Hydrochasma williamsae, 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 : 31-33

10. Hydrochasma williamsae sp. n. Figs 1, 11, 57-61

Diagnosis.

This species is distinguished from congeners by the following combination of characters: Small to moderately small shore flies, body length 1.50-2.30 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 facial coloration; parafacial silvery white, concolorous with face; mesonotum yellowish to golden brown; gena-to-eye ratio 0.25-0.27. Thorax: Pleural area gray (Fig. 1). Wing with costal vein ratio 0.63-0.65; M vein ratio 0.52-0.53. 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 (Fig. 11). Abdomen: Tergites 1-4 with broad, medial brown stripe, uneven lateral margin, lacking wedge-shaped, gray to silvery gray areas laterally (Fig. 1); tergite 5 of male truncate apically, mostly gray with faint brown, medial stripe. Male terminalia (Figs 57-60): Combined structures generally moderately elongate and appearing angulate, in posterior view height about 1.3 × width, generally setulose, especially medially at midlength but also along ventral margins; epandrium with dorsal arch above cerci attenuated, not connected, in posterior view (Fig. 57) with cercal cavity forming a broad U, with arms of U robustly developed, ventral portion of arms with each lateral half robustly developed, tapered to dorsal apex, apex pointed medially, dorsal portion of epandrium squarish, especially prominent dorsolateral, rounded angles; ventral portion of epandrium ventrad of midlength, shallow, V-shaped notch, as 2 robust, ventral projections that are tapered to a narrow point ventroapically, forming a deeply and narrowly incised medial incision or narrowly U-shaped pocket, in lateral view (Fig. 58) with very irregular anterior and posterior margins, generally robust, apex narrowly pointed; cerci moderately long, height more than twice width, widely semi-hemispherical (Fig. 57), pointed dorsally, in lateral view (Fig. 58) evenly lunate, not attached lateroventrally or ventrally with epandrium; aedeagus in lateral view (Fig. 60) elongate, length slightly more than 3.5 × width, tubular, shallowly curved, especially apically, apex narrowly pointed, in ventral view (Fig. 59) elongate, widest sub-basally, thereafter apically tapered to narrowly truncate apex; phallapodeme in lateral view (Fig. 60) irregularly triangular, short, with extended, medial keel short and narrow, not skewed, apex of keel rounded, in ventral view (Fig. 59) a slightly elongate, moderately robust T with keel portion as a symmetrical, lateral bulge; gonite in lateral view (Fig. 60) moderately narrow, moderately elongate, bar-like, nearly straight, end toward aedeagus tapered to point, in ventral view (Fig. 59) small, width only slightly longer than length, tapered medially; hypandrium in lateral view (Fig. 60) like a deep, globularly rounded pocket, wide, tapered to point posteriorly, anterior margin broadly rounded, in ventral view (Fig. 59) very broadly and robustly developed, width only slightly longer than length, posterior margin very shallowly emarginated, anterior margin broadly rounded.

Type material.

The holotype male of Hydrochasma williamsae is labeled "BELIZE. Stann Cr[ee]k. Dist[rict]. MullinsRiver[,] (17km N Dangriga)[,] 29 March 1988, Wayne N. Mathis/HOLOTYPE ♂ Hydrochasma williamsae Mathis & Zatwarnicki, USNM [red]/USNM ENT 00094378 [plastic bar code label]." The holotype is double mounted (minuten in a block of plastic), is in excellent condition, and is deposited in the USNM. Sixteen paratypes (5♂, 11♀; USNM) bear the same label data as the holotype.

Type locality.

Belize. Stann Creek: Mullins River (17 km N Dangriga; 17°06.2'N, 88°17.8'W).

Other specimens examined.

Nearctic: UNITED STATES. NEW MEXICO. Grant: Mimbres River (32°43.8'N, 107°52'W; 1665 m), 13-22 Aug 2007, 2009, D. and W. N. Mathis, T. Zatwarnicki (2♂; USNM).

TEXAS. Llano: Enchanted Rock (30°30.4'N, 98°49.1'W), 15 Jun 1953, W. W. Wirth (1♂; USNM).

Neotropical. COSTA RICA. Cartago: La Suiza (09°51.5'N, 83°37.5'W), 28 Jun 2001, W. N. Mathis (2♂, 4♀; USNM). Limón: Talamanca ( Estación Gandoca; 9°37.4'N, 82°41.7'W), 18 May 2004, W. Porras (1♂; INBIO).

HONDURAS. Cortés: Omoa (16°47.8'N, 87°58.4'W), 26 Sep 1995, D. and W. N. Mathis (1♂, 1♀; USNM).

Distribution

(Fig. 61). Nearctic: United States (New Mexico, Texas). Neotropical: Belize (Stann Creek), Costa Rica (Cartago, Limón), Honduras ( Cortés).

Etymology.

The specific epithet, williamsae, is a genitive patronym to honor our colleague and cherished friend, the late Ms Hollis Barton Williams, who provided technical support to us for nearly 35 years. Holly passed away August 23, 2009.

Remarks.

This species, as noted previously in the “Remarks” section of Hydrochasma faciale , is distinguished by structures of the male terminalia, especially the generally short and robust epandrium in posterior and lateral views. The more angulate dorsolateral shoulders (best seen in posterior view) and the tapered and pointed ventral epandrial process are unique to this species and distinguish it from congeners.