A review of the Delia interflua group with descriptions of two new species (Diptera, Anthomyiidae)

Abstract The Delia interflua group is reviewed to include 16 species. Two new species are described, namely Delia subnemostylata Xue & Du, sp. n., Delia nigeriposticrus Xue & Du, sp. n. A catalogue and amended key to new species of this group are also included.


Introduction
The genus Delia Robineau-Desvoidy, 1830 belongs to the dipteran family Anthomyiidae. More than 310 species in this genus (excluding Neotropical species) are known from around the world (Hennig1974, Ackland and Pont 1977, Fan et al. 1988, Pont 1989, Griffiths 1991, Dely-Draskovits 1993, Wei et al. 1996, Ackland 2008, Xue and Du 2008, Xue and Du 2009, Wang et al. 2014, Du and Xue 2017. The Delia interflua group is a small group and can be recognized by the following characters: the apices of the sternite V processes dilate and rounded, except for D. subnemostylata sp. n.; cercal plate with long setae; surstyli elongated, except for D. kullensis; usually the acrophallus is supported by a sclerotized bridge between the bases of the free paraphallic processes; the sclerotized bridge is prolonged downwards, forming a membranous process (Griffiths 1991, Xue andDu 2008). In this work, two new species of this group are described, Delia subnemostylata Xue & Du, sp. n., Delia nigeriposticrus Xue & Du, sp. n. The key produced by Wei et al. (1996) is here modified to include three couplets leading to the identification of the new species.

Materials and methods
All specimens were collected from Yunnan province of China. Type specimens are deposited in the Diptera collection of the Institute of Entomology, Shenyang Normal University (IESNU). They were examined under an Olympus SZ-ST stereomicroscope. Morphological terminology is based mainly on that of McAlpine (1981 Description. Holotype male. Body length 5.5 mm.
Head. Eyes only with several short ciliae in lower margin; frontal vitta red brown in lower part, remaining black, 2.0 times as wide as fronto-orbital plate; frons 1.5-2.0 times as wide as anterior ocellus; frontal vitta with a pair of inter frontal setae; without orbital setae; frontal setae 4-5 pairs, situated on lower half; fronto-orbital plate, parafacial with dark gray tomentum, parafacial 1.3 times as wide as postpedicel; antenna black, postpedicel 2.0-2.3 times as long as broad; arista pubescent, the longest aristal hairs shorter than its basal diameter; lower facial margin not projecting, vibrissal angle and frontal angle in the same vertical plane in profile; gena sparsely with dark gray tomentum, genal height approx. 1/4 of eye height; anterior margin of gena with two rows of upcurved subvibrissal setulae; postocular setae extending to ventral surface, epicephalon haired; proboscis short, prementum with gray tomentum sparsely, 2.5 times as long as broad, palpus black, equal to the length of prementum.
Wing. Base brown and basicosta fuscous; costa setulose only basally on ventral surface, anterior surface with a row of pectinated spines; costal spine subequal to crossvein r-m; radial node bare, calypters yellowish, lower calypter approx. 2/5 length of upper one; halter yellow.

Remarks.
This new species is similar to D. nemostylata Deng & Li, 1984 as it has very similar genitalia, but differs from it for its frontal setae 4-5 pairs, katepisternal seta 1+2; lower calypter approx. 2/5 length of upper one; fore tibia with one submedial ad and one medial p; mid tibia without pv; hind tibia with two ad and three pd.
Etymology. This new species is similar to D. nemostylata Deng & Li, 1984. Hence, its epithet is derived to reflect this relationship.
Description. Holotype male. Body length 5.0-5.2 mm. Head. Eye bare; frontal vitta black, line form at the narrowest part; frons as wide as anterior ocellus; frontal vitta with 2 pairs of interfrontal setae; without orbital setae; 7 pairs of frontal setae, situated on lower half of frons; fronto-orbital plate and parafacial with fuscous tomentum; parafacial 1.2 times wider than postpedicel; antenna black, postpedicel 1.5-2.0 times longer than broad; arista pubscent, the longest hair shorter than its basal diameter; vibrissal angle situated behind frontal angle in profile; genal height approx. 1/4 eye height; anterior margin of gena with 2 rows of upcurved subvibrissal setulae; postocular setae extending to ventral surface, epicephalon bare; prementum mostly with gray tomentum, 5.0 times longer than broad; palpus short and black, not more than half length of prementum.
Wing. Base fuscous, basicosta black; costa setulose only basally on ventral surface; costal spine short; radial node bare, calypters brown yellow; lower calypter approx. 1/3 length of upper one; halter yellow. Legs. Entirely black; fore tibia with single medial p; mid femur with a complete Delia conjugata Deng & Li, 1994 Distribution. China: Gansu, Wenxian. Note. A body covered with more hair is a characteristic that distinguishes this species from other species of this species group.