Hydrochasma castilloi, 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 : 10-11

1. Hydrochasma castilloi sp. n. Figs 2-6

Diagnosis.

This species is distinguished from congeners by the following combination of characters: Small shore flies, body length 1.60-1.90 mm. Head: Subglobose, very broad ventrally, oral opening comparatively large. Antennal coloration variable, entirely yellow to nearly evenly divided between yellowish and dark gray, dorsal and anterior surfaces of pedicel and basal flagellomere extensively dark gray. Parafacial silvery white, concolorous with face; gena-to-eye ratio 0.20-0.23. Thorax: mesonotum yellowish to golden brown; pleural area gray. Wing with costal vein ratio 0.72-0.81; M vein ratio 0.43-0.44. Forefemur bearing a distinctive, comb-like row of stout setulae along anteroventral and posteroventral surfaces; tibiae mostly gray; hindtibia bearing a large, spur-like seta ventroapically. Abdomen: Tergites 1-4 with dorsum mostly grayish brown, with lateral margin unevenly demarcated from silvery gray to gray portion, lacking grayish wedges laterally on tergites 2-4; tergite 5 light gray to silvery gray, similar to coloration along lateral margins of preceding tergites but with posterior margin blackish brown to slate black, similar to coloration of medial area on tergites 1-4; medial coloration on tergites 1-4 wide, occupying most of dorsum, dark, grayish to slate black. Male terminalia (Figs 2-5): Combined structures generally moderately elongate, in posterior view (Fig. 2) height less than twice width, generally setulose; epandrium with dorsal arch above cerci narrowly developed, completely connected, in posterior view (Fig. 2) as an inverted, rounded U on dorsal half, ventral half more narrowly developed than dorsal portion, lateral margins shallowly curved medially, deeply bifurcate medially, medial bifurcation as wide as ventral epandrial arm, narrowly pointed apically, bearing longer setulae along dorsal arch and at midheight, in lateral view (Fig. 3) narrowly rectangular on dorsal 1/4, nearly vertical, thereafter ventrally oriented anteroventrally, more thickly developed, apical 1/3 tapered to narrowly rounded apex; cerci moderately long, height about 2.5 × width, semi-hemispherical (Fig. 2), not attached lateroventrally with epandrium; aedeagus in lateral view (Fig. 5) elongate, parallel sided, about 8 × longer than width, tubular, shallowly sinuous, with apical portion moderately pointed, in ventral view (Fig. 4) mostly parallel sided on basal 2/3 except for immediate base that is tapered medially, apical 1/3 abruptly narrowed, slightly spatulate, apex narrow, rounded; phallapodeme in lateral view (Fig. 5) somewhat narrow, moderately elongate, unevenly bar-like with medial margin shallowly arched, keel skewed toward attachment with hypandrium, narrow but extended, extended margin roundly rectangular, in ventral view (Fig. 4) broadly as a short T with arms short and triangular; gonite in lateral view (Fig. 5) narrow, elongate, bar-like, shallowly sinuous, in ventral view (Fig. 4) very shallowly curved; hypandrium in lateral view (Fig. 5) elongate, shallow, tapered at both apices, more narrowly so posteriorly, in ventral view (Fig. 4) with posterior half to 2/3 spindle shaped, becoming wider with short extended lateral processes just before posterior margin, posterior margin shallowly emarginated, anterior portion as an arrowhead with posteriorly directed robust extensions and with lateral and anterior margins shallowly arched, roundly pointed.

Type material.

The holotype male of Hydrochasma castilloi is labeled "Ecuador[.]Loja Catamayo Dec. 1955/Collr.Levi-Castillo/USNM ENT 00118297 [plastic bar code label]/HOLOTYPE ♂ Hydrochasma castilloi Mathis & Zatwarnicki, USNM [red]." The holotype is double mounted (glued to a paper triangle)), is in excellent condition, and is deposited in the USNM. Sixteen paratypes (11♂, 9♀; USNM) bear the same label data as the holotype.

Type locality.

Ecuador. Loja: Catamayo (03°59'S, 79°21'W), Dec 1955.

Other specimens examined.

ECUADOR. El Oro: Puerto Bolivar (03°16'S, 79°60'W), Dec 1955, R. Levi-Castillo (1♂, 2♀; USNM). Guayas: Cone (02°10.1'S, 79°38'W), Jun 1955, R. Levi-Castillo (1♀; USNM).

Distribution

(Fig. 6). Neotropical: Ecuador (El Oro, Guayas, Loja).

Etymology.

The specific epithet, castilloi, is a genitive patronym to honor Roberto Levi-Castillo, the collector of the type series and many other shore flies from Ecuador.

Remarks.

This species has been frequently misidentified as Hydrochasma patens in collections. Our study of the holotype of Hydrochasma patens , however, reveals it to be a separate and distinct, although closely related species. Fortunately, the structures of the male terminalia are very diagnostic and distinctive. These structures in Hydrochasma castilloi are generally much more robust and shorter in both posterior and lateral views (Figs 2-5). In addition, the aedeagus in lateral view (Fig. 5) is shallowly sinuous, and the hypandrium in ventral view (Fig. 4) has much shorter, posterolateral processes. In Hydrochasma patens , the aedeagus in lateral view is shallowly arched, not sinuous, and the posterolateral hypandrial processes are three to four times longer than those of Hydrochasma castilloi . In general form, structures of the male terminalia of this species are more similar to those of Hydrochasma faciale and Hydrochasma williamsae , being relatively short and robustly developed. The dorsum of the epandrium in Hydrochasma castilloi is complete though thinly developed; whereas in Hydrochasma faciale and Hydrochasma williamsae , the dorsal band is incomplete resulting in an open dorsal margin to the cercal cavity.