Chaomyia qinghaiensis C. Zhang & Cerretti, sp. nov., by present designation.

Tribe Affiliation. Chaomyia qinghaiensis gen. & sp. nov. exhibits several characteristic morphological features, including a strongly protruding lower facial margin, which is well visible in front of vibrissal angle, a bare prosternum, and preapical anterodorsal seta of the fore tibia only slightly shorter than the preapical dorsal seta. Moreover, its male terminalia display a tergite 6 that is not longitudinally divided into hemitergites, a weakly sclerotized lateroventral area of distiphallus, and basiphallus that runs nearly parallel to distiphallus. This combination of likely derived character states is consistent with the assignment of the genus to the subfamily Tachininae (Tschorsnig and Herting 1994; Cerretti et al. 2014).

Recent phylogenetic reconstructions based on molecular data support Tachininae as a monophyletic group, with the exclusion of Macquartini and Myiophasiini, a clade of parasitoids of beetle larvae that is widely distributed globally (Stireman et al. 2019). Adult Macquartiini and Myiophasiini share having males with strongly narrow frons, a body ground color which is mostly black and, although very variable, a male phallus lacking a sclerotize medioventral sclerite, and cerci not fused into a syncercus. Chaomyia has male cerci fused into a syncercus, membranous posterior sclerite of distiphallus, well-developed anepimeral seta, male hypandial arms that are posteromedially fused and completely encircle the base of the phallus, male epandrium with setae dorsally, and a distinctly shaped medioventral sclerite of the distiphallus (see O’Hara 2002, who described this as the anterior sclerite of the distiphallus). For these reasons, we think Chaomyia cannot be assigned to either of these two tribes.

Chaomyia shares most of the putative synapomorphies identified by O’Hara (2002) supporting the monophyly of the tachinine tribe Polideini. However, it lacks certain diagnostic features: the male surstylus in Chaomyia is nearly bare apically, rather than bearing spine-like setae; male sternite 5 possesses micropubescence along the inner margin of the posteromedian cleft, rather than distinct microspines; and the posterior thoracic spiracle is not uniformly haired on both sides but instead is covered by flap-like setulae originating only from its posterior margin. We interpret these morphological differences as evidence that Chaomyia could represent a member of the Polideini, pending confirmation of its phylogenetic position through molecular data.

In the key to Palaearctic genera by Tschorsnig and Richter (1998: 756, 772, 777), our specimens key out to Synactia Villeneuve of the tribe Ernestiini. However, Synactia differs from Chaomyia in several respects, including: densely hairy eyes, facial ridge with setae on lower 2/5 to 2/3, lower facial margin not protruding forward, arista thickened on basal 1/2 or more, R₄₊₅ with setulae at the base, and median excavation of syntergite 1+2 reaching to hind margin. Given these differences, Chaomyia cannot be confidently placed within Synactia or most other members of Ernestiini. Nevertheless, the available morphological evidence provisionally supports the assignment of Chaomyia to either the tribe Polideini or Ernestiini, pending further study.

Following a thorough examination and comparison of C. qinghaiensis sp. nov. with both collection material and scientific literature (Crosskey 1976; Wood 1987; Tschorsnig and Richter 1998; Wood and Zumbado 2010; Cerretti et al. 2012), we conclude that it exhibits a unique combination of morphological traits among Tachininae. This combination of characters is considered apomorphic, providing a strong justification for the establishment of a new genus to accommodate the species from Halejing.

Male and female. Small-sized tachinid flies.

Head (Fig. 2A, B, E, F). Eyes nearly bare, with sparse very short ommatrichia. Frons 1.26–1.41 (male) and 1.33–1.60 (female) of eye width. Frontal vitta slightly narrower than fronto-orbital plate in front of ocellar triangle. Parafacial bare, at most as wide as postpedicel in anterior view. Face without facial carina; lower margin of face distinctly protruding forward in front of vibrissal angle and visible in lateral view. Gena 0.5–0.6 of eye height. Fronto-orbital plate with 5–7 inclinate frontal setae; 4–5 outer orbital setae, anterior one or two proclinate, posterior two or three lateroclinate in male; 4 outer orbital setae, anterior one proclinate and posterior three lateroclinate in female. Occiput with only black hairs behind postocular row, ventral part bulging. Arista bare, thickened at basal 1/3 to 2/5. Palpus about 3/4 as long as postpedicel, with 2–3 apical setae. Prementum 7–8 times as long as wide. Labellum small.

Figure 2. 

Chaomyia qinghaiensis sp. nov. A–D, ♂; E–H, ♀. A, E, C, G head and body in lateral view B, F head in anterior view D, H body in dorsal views. Scale bars 0.5 mm (A, B, E, F); 1.0 mm (C, D, G, H).

Thorax (Fig. 2C, D, G, H). Body densely covered with yellowish pruinosity. Prosternum bare. Postpronotal lobe with two setae and some hairs; first postsutural supra-alar seta about as long as the first postsutural intra-alar seta; one anepimeral seta extending to posterior margin of upper calypter. Scutellum entirely black, with 3 pairs of marginal setae, subapical scutellar seta not extending back to apices of strong crossed apical scutellar setae. Spiracles dark and small; posterior spiracle posterior fringe visibly larger than anterior fringe, proepimeral setae directed upward. Base of vein R₄₊₅ with 2–4 small setulae dorsally and ventrally.

Wing membrane around crossveins r-m and dm-cu darkened. Vein M evenly bent, bluntly angled, extending to wing margin making cell r₄₊₅ closed at wing margin or merged to vein R₄₊₅ to form a very short petiole.

Leg. Fore claws and pulvilli shorter than 5^th tarsomere. Fore tibia with 2–3 short anterodorsal, 2 posterior and 1 posterodorsal setae, preapical anterodorsal seta approximately as long as preapical dorsal seta or just slightly shorter. Hind tibia with 2 preapical dorsal setae, preapical anteroventral seta about as long as preapical posteroventral seta.

Abdomen. Mid-dorsal depression on abdominal syntergite 1+2 not reaching to hind margin. Syntergites 1+2 to tergite 4 each with dark transverse band only on lateral posterior 1/4–1/5. Sternite 1 hairy; the other sternites exposed.

Male terminalia (Fig. 3A–H). Tergite 6 not divided medially into two hemitergites. In ventral view, sternite 5 nearly square with a deep, U-shaped median cleft which is approximately 1/2 length of the sternite; lateral lobe of sternite 5 with an inner protrusion bluntly rounded apically. In caudal view, cerci fused to form a syncercus, narrowed on apical 2/3 and pointed, not separated apically; surstylus narrowed and bent inwardly and blunt apically. In lateral view, syncercus longer than surstylus, bent backward apically; surstylus thick, bluntly round apically, without teeth or spines apically. Hypandrium broadly expanded posteriorly on both sides, hypandrial arms narrowly fused dorsally; pregonite broad, lobe-like; postgonite pointed apically; phallus well developed, basiphallus with a weakly sclerotized epiphallus in distal position; medioventral ridge of distiphallus present and well developed; lateroventral region of the distiphallus membranous, ejaculatory apodeme large and process fan-shaped.

Figure 3. 

Chaomyia qinghaiensis sp. nov. A–H, ♂, A, E; B, F cerci, surstyli and epandrium of male in caudal and lateral views C, G phallus (aedeagal apodeme, ejaculatory apodeme, hypandrium, epiphallus, pregonite, postgonite, basiphallus and distiphallus) of male in lateral view D, H sternite 5 in ventral view. Scale bars: 0.1 mm.

Female terminalia (Fig. 4). Sternite 5 nearly square, with median and posterior setae; tergites 6–8 not divided into 2 hemiterigites, with a row of strong setulae; sternites 6–8 with posterior setulae.

Figure 4. 

Chaomyia qinghaiensis sp. nov. ♀ Female abdomen in ventral view A postabdomen B abdomen C postabdomen in detail, st = sternite, tg = tergite, sternites 5, 6, 7, 8 and tergites 6, 7, 8.

China: Halejing, 3178.7 m, Haiyan County, Haibei Prefecture, Qinghai Province (Fig. 1).

The genus name is formed by the name of Chao Cheiming (= Zhao Jianming), a late Chinese dipterologist, plus the Greek myia, meaning “fly”, in memory of Chao’s great contributions to Tachinidae taxonomy of China. Chaomyia is treated as feminine.

Holotype : China • ♂ (SYNU-QH 230001); Qinghai Province; Haiyan County, Haibei Tibetan Autonomous Prefecture, Halejing Mongolian Village; 100.9977°N, 37.0342°E; 3178.7 m elev., 5.IX.2023; Malaise trap-Jiayi Ji (SYNU). Paratypes: • 4 ♂ 4 ♀ (SYNU-QH 230002-9), same data as holotype (Fig. 1).

Eyes nearly bare. Head and body densely covered with yellowish pruinosity. Frons more than eye width in both sexes, fronto-orbital plate of male with 5 to 7 inclinate frontal setae, 1~2 proclinate outer orbital setae and 2~3 lateroclinate outer orbital setae, gena height 0.5–0.6 of eye height, lower facial margin distinctly protruding forward, occiput with only black setulae. Wing with dark clouded at crossveins r-m and dm-cu. Male fore claws and pulvilli shorter than 5^th tarsomere. Mid-dorsal depression of abdominal syntergite 1+2 extending on basal half, sternites well exposed.

Male. Body length 4.5–5.2 mm.

Head (Fig. 2A, B). Eyes nearly bare, with only sparsely whitish short ommatrichia. Frontal vitta reddish brown. Frontal-orbital plate and parafacial covered with yellow pruinosity. Gena reddish brown. Antenna and arista black. Palpus dark brown. Prementum gleaming black. Frons 1.26–1.41 times of eye width. Frontal vitta slightly narrower than fronto-orbital plate in front of ocellar triangle. Parafacial bare, at most as wide as postpedicel in frontal view, as wide as postpedicel in lateral view. Median facial carina absent, lower facial margin distinctly protruding forward in front of vibrissal angle. Gena height about as long as postpedicel, 0.5–0.6 of eye height; genal dilation well developed. Fronto-orbital plate wide, with 2 rows of setae, 5 to 7 inclinate frontal setae, reaching on parafacial, the middle of pedicel; 1–2 proclinate outer orbital setae and 2–3 lateroclinate outer orbital setae; 2 ocellar setae situated between the anterior and posterior ocelli, proclinate, well developed, nearly as long as frontal setae close to ocellar triangle. Inner vertical seta about 0.7 of eye height; outer vertical seta 2/3–3/4 as long as inner vertical seta. Facial ridge more or less straight, with more or less erect short setae on lower 1/3. Vibrissa inserted level with lower facial margin or below, slightly longer than subvibrissal setae; subvibrissal ridge with 4–5 strong subvibrissal setae mixed with some fine setulae. Postpedicel 2.0–2.3 times as long as pedicel; pedicel with 1 long seta on dorsal surface, which is slightly longer than pedicel. Arista thickened on basal 1/3 to 2/5, about as long as antenna, 2^nd aristomere 2.0–2.5 times as long as wide. Palpus filiform, not apically enlarged, about 3/4 as long as postpedicel, with 2–3 apical setae. Prementum 7–8 times as long as its diameter. Labellum small.

Thorax (Fig. 2C, D). Scutum covered with yellow pruinosity and four dark longitudinal vittae on dorsum, presutural inner vitta about 1/4 as wide as pruinose portion between inner and outer vittae, presutural outer vittae approximately triangular; inner vittae only on anterior 1/3 of postsutural scutum. Two presutural and 2 postsutural acrostichal setae; 2 presutural and 3 postsutural dorsocentral setae; 2 postsutural intra-alar setae separated by a distance greater than the distance between the first seta and the suture; first postsutural supra-alar seta slightly longer than notopleural setae, about as long as the first postsutural intra-alar seta. Scutellum with 3 pairs of marginal setae, subapical scutellar seta not extending back to level of apices of strong crossed apical scutellar setae and tilted upwards by 30–60°. Prosternum bare; postpronotal lobe with two setae; proepisternum bare; anepisternum with two antero-upper weak setae and a row of 4–6 posterior setae. Anepimeron with 1 seta extending to anterior 1/2 of lower calypter; katepisternum with 3 setae (2 anterior and 1 posterior, anterior-lower one weaker) with 3 seta-like hairs between anterior and posterior setae. Katepimeron bare. Anatergite below calypter and katatergite bare. Posterior spiracle small and posterior fringe visibly larger than anterior fringe. Postmetacoxal area membranous.

Wing long and narrow, hyaline, brownish. Tegula and basicosta dark brown. Second costal section bare ventrally, costal spine short or absent. Base of R₄₊₅ with 2–4 small setulae dorsally and ventrally. Relative lengths of 2^nd, 3^rd and 4^th costal sectors approximately 1:4:2. Vein M evenly bent, bluntly angled, extending to wing margin, making cell r₄₊₅ closed or short petiolate. Costal sector 4 distinctly longer than costal sector 6. Section of vein M between r-m and dm-cu about as long as section between dm-cu and bend of M. Crossvein dm-cu nearly straight and not exceptionally oblique. Section of vein M between dm-cu and bend at least 2 times distance between the bend and wing posterior margin. Vein CuA₁ bare. Lower calypters milky white with yellowish, bare on dorsal surface, inner edge of lower calypters close to outer edge of scutellum, its outer margin not strongly convex. Halter brownish yellow, only darker at apex and larger than posterior spiracle.

Leg dark brown. Fore claws and pulvilli shorter than 5^th tarsomere. Fore tibia with 2–3 short anterodorsal, 2 posterior and 1 posterodorsal setae, preapical anterodorsal seta slightly shorter or approximately as long as preapical dorsal seta or just slightly shorter. Mid femur with 1 anterior, 1 preapical dorsal seta and a row of posteroventral setae on basal half; mid tibia with 2 anterodorsal, 2–3 posterior and 1 ventral setae. Hind coxa bare on posterodorsal surface; hind femur separately with a row of anteroventral, posteroventral setae and anterodorsal setae, 2 posterodorsal setae on apical 1/3; hind tibia with 3–4 anterodorsal, 3 posterodorsal and 2 ventral setae, 2 preapical dorsal setae, preapical anteroventral seta about as long as preapical posteroventral seta.

Abdomen long ovate, almost covered with grayish-yellow pruinosity, tergites not fused dorsally, syntergite 1+2 to tergite 4 each with dark transverse band on lateral posterior 1/5. Mid-dorsal depression of syntergite 1+2 extending on the proximal half, syntergite 1+2 with 2 median marginal and 1–3 lateral marginal setae. Tergite 3 with 2 median marginal and 2 weak median discal setae, 1 pair of lateral marginal and 2 pairs of lateral discal setae. Tergite 4 with a row of marginal setae, 2 median discal and 2 pairs of lateral discal setae. Tergite 5 inverted trapezoid-like, approximately the same length as tergite 4, with a row of a marginal setae, 2 median discal setae, 2–3 pairs of lateral discal setae. Ventral surface of tergites 4 and 5 covered with thin decumbent hairs on a shiny, non-pruinose cuticle. Sternite 1 hairy, the other sternites exposed; sternites 2 to 4 each with 3–4 setae on posterior portion. Sternite 5 and male terminalia are the same as generic descriptions as shown in Fig. 3A–H.

Female (Figs 2E–H; 4). Frons 1.33–1.60 of eye width. Parafacial equal or slightly wider than postpedicel in frontal view, wider than postpedicel in lateral view. Gena higher than antennal length in lateral view. Six pairs of frontal setae. Postpedicel 1.5–2.0 times as long as pedicel. Mid tibia with 4–5 posterodorsal setae. Hind tibia with 2–3 ventral setae. Abdominal syntergite 1+2 without median marginal seta; tergite 5 inverted cone-like. Other features are same as in male.

China: Halejing, 3178.7 m, Haiyan County, Haibei Prefecture, Qinghai Province (Fig. 1).

The species name is taken from the type locality, Qinghai Province, China. Adjective.