﻿First and second instar larvae and adults of a new Homidia species (Collembola, Entomobryidae) recorded from Xizang Autonomous Region with three new records

﻿Abstract Three new recorded species of genus Homidia were collected from Xizang Autonomous Region, China, in the present paper. Among them, a new species, Homidiabreviseta Pan, sp. nov., is included in the present paper. This new species can be identified by having a single uninterrupted dark band on central thoracic segment III; 14 macrochaetae on abdominal segment I and seven on the posterior central abdominal segment IV (half segment); and very short bothriotricha on abdominal segments II–IV. It can be easily discriminated from similar species of Homidia by its colour pattern, chaetotaxy of the labium, and abdominal segments I and IV. The chaetotaxy of the first and second instar larvae of this new species and a key to four species of genus Homidia from Xizang are also provided.


Introduction
The genus Homidia Börner, 1906 is collembolan taxon widely distributed in southeast China and is generally found in every habitat, such as in leaf litter of forest, farmland, vegetable field, residential area and so on. This genus was established as a subgenus of Entomobrya (Rondani, 1861) by Börner (1906) and later raised to the generic level by Denis (1929). The significant character for the identification is that the dens bears spines and abdominal segment IV has an anterior series of macrochaetae transversely arranged as "eyebrows" in adults. Also, individuals with transverse bands, spots, or without pigment on the dorsal body are distinctive. Homidia species are good at jumping and large enough to be seen in wild by the naked eye. To date, 74 species of this genus have been reported worldwide (Bellinger et al. 1996(Bellinger et al. -2021, and 42 are recorded from China (Ma and Pan 2017;Zhuo et al. 2018;Pan and Yang 2019;Pan and Ma 2021). However, among them only one species, Homidia tibetensis Chen & Zhong, 1998, was reported from Xizang.
Lhasa is the administrative centre of Xizang Autonomous Region, and with an altitude around 3600 m, it is one of the highest altitude cities in the world. Annual sunshine averages 3000 h and rainfall 200-510 mm. The climatic conditions results in unique biodiversity, including among Collembola. In order to gather more information about the diversity of Collembola from this region, we spent several days collecting around Lhasa in August 2019. Among the collected material, we found two new records and one new species of the genus Homidia. The chaetotaxy of the adult as well as the first and second instar larvae of the new species is described in detail. A comparison of the new species with the most similar species of the genus Homidia is provided. A checklist of all Homidia species found from Xizang is included as well as a key to separate them.

Materials and methods
Collembolan individuals were sieved from leaf litter in the field, collected with an aspirator, and stored in 99% ethanol at -20 C in the laboratory. Specimens were photographed using a Nikon DS-Fi1 camera mounted onto a Nikon SMZ1000 stereomicroscope, then cleared in lactic acid, mounted in Hoyer's medium under a coverslip, and examined with a Nikon 80i phase-contrast microscope. Lengths of morphological structures were measured from specimens in ethanol by NIS-Elements 3.1 software. Photographs, illustrations, and labels were enhanced by Photoshop CS5 (Abode Systems).
Specimens and all types are deposited in the School of Life Sciences, Taizhou University (TZU).

Taxonomic account
Fourteen samples (4687-4700) were collected in total from Lhasa from 1-VIII-2019 to 8-VIII-2019. The collection included two new records and one new species of the genus Homidia: Homidia sichuanensis Jia et al., 2010, Homidia sinensis Denis, 1929. A fourth species, Homidia tibetensis Chen & Zhong, 1998 (Fig. 3), which had been recorded from Xizang in a previous study (Chen and Zhong 1998), was absent from the present sampling. The sampling information of three Homidia species recorded here are listed in Table 1. Homidia sichuanensis was described by Jia et al. (2010) from Sichuan Province, China, and is identified by its colour pattern and the presence of mac p4 and A6-A10 on Th. III and Abd. IV, respectively. It is widely distributed in western China, from Sichuan Province to Guangxi Zhuang Autonomous Region (recorded in our collection S09022603). Homidia sinensis was reported by Denis (1929) from Foochow, Fujiang Provnice, China, and is distinct from other species of Homidia by its colour pattern, chaetotaxy of the labium and Abd. I, III, and IV. It has a wide distribution, and we found it in most regions of China. Homidia tibetensis was described by Chen and Zhong (1998) from Xizang and is only know from there, but the detailed collecting information is not provided in the original description. This species, which is well-characterized morphologically by its colour pattern and chaetotaxy, is not included in our collections.
Key to the Homidia species from Xizang Paratypes. 7♀adults, 1 first and 1 second instar larva on slides and 5 adults in ethanol, same data as holotype.

Descriptions of adults.
Size. Body length up to 1.62 mm. Colour pattern. Ground colour yellow-white in ethanol. Eye patches dark blue. Antennae gradually darker from Ant. I to Ant. IV. A dark narrow transverse band between basal antennae. Lateral Th. II-III with longitudinal bands, and dorsal Th. III with central transverse uninterrupted dark band. Coxa with dark pigment. Dorsal Abd. II and Abd. IV with central irregular dark bands. Dorsal Abd. III and Abd. V from anterior to posterior margin with dark transverse bands, and Abd. III with two lateral unpigmented areas. Dorsal Abd. IV with two middle and posterior transverse bands, the central one interrupted by a middle line (Figs 4,5). Ventral side of body and VT pale white, without pigment (Fig. 6). Subadults with the same colour pattern as adults, but paler (Fig. 7).
Description of the second instar larva. Colour pattern. Ground colour whitish; eye patches dark blue. The colour pattern of the second instar larva is similar to adult, but slighter.
The chaetotaxy of the second instar larva is more complex than first instar, and several primary chaetae with secondary chaetae present in the second instar (Figs 43-54). The detailed comparison between these two instars are tabulated in Table 3.
Ecology. All stages were found in leaf litter of the Family Rosaceae.
Etymology. The specific epithet refers to the very short chaeta bothriotricha on dorsal Abd. II-IV (brevi and seta).
Remarks. This new species is mostly similar to Homidia similis Szeptycki, 1973 in having Th. III, Abd. III, and the middle and posterior of Abd. IV and Abd. V with transverse bands; in the chaetotaxy of the labium, head, Th. III, and Abd. II-III; and smooth chaetae on posterior face (five) and lateral flap (six) of VT. However, the new species can be differentiated from H. similis by the uninterrupted band on Th. III (interrupted by a central line in latter), a broad band from the anterior to posterior margin of Abd. III (anterior margin not pigmented in the latter), 14 mac on Abd. I (nine in the latter), and seven posterior central mac on Abd. IV (eight in the latter). Also, the new species is similar to H. bilineata Lee & Park, 1984 and Homidia huashanensis Jia et al., 2005 in having mac on the dorsal head, Th. II-III, and Abd. II and chaetal formula on labium; however, they can be discriminated by colour pattern, chaetotaxy on Abd. I and posterior central Abd. IV. A detailed comparison of these four similar species is given in Table 2.    Szeptycki (1973), † Refers to the description by Jordana (2012), ‡ Refers to the description by Chen et al. (2011). This species is the second species of genus Homidia described from Xizang, and it can be easily distinguished from the first new species recorded from this region (H. tibetensis Chen & Zhong, 1998)