A review of the species of Rhynchopsilopa Hendel from China (Diptera, Ephydridae)

Abstract Species of the shore-fly genus Rhynchopsilopa Hendel from China are reviewed. Four new species (Rhynchopsilopa guangdongensis sp. n., Rhynchopsilopa huangkengensis sp. n., Rhynchopsilopa jinxiuensis sp. n., Rhynchopsilopa shixingensis sp. n.) and two previously known species, Rhynchopsilopa longicornis (Okada) and Rhynchopsilopa magnicornis Hendel, are described or redescribed. A key to the species hitherto known from China is presented.


Introduction
Among shore flies, Rhynchopsilopa is apparently unique in having an association with ants (Farquharson 1921, Wirth 1968, Freidberg and Mathis 1985. Freidberg and Mathis (1985) demonstrated through choice experiments that this association, which may be obligate, is specific to workers of the genus Crematogaster Lund, with no apparent association with other ant genera. Crematogaster is an abundant, ecologically diverse genus of ants that is found worldwide and is easily recognized by its unusual, heartshaped gaster. The adult flies are proctophiles on workers of Crematogaster and feed by injecting digestive liquids through the anus and into the abdomen of the ant prey. The fly then ingests the resultant slurry of partially digested liquids from the ant's abdomen. We know nothing about the immature stages of Rhynchopsilopa, nor has a biological association with Crematogaster been documented for most of the species.
The unique and somewhat bizarre biology of Rhynchopsilopa is not the only feature that makes Rhynchopsilopa appealing to research. Adults of Rhynchopsilopa are relatively attractive in having a shiny habitus that is metallic dark blue to black in luster and color. Despite their striking appearance and exhibiting a unique biology, the basic systematics of the genus remains fragmentary and incomplete, with many undescribed species, especially from the Afrotropical Region (Freidberg personal communication).
The genus Rhynchopsilopa Hendel 1913 is one of 11 genera in the tribe Psilopini (subfamily Discomyzinae) and currently includes 20 species (Mathis and Zatwarnicki 1995). The genus is distinctive and is easily recognized by the long, pendant antennae; the short frons; the depressed face with a sharp epistoma; the long proboscis, and the convex thorax and abdomen (Wirth 1968). Rhynchopsilopa is only known from the Old World, and the Afrotropical Region has greatest species diversity, with 14 described species. One species, R. nitidissima Hendel, is known from the Palearctic Region, and five have been recorded from the Oriental Region. Of the five Oriental species, only two have been recorded from China (Cogan andWirth 1977, Mathis andZatwarnicki 1995): Rhynchopsilopa longicornis (Okada) and R. magnicornis Hendel. The purpose of this paper is to redescribe the species of Rhynchopsilopa that are known from China, and to describe four additional species as new to science. A key to the Chinese species is also provided.

Material and methods
The descriptive terminology, with the exceptions noted in Mathis (1986) and Mathis and Zatwarnicki (1990a), follows that published in the Manual of Nearctic Diptera (McAlpine 1981). Because specimens are small, less than 2.50 mm in length, study and illustration of the male terminalia require use of a compound microscope. For most of the structures of the male terminalia, we follow the terminology that other workers in Ephydridae have used (see references in Mathis 1986and Mathis and Zatwarnicki 1990a, 1990b. The species descriptions are composite and not based solely on holotypes.

Two venational indices used in the descriptions are defined below
Costal vein index is the straight line distance between the apices of R 1 and R 2+3 (costal section II) divided by the distance between the apices of R 2+3 and R 4+5 (costal section III). M vein ratio is the straight line distance apicad of crossvein dm-cu divided by the distance along M between crossvein dm-cu and r-m.
Thorax generally convex, dark blue to black, with microtomentum sparse to lacking; supra-alar seta absent; prescutellar acrostichal seta well developed; only posteriormost dorsocentral seta well developed; scutellum conspicuously wider than long, posterior margin broadly rounded, disc sparsely setulose; basal scutellar seta at most about 1/2 length or less than apical seta; anepisternum with 2 large setae. Wing mostly hyaline; crossveins not darkened; vein R 2+3 usually extended to costal margin, lacking stump vein; R stem vein bare of setulae dorsally. Knob of haltere yellow to tan. Legs yellow to dark brown; forebasitarsus yellow to tan, only apical 1-2 tarsomeres dark brown.
Abdomen generally convex, bare of microtomentum, shiny, blackish; tergites 3-4 long, 5th tergite very short and lacking prominent, dorsally erect setae along posterior margin. Male terminalia: epandrium in posterior view as an inverted, rounded U (open ventrally), in lateral view generally elongate, usually thin to very thin, often slightly wider subventrally; cercus in posterior view thinly lunate to hemispherical; presurstylus, if present, short, no more than ½ length of postsurstylus, tapered to point ventroapically, apex bearing setulae, often greatly reduced or lacking; postsurstylus longer than wide, tapered to a ventral point, often with sinuous or curved margins; subepandrial plate usually bar-like, attenuate medially; pregonite bearing short setulae; aedeagus longer than wide, with sclerotized portion deeply bifurcate, appearing as 2 ventral extensions; phallapodeme long and narrow, in lateral view with a rod-like keel; hypandrium in lateral view moderately deep, pocket-like, or very shallow, nearly flat. Head subshiny, brownish red. Setulae and setae of head black; lateral vt as long as medial vt; 1 pair of strong oc; 1 pair of strong proclinate orb. Face subshiny, reddish orange; epistoma yellow; palpus brown. Gena with 1 strong seta. Arista with 8 dorsal rays.

Key to species of Rhynchopsilopa from China
Thorax subshiny, brown, with violet reflections; mesonotum dark brown, with short and sparse setulae; anepisternum and katepisternum brownish yellow. Thoracic setulae and setae black. 1 pair of posts dc, sutural dc absent; 2 rows of acr weak and short; posterior npl as long as anterior npl; anepisternum with 2 setae, length of ventral seta 2× that of dorsal seta; katepisternal seta weaker than ventral anepisternal seta; 1 weak sa, 1 strong ia; scutellum with 2 pairs of sc, apical sc stronger than lateral sc. Forecoxa yellowish, mid and hind coxae brownish yellow; femora yellow; tibiae and tarsomeres 1-4 yellowish, tarsomere 5 dark (  Distribution. China (Guangdong, Guangxi). Etymology. The species epithet is derived from the type locality, Guangdong.
Remarks. This new species is similar to R. pallipes Wirth but may be distinguished from the latter by the reddish orange face, the costal vein index (0.45), the M vein index (2.1), and by the darkened 5th tarsomere. In R. pallipes, the face is yellow, the costal vein index is 0.59, the M vein index is 2.1, and all tarsi are yellow (Wirth 1968 Diagnosis. Body shiny black, with some bluish reflections. Face black, with blue reflections; palpus brownish yellow, moderate at apex; arista with 7-8 dorsal rays. 1 pair of posts dc, sutural dc absent. Forecoxa brown at extreme base, yellow at apex, mid and hind coxae brown; femora dark brown; tibiae and tarsomeres 1-4 yellowish, tarsomere 5 brown. Forefemur with rows of pd and pv, each about as long as width of forefemur; mid femur with a row of av, which are shorter than width of mid femur. Mesonotum and abdomen with short and sparse setulae. Costal vein index 0.43, M vein index 2.0; first costal section of male not thickened. Male genitalia: epandrium very thin, only slightly expanded ventrally; hypandrium in ventral view hourglass-like, with rounded anterior margin, in lateral view shallow to nearly flat; postsurstylus wide at base and slender at apex in lateral view; gonite/subepandrial plate slender, sinuous; phallapodeme with long, extended keel.
Description. Male body length: 1.9-2.1 mm; wing length: 2.4-2.6 mm. Head shiny black, with blue reflections. Setulae and setae of head black. Lateral vt as long as medial vt; 1 pair of strong oc; 1 pair of proclinate orb. Face black, with blue reflections; epistoma brownish yellow; palpus brownish yellow, moderate at apex. Gena with 1 strong seta. Arista with 7-8 dorsal rays. Thorax shiny black, with blue reflections; mesonotum with short and sparse setulae. Thoracic setulae and setae black. 1 pair of posts dc, sutural dc absent; 2 rows of weak, short acr, posterior npl as long as anterior npl; katepisternal seta weaker than anepisternal seta; 1 weak sa, 1 strong ia; scutellum with 2 pairs of sc, apical sc stronger than lateral sc. Forecoxa brown at extreme base, yellow at apex, mid and hind coxae brown; femora dark brown; tibiae and tarsomeres 1-4 yellow, tarsomere 5 brown . Forefemur with rows of pd and pv, each nearly as long as width of forefemur; mid femur with a row of av, which are shorter than width of mid femur. Costal vein index 0.43, M vein index 2.0; first costal section of male not thickened. Wing brownish yellow, veins brown. Haltere white.
Remarks. This new species is similar to R. magnicornis Hendel, but may be distinguished from the latter by the following characters: palpus brownish, forecoxa with a brown base, costal vein index 0.43, M vein index 2.0, and costal section I of the male not thickened. In R. fuscipennis Wirth, the palpus is yellowish, the forecoxa is yellowish, the costal vein index is 0.50, the M vein index is 2.2; and the costal section I of the male is thickened (Wirth 1968 Diagnosis. Body shiny black, with blue reflections. Face white; palpus white, stout at apex; arista with ten dorsal rays. 1 pair of posts dc, sutural dc absent. Forecoxa yellowish, mid and hind coxae brownish yellow; femora dark brown; tibiae and tarsomeres 1-4 yellowish, tarsomere 5 dark. Forefemur with strong pd and pv, each long, about twice width of forefemur; mid femur with a row of strong av. Mesonotum and abdomen with long and numerous setulae. Costal vein index 0.30, M vein index 2.0. Male genitalia: epandrium moderately wide, especially subventrally; hypandrium in ventral view anchor-like, in lateral view with narrow base and expanded anterior extension; postsurstylus with ventral half bearing a long, narrow process extended from anteroventral angle of basal portion, forming a long, curved anterior margin; gonite thick at base and slender at apex in ventral view; phallapodeme with arched base, extended keel narrow, elongate, width of keel somewhat uniform.
Description. Male body length: 2.1-2.4 mm; wing length: 2.8-3.0 mm. Head shiny black, with blue reflections. Setulae and setae of head black. Lateral vt as long as medial vt; 1 pair of strong oc; 1 pair of lateroclinate orb. Face, epistoma, and palpus white, the latter stout at apex. Gena with 1 strong seta. Arista with 10 dorsal rays.
Thorax shiny black, with blue reflections; mesonotum with long and numerous setulae. Thoracic setulae and setae black. 1 pair of posts dc, sutural dc absent; 2 rows of long and numerous acr; posterior npl as long as anterior npl; katepisternal seta weaker than anepisternal seta; 1 weak sa, 1 strong ia; scutellum with 2 pairs of sc, apical sc stronger than lateral sc. Forecoxa yellowish, mid and hind coxae brownish yellow; femora dark brown; tibiae and tarsomeres 1-4 yellowish, tarsomere 5 dark (Figs 17-19). Forefemur with strong pd and pv, each long, about 2× width of forefemur; mid femur with a row of strong av. Costal vein index 0.30, M vein index 2.0. Wing brownish yellow, veins brown. Haltere white.
Remarks. This new species is similar to R. fuscipennis Wirth, from which it may be distinguished by having 10 dorsal aristal rays, costal vein index of 0.30, and M vein index of 2.0. In R. fuscipennis Wirth, the arista has 7 dorsal rays, the costal vein index is 0.50, and the M vein index is 1.8 (Wirth 1968 Diagnosis. Face shiny black, with blue reflections; palpus yellow; epistoma brownish yellow; arista with 9 dorsal rays. 1 pair of posts dc, sutural dc absent. Forecoxa brown at extreme base, mid and hind coxae brown; forefemur yellow, mid and hind femora dark brown at base; tibiae and tarsomeres 1-4 yellowish, tarsomere 5 dark. Forefemur with pd and pv, about as long as width of forefemur; mid femur with a row of av. Mesonotum and abdomen with short and sparse setulae. Costal vein index 0.50, M vein index 2.2. Male genitalia: epandrium narrow; hypandrium in ventral view hourglasslike, with anterior margin shallowly rounded, in lateral view shallow to nearly flat; postsurstylus tapered toward apex in lateral view; gonite/subepandrial plate slightly thick; phallapodeme with process at middle in lateral view. Description. Male body length: 1.8-2.0 mm; wing length: 2.1-2.4 mm. Head shiny black, with blue reflections. Setulae and setae of head black. Lateral vt as long as medial vt; 1 pair of strong oc; 1 pair of proclinate orb. Face shiny black, with blue reflections; palpus yellow, stout at apex; epistoma brownish yellow. Gena with 1 strong seta. Arista with 9 dorsal rays.
Thorax shiny black, with blue reflections; mesonotum with short and sparse setulae. Thoracic setulae and setae black. 1 pair of posts dc, sutural dc absent; 2 rows of weak and short acr; posterior npl as long as anterior npl; anepisternum with 2 strong setae; 1 strong katepisternal seta, weaker than anepisternal seta; 1 weak sa, 1 strong ia seta; scutellum with 2 pairs of sc, apical sc stronger than lateral sc. Forecoxa yellow, with brown extreme base, mid and hind coxae brown; forefemur yellow, mid and hind femora dark brown, with yellow apex; tibiae and tarsomeres 1-4 yellowish, tarsomere 5 dark (Figs 25-27  Lateral vt as long as medial vt; 1 pair of strong oc; 1 pair of proclinate orb. Face and palpus yellow, the latter stout at apex; epistoma yellow. Gena with 1 strong seta. Arista with 8-9 dorsal rays.

Rhynchopsilopa magnicornis
Thorax shiny black, with blue reflections; mesonotum with long and numerous setulae. Thoracic setulae and setae black. 1 pair of posts dc, sutural dc absent; 2 rows of acr long and numerous; posterior npl as long as anterior npl; katepisternal seta weaker than anepisternal seta; 1 weak sa, 1 strong ia; scutellum with 2 pairs of sc, apical sc stronger than lateral sc. Forecoxa yellowish, mid and hind coxae brownish yellow; femora dark brown; tibiae and tarsomeres 1-4 yellowish, tarsomere 5 dark (Figs 33-35). Forefemur with strong pv, about two times longer than width of forefemur; mid femur with a row of strong av. Costal vein index 0.33, M vein index 2.2. Wing brownish yellow, veins brown. Haltere yellow.
Abdomen shiny black, with blue reflections. Abdomen with long and numerous setulae. Male genitalia (Figs 36-39): epandrium in lateral view (Fig. 37) slightly wide, bearing long setae on ventral 2/3 along posterior margin; cercus in posterior view (Fig. 36) narrowly hemispherical; presurstylus greatly reduced; postsurstylus in posterior view (Fig. 36) robust, broader basally, thereafter unevenly tapered to pointed apex, medial margin deeply sinuous, in lateral view ( Fig. 37) with basal half roughly triangular, slightly tapered ventrally, ventral half bearing a long, narrow process extended from anteroventral angle of basal portion, forming a long, slightly curved process from ventroanterior margin of basal portion, with a posterior knob at juncture of basal and ventral portions along porterior margin; aedeagus in posterior view (Figs 36, 39) narrowly elongate, more so than postsurstylus, ventrally extended process nearly straight; phallapodeme in lateral view (Fig. 37) transversely elongate with long extended, more or less evenly thick keel; subepandrial plate in ventral view (Fig. 38) subquadrangular; hypandrium in ventral view (Fig. 38) hourglass-like, with anterior margin broadly rounded, in lateral view (Fig. 37)  Diagnosis. Body shiny black, with blue reflections. Face reddish brown; palpus yellow, not stout at apex; arista with 8-9 dorsal rays. 1 pair of posts dc, sutural dc absent. Forecoxa yellow, with brown extreme base, mid and hind coxae brownish yellow; femora and tibiae yellow; foretarsomere 5 brown, mid and hind tarsomeres 4 and 5 brown, other yellow. Forefemur with rows of strong pd and pv, longer than width of forefemur. Mesonotum and abdomen with short and sparse setulae. Costal vein index 0.45, M vein index 2.3. Male genitalia: epandrium narrow; hypandrium large, round in ventral view; postsurstylus broadened at apex, but pointed at extreme apex, gonite/ subepandrial plate slender at base; phallapodeme with process at base in lateral view.
Description. Male body length: 1.9-2.1 mm; wing length: 2.4-2.6 mm. Head shiny black, with blue reflections. Setulae and setae of head black. Lateral vt as long as medial vt; 1 pair of strong oc; 1 pair of proclinate orb. Face reddish brown; epistoma and palpus yellow, the latter stout at apex. Gena with 1 strong seta. Arista with 8-9 dorsal rays.
Thorax shiny black, with blue reflections; mesonotum with short and sparse setulae. Thoracic setulae and setae black. 1 pair of posts dc, sutural dc absent; 2 rows of weak and short acr, posterior npl as long as anterior npl; katepisternal seta weaker than anepisternal seta; 1 weak sa, 1 strong ia; scutellum with 2 pairs of sc, apical sc stronger than lateral sc. Forecoxa yellow, with brown extreme base, mid and hind coxae brownish yellow; femora and tibiae yellow; foretarsomere 5 brown, mid and hind tarsomeres 4 and 5 brown, other yellow . Forefemur with rows of strong pd and pv, each longer than width of forefemur. Costal vein index 0.45, M vein index 2.3. Wing yellowish, veins yellow. Haltere white.