﻿A review of the subgenus Loxocera Meigen, 1803 (Diptera, Brachycera, Psilidae) in China

﻿Abstract The subgenus Loxocera (Loxocera Meigen, 1803) (Diptera, Brachycera, Psilidae) in China is reviewed. Six species are recognized, including four new species: L. (L.) chikunisp. nov., L. (L.) lonsdaleisp. nov., L. (L.) maculithoraxsp. nov., and L. (L.) obscurasp. nov. Two species originally placed in the subgenus Loxocera, L.anulata Wang & Yang, 1998 and L.tianmuensis Wang & Yang, 1998, are transferred to the subgenus Loxocera (Imantimyia Frey, 1925). A key to the species of the subgenus Loxocera occurring in China is provided.


Introduction
Psilidae is a group of small to medium-sized, yellow to black acalyptrate flies which can be diagnosed externally by their peculiar wing venation and reduced setation (Lonsdale 2020;Shatalkin 2021).With about 340 species described so far, the Psilidae is distributed in all zoogeographic regions, with the highest diversity occurring in the temperate areas of the northern hemisphere (Shatalkin and Merz 2010;Lonsdale 2020).The monophyly of Psilidae and its several subtaxa are well supported, whereas the generic classification within Psilinae needs further consideration (Buck andMarshall 2006a, 2006b;Lonsdale 2020;Zhou and Yang 2022).
In the present study, we review and key the Chinese fauna of the subgenus Loxocera and document six species, four of which are described here as new.The other two Chinese species previously placed in the subgenus Loxocera are here transferred to Imantimyia.Outside of China, an additional eight species of the subgenus Loxocera are known, with these occurring exclusively within the Palaearctic and northern Oriental realms (Iwasa 1992(Iwasa , 1993;;Buck and Marshall 2006b;Zhou et al. 2022).A checklist for all described species of the subgenus Loxocera is also provided in this paper.

Materials and methods
Specimens examined in this study are deposited in the Entomological Museum of China Agricultural University, Beijing, China (CAU) and the Smithsonian National Museum of Natural History, Washington, DC, USA (USNM).
Male terminalia were prepared by macerating the apical portion of the abdomen in heated 10% KOH solution for approximately 10 min, and then rinsing in distilled water.External structure and terminalia were examined using a Nikon SMZ745 stereoscopic microscope.After examination, the terminalia were transferred to fresh glycerol and stored in microvials pinned below the corresponding specimens.
Photographs were taken using a Canon 7D Mark II digital camera with a Canon macro lens EF 100 mm and MP-E 65 mm for habitus, and an Olympus BX51 microscope for terminalia.Figures were stacked using Helicon Focus v. 5.3 and assembled by Adobe Photoshop 2020.The distribution map was prepared using the online version of SimpleMappr (Shorthouse 2010).Terminology follows Buck and Marshall (2006b) and Lonsdale (2020).Measurements were obtained using a calibrated micrometer; body length is measured from apex of frons to apex of abdomen; interocular space is the width between eyes.
Diagnosis.The subgenus Loxocera can be recognized by the following combination of character states: frontal vitta desclerotized, dull, velvety; lunule sclerotized, broadly exposed between antennal base and anterior margin of frons; fore wing with alula glabrous except margin; hind femur with a subapical patch of microtomentum on ventral surface; male sternite 8 broadly exposed and setulose, fused to tergite 6 and epandrium; female tergite 10 and cerci separated.
Description.Male.Body length 9.0 mm, wing length 7.2 mm, length of antenna 2.5 mm.Generally blackish brown, moderately shining (Fig. 1).Frontal vitta black, with anterior part yellowish brown (Fig. 2); parafacial, gena and posterior eye margin yellowish brown; proboscis and palpus pale brown.Wing slightly infumated, with broad, transverse, dark band at level of posterior crossvein, band more or less interrupted along center of cells r 4+5 and dm (Fig. 1); wing veins yellowish brown to brown.Halter white with base slightly darkened.Legs with trochanters, apical half of fore and mid femora, fore and mid tibiae, basal half of hind tibia, and tarsomere I pale brown.Bristles on head and thorax black.
Head (Figs 1, 2) transverse oblong in dorsal view, largely glabrous; length along midline 0.8 times as long as width across eyes, width across eyes 1.9 times as broad as interocular space.Frons slightly protruding beyond level of anterior eye margin; frontal vitta with shallow depression at middle; frontal orbit with some short, scattered hairs.Ocellar triangle broad, smooth, with silvery tomentose stripes along lateral margins.Face strongly slanting, with weakly elevated median carina.Parafacial narrow, with a tomentose golden patch between anterior eye margin and lunule.Gena swollen; postgena covered with silvery tomentum.Occiput with a large silvery tomentose patch at middle above foramen.Head chaetotaxy: 1 ocellar seta, 1 postvertical seta, 1 inner vertical seta, 1 outer vertical seta.Antenna (Figs 3, 4) long and thick, with short dense setulae; scape nearly as long as pedicel, gradually widened towards apex of segment; first flagellomere about 2.1 times as long as pedicel, apex very weakly curving ventrally; arista laterally compressed and very high, arising at apex of first flagellomere, 1.8 times as long as first flagellomere, divided into small aristomere 1 and large aristomeres 2+3.Palpus elongate oval, with short, dense setulae and long, scattered setae.
Etymology.The specific epithet is dedicated to the Chinese entomologist Chikun Yang , in honor of his excellent contribution to Chinese insect taxonomy.
Comparative notes.This new species is similar to L. (L.) fujiana (Wang, 1999) and L. (L.) maculithorax sp.nov.by sharing the laterally compressed and high arista which arises at the apex of the antennal first flagellomere, and the broad, transverse, dark band on the wing.The new species differs from L. (L.) fujiana by the following character states: head blackish brown with anterior Loxocera (Loxocera) fujiana (Wang, 1999) Terarista fujiana Wang, 1999: 268 (protologue); Wang and Yang (2003:  Diagnosis.Generally blackish brown; face black; antennal scape and pedicel subequal in length; apex of antennal first flagellomere not produced beyond base of arista; arista laterally compressed and very high, arising at apex of antennal first flagellomere and 2 times as long as the latter; wing with broad, transverse, dark band at level of posterior crossvein; segment 8 of female with shallowly emarginated posterodorsal margin and deeply incised posteroventral margin. Distribution.China -Fujian: Wuyishan (Fig. 37).
Remarks.For redescription and photographs of this species, see Zhou et al. (2022).Diagnosis.Generally brown to blackish brown; face yellowish brown; antennal pedicel distinctly longer than scape; antennal first flagellomere about 3 times as long as pedicel, gradually narrowed towards apex; arista whitish yellow, thin, arising near midpoint of antennal first flagellomere and 1.3 times as long as the latter; mesonotum blackish, with irregular brownish margin; wing without transverse dark band; hypandrial lobe large, broad, covered with short setae; pregonite short, simple in shape, apically blunt; phallus shovel-like, relatively long, abruptly widened apically with rounded posterior margin.
Head (Figs 11,12) nearly rounded in dorsal view, largely glabrous; length along midline 0.9 times as long as width across eyes, width across eyes 2 times as broad as interocular space.Frons strongly protruding beyond level of anterior eye margin; frontal vitta with shallow depression at middle; frontal orbit with some short, scattered hairs.Ocellar triangle broad, smooth.Face strongly slanting, with weakly elevated median carina.Parafacial narrow, with a tomentose golden patch between anterior eye margin and lunule.Gena swollen; postgena covered with silvery tomentum.Occiput with a large silvery tomentose patch at middle above foramen.Head chaetotaxy: 1 ocellar seta, 1 postvertical seta, 1 inner vertical seta, 1 outer vertical seta.Antenna (Fig. 12) long and thick, with short dense setulae; pedicel distinctly longer than scape; first flagellomere about 3 times as long as pedicel, gradually narrowed towards apex; arista thin, arising near midpoint of first flagellomere, 1.3 times as long as first flagellomere, divided into small aristomere 1 and large aristomeres 2+3.Palpus elongate oval, with short dense golden setulae and long scattered black setae.
Etymology.The specific epithet is dedicated to the Canadian entomologist Owen Lonsdale (Agriculture and Agri-Food Canada, Ottawa, Canada), for his outstanding contribution to the systematics of Acalyptratae, and his encouragement to the first author.
Comparative notes.This new species is most similar to L. (L.) omei Shatalkin, 1998, but it can be easily distinguished from the latter by the following character states: antennal pedicel distinctly longer than scape [vs subequal in length in L. (L.) omei]; antennal first flagellomere distinctly narrowed towards apex [vs weakly narrowed in L. (L.) omei]; mesonotum largely blackish with irregular brownish margin [vs uniformly blackish in L. (L.) omei]; abdomen yellowish brown with distinct ring-like markings [vs blackish brown with apical segments reddish in L. (L.) omei].
Antennal morphology similar to that of this new species also presents in L. (L.) hoffmannseggi Meigen, 1826 from Central and West Europe and L. (L.) matsumurai Iwasa, 1992 from Japan.However, the coloration of head, thorax, and abdomen of the new species is very different from that of the latter two species.Additionally, the head of the new species is nearly rounded in dorsal view with the frons strongly protruding anteriorly, while in the latter two species, the head is transverse oblong in dorsal view and the frons weakly protrudes anteriorly.   of arista; arista laterally compressed and very high, arising at apex of antennal first flagellomere and 2.1 times as long as the latter; mesonotum blackish, with irregular, brownish margin; wing with broad, transverse, dark band at level of posterior crossvein; hypandrial lobe large, short, covered with long setae; pregonite stout, lobate, apically blunt, with some rounded processes; phallus tongue-like, relatively short, with rounded posterior margin.
Head (Figs 20,21) transverse oblong in dorsal view, largely glabrous; length along midline 0.7 times as long as width across eyes, width across eyes 2 times as broad as interocular space.Frons slightly protruding beyond level of anterior eye margin; frontal vitta with shallow depression at middle; frontal orbit with some short, scattered hairs.Ocellar triangle broad, smooth, with silvery tomentose stripes along lateral margins.Face strongly slanting, with moderately elevated median carina.Parafacial narrow, with a tomentose golden patch between anterior eye margin and lunule.Gena swollen; postgena covered with silvery tomentum.Occiput with a large silvery tomentose patch at middle above foramen.Head chaetotaxy: 1 ocellar seta, 1 postvertical seta, 1 inner vertical seta, 1 outer vertical seta.Antenna (Fig. 21) long and thick, with short, dense setulae; scape nearly as long as pedicel, gradually widened towards apex; first flagellomere about 2 times as long as pedicel, apex strongly curving ventrally, produced beyond base of arista; arista laterally compressed and very high, arising at apex of first flagellomere, 2.1 times as long as first flagellomere, divided into small aristomere 1 and large aristomeres 2+3.Palpus elongate oval, with short, dense setulae and long, scattered setae.
Etymology.The specific epithet is derived from Latin macula (meaning spotted) and Greek thorax (meaning thorax), referring to the mesonotum of the new species, which is blackish with an irregular brownish margin.
Diagnosis.Generally dark brown; face blackish; antennal scape distinctly longer than pedicel; antennal first flagellomere stick-like, weakly narrowed towards apex of segment; arista whitish yellow, thin, arising before midpoint of antennal first flagellomere and 1.4 times as long as the latter; wing without transverse dark band; hypandrial lobe very large, broad, covered with short, sparse setae on inner surface; pregonite rather long, slender, curved apically with sharp apex; phallus droplet-like, elongate, abruptly narrowed apically.
Head (Figs 28,29) nearly rounded in dorsal view, largely glabrous; length along midline nearly as long as width across eyes, width across eyes 2 times as broad as interocular space.Frons strongly protruding beyond level of anterior eye margin; frontal vitta with shallow depression at middle; frontal orbit with some short, scattered hairs.Ocellar triangle broad, smooth.Face strongly slanting, with moderately elevated median carina.Parafacial narrow, with a tomentose golden patch between anterior eye margin and lunule.Gena swollen; postgena covered with silvery tomentum.Occiput with a large silvery tomentose patch at middle above foramen.Head chaetotaxy: 1 ocellar seta, 1 postvertical seta, 1 inner vertical seta 1 outer vertical seta.Antenna (Fig. 29) long, relatively slender, with short, dense setulae; scape distinctly longer than pedicel; first flagellomere about 4.6 times as long as pedicel, stick-like, laterally compressed, weakly narrowed towards apex; arista thin, arising before midpoint of first flagellomere, 1.4 times as long as first flagellomere, divided into small aristomere 1 and large aristomeres 2+3.Palpus elongate oval, with short, dense, white setulae.
Female.Unknown.Etymology.The specific epithet is derived from Latin obscura (meaning dark, indistinct), referring to the dark-brown body color of the new species.
Remarks.This species was described based on one male (the holotype) from Sichuan, China (Shatalkin 1998).The habitus photographs of the holotype (Figs 35,36) are provided here for facilitating the identification of this species.
Distribution.China -Hubei: Shennongjia.Remarks.Loxocera anulata was originally described as a member of the subgenus Loxocera based on one male (the holotype) from Hubei, China (Wang and Yang 1998a).The specific epithet of this species was spelled as anulata in its original description, where the authors (Wang and Yang 1998a) intend to create the name from the Latin adjective anulatus, -a, -um (meaning ringed, referring to the annulations on the abdomen of this species), therefore it is considered as the correct original spelling.The subsequent usage of the specific epithet annulata (Buck and Marshall 2006b) is treated as an incorrect subsequent spelling.Buck and Marshall (2006b) failed to assign this species (as L. annulata) to a certain subgenus based on its brief original description.This species was catalogued by Tang et al. (2021) without subgeneric placement.
The holotype of L. anulata was examined during the present study.It satisfied the diagnosis of Loxocera s. lat.provided by Buck and Marshall (2006b).The sclerotized and sub-shining frontal vitta, the hiding lunule, the microtrichose on the alula, and the very reduced and bare male sternite 8 match the characters used to diagnose the subgenus Imantimyia Frey, 1925 (Buck andMarshall 2006b).Therefore, this species is herein transferred to Imantimyia.Loxocera tianmuensis Wang and Yang 1998b: 200, 201 (protologue); Buck and Marshall (2006b: 199) (listed, distribution).Holotype (♂): China, Zhejiang, Xitianmushan, CAU.Remarks.Loxocera tianmuensis was originally described based on one male (the holotype) from Zhejiang, China (Wang and Yang 1998b), but the authors did not assign it to any subgenus.Buck and Marshall (2006b) mentioned that this species "cannot be confidently placed to subgenus" due to the inadequate original description.No new information has since been published on this species.
The holotype of L. tianmuensis was examined in the course of the present study.The date on the collection data label of the holotype does not match that in the original description.The authors (Wang and Yang 1998b) communicated personally with the specimen collector during the preparation of the manuscript, thus providing a precise date of specimen collection in the original L. (L.) lonsdalei sp.nov.which has been collected from four localities in central China.Considering the diversity presented from so few specimens, it is very likely that many more undescribed species will be found given additional collecting.

Figure 37 .
Figure 37. Known distribution of species of the subgenus Loxocera in China.