier (creek; 11°17.9'N, 60°35'W), 14 Jun 1993, W. N. Mathis (1♂; USNM).

Distribution

(Fig. 85). Neotropical: Bolivia (La Paz), Brazil (Amazonas), Ecuador (Loja), Honduras ( Cortés), Mexico (Chiapas, Veracruz-Llave), Peru (Madre de Dios), Trinidad and Tobago.

Etymology.

The species epithet, falcatum, is of Latin derivation and means sickle shaped, referring to the sickle-shaped gonite in lateral view.

Remarks.

Like Hydrochasma glochium and to a lesser degree like Hydrochasma urnulum , this species has an expanded apical portion of the extended epandrial process (best seen in posterior view). That process, however, has only moderate, lateral extensions (Fig. 81). The hypandrium of Hydrochasma falcatum is somewhat rectangular in ventral view with a distinct, V-shaped posteromedial emargination (Fig. 83). In males of Hydrochasma glochium , the expanded apical portion is more pronounced (Fig. 86), and the hypandrium in robustly V-shaped (Fig. 88). This species is also like those of the faciale group in having a spur-like seta ventroapically on the hindtibiae.