A taxonomic review of Japanese Asteia ( Diptera : Acalyptrata : Asteiidae )

The Japanese species o f Asteiidae are revised. Six species o f Asteia Meigen, 1830, are recorded here in addition to Astiosoma okinawae Sabrosky, 1957, hitherto recorded from Japan. Among them, Asteia gemina, A. longistylus, A. lunaris, and A. nigrigena are described as new to science. Asteia angustipennis Duda, 1934, and A. megalophthalma Duda, 1927, are recorded from Japan for the first time. There are conspicuous morphological differences in the male and female genitalia o f the seven species of Asteia. It is suggested that Asteia angustipennis, A. concinna, and A. gemina are very closely related and may be reproductively iso­ lated because o f their body markings and male genitalia. These species are assigned to the concinna group o f Asteia, newly desig­ nated in this study. A key to Japanese species and distribution maps are provided.

Asteiid flies have been recorded from all zoogeo graphical regions.The asteiid fauna of the Palaearctic Region is well-known, comprising 41 species assigned to four genera (Papp, 1984;Yang & Zhang, 1996;Carles-Tolra, 1998).Among them, 19 species and four genera are recorded from the area around Japan, such as Mongo lia, China, Korea, and the Far East of Russia (Duda, 1934;Papp, 1972Papp, , 1974;;Yang & Zhang, 1996).Tamaki (1997) and Kubo (2000) reported an undetermined spe cies of Asteia Meigen, 1830, from Honshu (Japan).From the Oriental Region, 11 species in three genera and an undetermined species of Phlebosotera Duda, 1927, are known.Among them, six species of Asteia and Astiosoma okinawae Sabrosky, 1957, have been recorded from Taiwan and the Ryukyus (Japan), respectively (Sabrosky, 1977).The knowledge of the Japanese fauna of Asteiidae is based on the original records for Astiosoma okinawae and undetermined species.However, it was expected that more species would be found in Japan, because there are 25 species in adjacent countries.
In this paper the results of a taxonomic study of Japa nese materials is presented.In addition to the Astiosoma okinawae, six species of Asteia are recognized based on the specimens collected throughout Japan.Among them, four species of Asteia are described as new to science and the other two species are recorded from Japan for the first time.Male and female genitalia of the species of Asteia are compared, and the diversity and usefulness of these structures for classification and reproductive isolation within the genus are discussed.Remarks.This species is distinguished from other con geners by the following characters: arista with long branches (Fig. 1a); interfrontal stripe of male extended anteriorly to anterior 1/4 of irons (Fig. 2a: is); face with white transverse band (Fig. 1a); 2 pairs of dorsocentral setae present; 2 notopleural setae present; scutellum yellow in ground colour, with semicircular dark brown marking dorsally.
Thorax entirely dark brown dorsally and yellow ven trally in ground colour; mesonotum entirely dark brown except yellow postalar wall; scutellum yellow in ground colour, with dark brown semicircular marking dorsally; propleural lobe and notopleuron dark brown; other tho racic pleura yellow in ground colour, without dark mark ings.Thoracic chaetotaxy: 2 dc, 2 npl, 2 kepst and 1 sctl all black; 6 minute dc anterior to large dc present; minute setula anterior to sctl present.
Wing (Fig. 3b) hyaline, 3.5 times longer than wide; veins pale brown; costal section between apices of R1 and R2+3 longer than R-M crossvein; apex of vein CuA1 reaching posterior margin of wing.Halter entirely yellow.
Legs entirely yellow.
Female similar to male in appearance except postab dominal structures: T6-8 and S6-8 broad plate-like; T8 and S8 shorter than T7 and S7 (Fig. 7a); T10 and S10 tri angular; cercus as long as T10 (Fig. 7a).Genitalia: ante rior 3/5 of vagina 3 times wider laterally and 2 times wider dorsoventrally than posterior 2/5 (Fig. Remarks.This species is distinguished from congeners by the following characters: arista with long branches (Fig. 6a); interfrontal stripe on male extending anteriorly to anterior 1/4 of frons (Fig. 2b); face yellow in ground colour, with pair of black markings on lateroventral side (Fig. 6a); 2 pairs of dorsocentral setae present; 2 notopleural setae present; scutum yellow brown except 2 pairs of longitudinal yellow brown areas; scutellum yellow in ground colour, with semicircular dark brown marking dorsally.It is very similar to A. concinna and difficult to distinguish from the latter species based on most of the male and female genitalia (Figs 6b-e, 7b-d, 8b-e).However, A. gemina differs from A. concinna in that the male distiphallus bears a broad curtain-like sclerite (Fig. 6d-e: y).

Description
Male.Head (Fig. 9a) higher than long; frons dark brown except yellow brown anterior 1/4, entirely bare; orbital plate and ocellar triangle dark brown in ground colour, polished; anterior apex of interfrontal stripe reaching anterior margin of anterior ocellus but not beyond it (Fig. 2c); face dark brown in ground colour, with white transverse band on ventral half; parafacial dark brown; gena yellow; occiput and dorsal half of postgena dark brown; ventral half of postgena yellow.Head chaetotaxy: 1 orbital, 1 ocellar, 1 inner vertical, 1 outer vertical, 1 postocellar, 1 vibrissal, 4 subvibrissal, 1 genal and several postgenal setae all black; 2 minute setulae anterior to orbital seta present.Scape and pedicel of antenna dark brown in ground colour, postpedicel yellow brown in ground colour, dorsal 1/3 of postpedicel dark brown; arista black, with 3 dorsal and 2 ventral branches; pedicel with long seta dorsally; postpedicel covered with white setulae.Mouth parts yellow.
Thorax entirely yellow in ground colour, with dark brown markings; mesonotum entirely dark brown except yellow postalar wall, scutellum entirely yellow; propleural lobe and notopleuron dark brown; thoracic pleura yellow in ground colour, katepisternum and katepimeron without dark markings.Thoracic chaetotaxy: 2 dc, 1 prst, 1 pal, 2 npl, 2 kepst, and 1 sctl all black; 3 minute dc present posterior to transverse suture; prst as short as dc posterior transverse suture; minute setula present ante rior to sctl.
Wing (Fig. 3c) hyaline, 3 times longer than wide; veins pale brown; costal section between apices of R1 and R2+3 shorter than R-M crossvein; apex of vein CuA1 close to posterior margin of wing but not reaching it.Halter yel low, knob dark brown.
Legs entirely yellow.
Remarks.This species is distinguished from other con geners by the following characters: arista with long branches (Fig. 9a); interfrontal stripe of male extended anteriorly to anterior ocellus (Fig. 2d: is); face with white transverse band (Fig. 9a); 2 pairs of dorsocentral setae present; scutellum entirely yellow; katepisternum without dark marking; abdominal tergites of male lacking dark markings except 5th abdominal tergites with pair of dark markings.It is very similar to A. chinica Yang & Zhang, 1996, in appearance but differs from it by wing veins Ri and R2+3 very close, length between apices of them shorter than R-M crossvein (Fig. 3c), knob of halter dark brown, and 1-4th abdominal tergites of male lacking dark mark ings.It is also similar to A. megalophthalma Duda, 1927, but differs from the latter in the absence of postocellar seta (Fig. 9a), katepisternum and katepimeron without dark markings, and 5th abdominal tergite with paired dark markings.

Description
Male.Head (Fig. 11a) higher than long; anterior half of frons yellow brown, posterior half dark brown, entirely bare; orbital plate and ocellar triangle dark brown in ground colour, polished; anterior apex of interfrontal stripe slightly beyond anterior ocellus (Fig. 2e: is); face dark brown in ground colour, with white transverse band on ventral half; parafacial and gena dark brown; occiput and dorsal half of postgena dark brown; ventral half of postgena yellow.Head chaetotaxy: 1 orbital, 1 ocellar, 1 inner vertical, 1 outer vertical, 1 vibrissal, 2 subvibrissal, 1 genal and several postgenal setae all black; postocellar seta absent; minute setula present anterior to orbital seta.Scape and pedicel of antenna dark brown in ground col our; postpedicel yellow brown in ground colour, dorsal 1/3 of postpedicel dark brown; arista black, with 3 dorsal and 2 ventral branches; pedicel with long seta dorsally; postpedicel covered with white setulae.Mouth parts yel low.
Thorax entirely yellow in ground colour, with dark brown markings; mesonotum entirely dark brown except yellow postalar wall, scutellum entirely yellow; propleural lobe and notopleuron dark brown; thoracic pleura yellow in ground colour, katepisternum and katepimeron with longitudinal dark brown markings.Thoracic chaetotaxy: 2 dc, 1 pal, 2 npl, 2 kepst and 1 sctl all black; 3 minute dc present posterior to transverse suture; minute setula present anterior to sctl.
Wing (Fig. 3d) hyaline, 3 times longer than wide; veins pale brown; costal section between apices of R1 and R2+3 shorter than R-M crossvein; apex of vein CuA1 close to posterior margin of wing but not reaching it.Halter yel low, knob dark brown.
Legs entirely yellow.
Body length 1.5 mm; wing length 2.1 mm, width 0.7 mm.Etymology.The specific epithet refers to the crescent marking on the katepisternum.
Remarks.This species is distinguished from other con geners by the following characters: interfrontal stripe of male extended anteriorly to anterior ocellus (Fig. 2e: is); face with white transverse band (Fig. 11a); 2 pairs of dorsocentral setae present; scutellum entirely yellow; katepisternum with dark marking; abdominal tergites of male lacking dark markings except 5th abdominal tergite with transverse dark marking.It is very similar to A. chinica in appearance but differs from it in wing veins R1 and R2+3 being very close, length between apices of them shorter than R-M crossvein (Fig. 3d), knob of halter dark brown, 1-4th abdominal tergites of male lacking dark markings, and 5th abdominal tergite of male with unpaired transverse dark marking.Tamaki (1997) reported an undetermined species of Asteia from Saitama Prefecture, Japan.I examined this series of the specimens and found that one of them belongs to this species.Remarks.This species is distinguished from congeners by the following characters: arista with long branches (Fig. 12a); face with white transverse band (Fig. 12a); gena dark brown (Fig. 12a); 2 pairs of dorsocentral setae present; scutum entirely dark brown; scutellum entirely yellow; katepisternum with dark marking.Asteia nigrigena sp.n.(Figs 2f,3f,5, Asteia sp.; Tamaki, 1997: 148. (in part.)

Description
Male.Head (Fig. 13a) higher than long; anterior half of frons yellow brown, posterior half dark brown, entirely bare; orbital plate and ocellar triangle dark brown in ground colour, polished; anterior apex of interfrontal stripe slightly beyond anterior ocellus (Fig. 2f); face dark brown in ground colour, with white transverse band on ventral half; parafacial and gena dark brown; occiput and dorsal half of postgena dark brown; ventral half of postgena dark yellow.Head chaetotaxy: 1 orbital, 1 ocellar, 1 inner vertical, 1 outer vertical, 1 vibrissal, 2 subvibrissal, 1 genal and several postgenal setae all black; postocellar seta absent; minute setula present anterior to orbital seta.Scape and pedicel of antenna dark brown in ground col our; postpedicel yellow brown in ground colour, dorsal 1/3 of postpedicel dark brown; arista black, with 3 dorsal and 2 ventral branches; pedicel with long seta dorsally; postpedicel covered with white setulae.Mouth parts yel low.
Thorax entirely yellow in ground colour, with dark brown markings; mesonotum entirely dark brown except yellow postalar wall, scutellum entirely yellow; pro pleural lobe and notopleuron dark brown; thoracic pleura yellow in ground colour, katepisternum and katepimeron with longitudinal dark brown markings.Thoracic chaetotaxy: 2 dc, 1 pal, 2 npl, 2 kepst and 1 sctl all black; 3   posterior margin of wing but not reaching it.Halter yel low, knob dark brown.Legs entirely yellow.
Remarks.This species is distinguished from congeners by the following characters: interfrontal stripe of male extended anteriorly to anterior ocellus (Fig. 13a); face with white transverse band (Fig. 13a); 2 pairs of dorsocentral setae present; scutellum entirely yellow; katepisternum with dark marking; abdominal tergite of male lacking dark markings except 5th abdominal tergite with transverse dark marking.It is very similar to A. chinica in appearance but differs from it in wing veins R1 and R2+3 being very close, length between apices shorter than R-M crossvein (Fig. 3f), knob of halter dark brown, 1-4th abdominal tergites of male lacking dark markings, and 5th abdominal tergite of male with unpaired transverse dark marking.It also differs from A. longistylus and A. lunaris by postgena entirely dark brown (Fig. 13a).Tamaki (1997) and Kubo (2000) reported an undeter mined species of Asteia, respectively.I examined their specimens and found that some of them belong to this species.

DISCUSSION
More than 100 species of the Asteiidae have been described from all over the world since Meigen's (1830) description of A. amoena Meigen, 1830.Male genitalia of some species of this family have been described and illus trated briefly by authors.However, there are few reports comparing the male genitalia of species and the female genitalia, e.g.vagina and ventral receptacle have not been described, except the spermathecae.
In this study I examined eight species of Asteia, including A. amoena and A. concinna and found distinct differences in male and female genitalia of these species.Five of the species could be classified into two groups based on the morphology of the male distiphallus: the A .  with a pair of lateral sclerites as in the A. concinna group and the mesal tube contains a complex sclerite in front of the basal tube (Fig. 11c; Papp, 1998, Fig. 25.11).The left lateral sclerite (Fig. 11c: L) of this group is terminated abruptly and touches the anterior margin of the mesal tube.The right lateral sclerite (Fig. 11c: R) is tapered api cally and becomes indistinct at the anterior margin of the mesal tube.The mesal tube of the distiphallus meets the basal part tube of the distiphallus at an acute angle, and bears a slender wire-like apical process in A. lunaris (Fig. 11c), but terminates in a triangle short apex in A. amoena (Papp, 1998: Fig. 25.11).Asteia longistylus and A. nigri gena do not belong to either of the above groups.The dis tiphallus of A. longistylus is characterized by the absence of the sclerotized part as in the lateral sclerites of the A. amoena and the A. concinna groups (Fig. 9d).The distiphallus of A. nigrigena characteristically lacks the lateral sclerites basally and has a wire-like elongation longer than the remaining portion of the phallus and a short appendix on the basal portion of distal wire-like elonga tion (Fig. 13c).Males of A. megalophthalma are unknown.
Female genitalia consist of the vagina, ventral recep tacle 12c,14b: vg,vr), pair of accessory glands, and spermathecae (Figs 4d,7d,8e,10d,12d,14c).These structures are entirely membranous in the species examined and difficult to compare, but the following characters could be observed.In the female genitalia of the A .concinna group, the vagina has a ven tral pocket    12c, 14b: II) as in the A. concinna group.However, the expanded section does not have a spindle-like part and the narrow section is as long as or longer than the expanded section in these species.The spermatheca (Figs 10c, 12c, 14b: III) is approximately as long as the expanded section of the spermathecal duct in these species.The female of A. lunaris is unknown.
There is a marked difference in the morphology of male and female genitalia of species in the A .concinna group and the other five species.The right lateral sclerite has a pointed apex, the distiphallus a spirally twisted apex and spinose tubercles, the vagina a flattened ventral floor and ventral pocket in species of the A. concinna group.Although the position of the male distiphallus within the female vagina during copulation is unclear, the shapes of the distiphallus may affect the female vagina of this group in different ways than in other species when copulating.
The A .concinna group may be assigned to a new genus or subgenus based on the above morphological features.However, it is necessary to precisely compare the mor phological features of the 70 species assigned to Asteia.These species must be classified into several monophyle-tic units, such as the A. concinna and A. amoena groups, and autapomorphic characters defining each group, such as the spirally twisted apex in the distiphallus of A. concinna group, recognized.The male distiphallus and female genitalia are useful and excellent characters for the classification of the species of Asteia.
It is worth noting, the similarities in the morphological and geographical distribution patterns of the species of the A. concinna group.Asteia gemina is very similar to A. concinna in external appearance and female genitalia but differ in the shape of the left lateral sclerite of the male distiphallus (Figs 6d, 8b).The former species distinctly differs from A. angustipennis in body colour and mark ings, but has very similar male and female genitalia (Figs 1b-f, 6b-e).Preliminary distribution ranges for these spe cies were compiled in this study.Asteia concinna was originally known only from Europe, but Yang & Zhang (1996) recorded it from China.Asteia angustipennis and A. gemina are known only from the Asian part of Russia and Japan.In Hokkaido, Japan, they are sympatrically distributed geographically and temporally.Asteia concinna and A. gemina are distributed allopatrically as far as is known.At the present, the phylogenetic relation ships between these three species of the A. concinna group and other species of Asteia are unresolved.How ever, morphological similarities between these species suggest that they are closely related and their morpho logical characters reflect reproductive isolation.The male distiphallus in A. concinna and A. gemina differ greatly in shape (Figs 6d-e, 8b), but morphological features of the female vagina are not distinctly different in these two spe cies .Therefore, A. concinna and A. gemina may be isolated by differences in male genitalia and their geographical distributions, with the latter more important than the former.Asteia angustipennis and A. gemina differ in body markings and it is possible that these species may be more isolated from one another than A. concinna and A. gemina.

Fig. 9 .
Fig. 9. Male (holotype) o f Asteia longistylus sp.n. a -head in left lateral view; b -epandrial complex in caudal view; c -epandrial and hypandrial complex in left lateral view; d -distiphallus in left lateral view.Scale bars: a = 0.30 mm; b-d = 0.05 mm.Refer to the text for the abbreviations.
Fig. 11.Male (holotype) o f Asteia lunaris sp.n. a -head in left lateral view; b -epandrial complex in caudal view; c -distiphallus on in left lateral view.Scale bars: a = 0.33 mm; b-c = 0.10 mm.Refer to the text for the abbreviations.

Fig. 13 .
Fig. 13.Male (holotype) o f Asteia nigrigena sp.n. a -head in left lateral view; b -epandrial complex in caudal view; c -geni talia in left lateral view.Scale bars: a-b = 0.25 mm; c = 0.13 mm.Refer to the text for the abbreviations.
amoena and A. concinna groups.Asteia angustipennis, A. concinna and A. gemina belong to the latter group.Their male distiphallus in the A .concinna group consists of a pair of lateral sclerites elongated apically and bearing plate-like sclerites (Figs 1e-f, 6d-e, 8b: 8, y), and with a spiral apex (Figs 1e-f, 6d-e, 8b: p).Of the lateral sclerites of the distiphallus, the right lateral sclerite is directed anterodorsally and has a spine-like projection apically (Figs 1f, 6d-e: a).The left lateral sclerite is directed anteroventrally and has a half-pipe plate-like sclerite (Figs 1e-f, 6d-e, 8b: 8) under and supporting the apex of the distiphallus.In A. angustipennis and A. gemina, this sclerite bears a curtain-like sclerite (Figs 1e-f, 6d-e: y).The apex of the distiphallus of the concinna group has a series of spiral folds (Figs 1e-f, 6d-e, 8b: p 1-3) as if it was twisted spirally.The apical half of these folds bear numerous spinose tubercles.Asteia amoena and A. lunaris belong to the A .amoena group.Their male distiphallus consists of the basal tube
in posterior 2/5 and flattened stiff ventral floor (Figs 4c, 7c, 8d: vf).The apex of the ventral receptacle (Figs 4b-c, 7b-c, 8c-d: vr) is expanded and rounded.The expanded section of the spermathecal duct (Fig. 4d: II) is longer than two times the narrow section (Fig. 4d: I).The distal half of the expanded section is spindle-like.The spermatheca (Fig. 4d: III) is as long as the spindle part of the expanded sec tion of the spermathecal duct.Although the morpho logical differences in the male distiphallus of A. amoena, A. longistylus, and A. nigrigena are distinct (Figs 9d, 13c; Fig. 25.11 in Papp, 1998), the female genitalia of these species and A. megalophthalma are very similar.The vagina (Figs 10c, 12c, 14b: vg) of these species is simpler than that of the A .concinna group and the flattened ven tral floor and ventral pocket in the vagina are absent.The ventral receptacles (Figs 10c, 12c, 14b: vr) are pigmented along the apex.The spermathecal ducts also have a narrow section (Figs 10c, 12c, 14b: I) and an expanded section (Figs 10c,