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Research Article
Two new species and two new records of Homidia (Collembola, Entomobryidae) from China
expand article infoMei-dong Jing‡, Yi-tong Ma‡
‡ Nantong University, Nantong, China

Corresponding author: Yi-tong Ma ( mayitong@ntu.edu.cn )

Academic editor: Louis Deharveng
© 2022 Mei-dong Jing, Yi-tong Ma.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Jing M-d, Ma Y-t (2022) Two new species and two new records of Homidia (Collembola, Entomobryidae) from China. ZooKeys 1135: 181-212. https://doi.org/10.3897/zookeys.1135.89373
ZooBank: urn:lsid:zoobank.org:pub:18798B62-4F1F-4026-91F1-D773E0176082
Open Access

Abstract

Homidia, one of the largest genera of the family Entomobryidae, is widely distributed in China. To date, 46 species of this genus are present in China and account for approximately 60 % of all known species of the genus. In the present paper, two new species of Homidia are described from China: H. acutus sp. nov. and H. changensis sp. nov. The former is discriminated by the brown to blue-violet pigment present on whole dorsal body and by pointed tenent hairs. The latter is characterised by having only scattered traces of brown pigment on tergites, and by the special macrochaetal formula of coxae. Additionally, two known species of the genus, H. linhaiensis Shi, Pan & Qi, 2009 and H. socia Denis, 1929, are reported from Jiangxi Province for the first time, and some of their taxonomic characters are described. A key to the Chinese species of the genus is provided.

Keywords

Chaetotaxy, Entomobryinae, Jiangxi, taxonomy

Introduction

Homidia was established as a subgenus of Entomobrya by Börner (1906) based on the presence of inner spines at the base of the dens in adults. Denis (1929) considered the character significant enough to raise Homidia to generic level. The genus is also characterised by the presence of “eyebrow” macrochaetae on the anterior part of Abd. IV in adults, the absence of scales, and a bidentate mucro with the subapical tooth much larger than the apical one.

Colour pattern plays a key role in classification of Homidia because intraspecific variability is very low. However, some species, such as H. sauteri, H. similis, H. sinensis, and H. socia, are widespread and some intraspecific variability of colour pattern from different regions may be sometimes present. Chaetotaxy is also very useful in species identification, especially that of Abd. I, IV, and labium basis.

The first person to study the Chinese Homidia was the Frenchman J. R. Denis, who reported Homidia sauteri (Börner, 1909) from Yunnan Province in 1928. To date, 46 species have been described or reported from China among a total of 75 species worldwide (Bellinger et al. 1996–2022, Table 1). These species are mainly distributed in the eastern region of China, especially Zhejiang Province (Fig. 1).

Table 1.
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Species checklist of Homidia recorded from China.

Species name Distribution
H. acutus sp. nov. Jiangxi*
H. anhuiensis Li & Chen, 1997 Anhui
H. apigmenta Shi, Pan & Zhang, 2010 Fujian
H. breviseta Pan, 2022 Xizang
H. changensis sp. nov. Jiangxi*
H. chroma Pan & Yang, 2019 Guangdong
H. dianbaiensis (Lin, 1985) Guangdong
H. emeiensis Jia, Chen & Christiansen, 2004 Sichuan
H. fascia Wang & Chen, 2001 Jiangsu
H. formosana Uchida, 1943 Taiwan; Zhejiang
H. hangzhouensis Pan & Ma, 2021 Zhejiang
H. hexaseta Pan, Shi & Zhang, 2011 Zhejiang
H. huashanensis Jia, Chen & Christiansen, 2005 Shaanxi
H. jordanai Pan, Shi & Zhang, 2011 Zhejiang
H. laha Christiansen & Bellinger, 1992 Zhejiang
H. latifolia Chen & Li, 1999 Zhejiang
H. leei Chen & Li, 1997 Jiangxi
H. leniseta Pan & Yang, 2019 Guangdong
H. linhaiensis Shi, Pan & Qi, 2009 Jiangxi*; Zhejiang
H. maijiensis Zhou & Ma, 2022 Gansu
H. mediofascia Shi, Pan & Bai, 2009 Shaanxi
H. nigrifascia Ma & Pan, 2017 Guizhou
H. nigrocephala Uchida, 1943 Taiwan
H. obliquistria Ma & Pan, 2017 Guizhou
H. pentachaeta Li & Christiansen, 1997 Jiangsu
H. phjongjangica Szeptycki, 1973 Jilin; Zhejiang
H. polyseta Chen, 1998 Hunan
H. pseudofascia Pan, Zhang & Li, 2015 Jiangsu
H. pseudosinensis Shi & Pan, 2012 Fujian
H. qimenensis Yi & Chen, 1999 Anhui; Fujian; Guangxi; Jiangxi; Zhejiang
H. quadriseta Pan, 2018 Zhejiang
H. quadrimaculata Pan, 2015 Zhejiang
H. sauteri (Börner, 1909) Shanxi; Yunnan; Zhejiang
H. sichuanensis Jia, Zhang & Jordana, 2010 Sichuan; Guangdong; Guangxi; Guizhou; Xizang
H. similis Szeptycki, 1973 Zhejiang
H. sinensis Denis, 1929 Beijing; Fujian; Yunnan; Zhejiang; Xizang
H. socia Denis, 1929 Anhui; Fujian; Guangxi; Jiangsu; Jiangxi*; Taiwan; Zhejiang
H. taibaiensis Yuan & Pan, 2013 Shaanxi
H. tiantaiensis Chen & Lin, 1998 Zhejiang
H. tibetensis Chen & Zhong, 1998 Xizang
H. transitoria Denis, 1929 Fujian
H. triangulimacula Pan & Shi, 2015 Zhejiang
H. unichaeta Pan, Shi & Zhang, 2010 Zhejiang
H. wanensis Pan & Ma, 2021 Anhui
H. xianjuensis Wu & Pan, 2016 Zhejiang
H. yandangensis Pan, 2015 Zhejiang
H. zhangi Pan & Shi, 2012 Zhejiang
H. ziguiensis Jia, Chen & Christiansen, 2003 Hubei

Notes:* described or reported in this paper.
Figure 1. 

Distribution of all Chinese species of Homidia (the number in each region represents the number of the species reported from this province). Scale bar: 1000 km.

Materials and methods

Specimens were collected with an aspirator and stored in 99 % alcohol. They were mounted on glass slides in Marc André II solution, and were studied with a Leica DM2500 phase contrast microscope. Photographs were taken with a Leica DFC300 FX digital camera mounted on the microscope and a ZEISS Gemini SEM 300. They were enhanced with Photoshop CS2 (Adobe Inc.). The nomenclature of the dorsal macrochaetotaxy of head and interocular chaetae are described following Szeptycki (1973) and Mari Mutt (1986). Labial chaetae are designated following Gisin (1964) and tergal chaetae of the body after Szeptycki (1979).

Abbreviations

Abd abdominal segment;

Ant antennal segment;

asl above sea level;

mac macrochaeta(e);

ms specialised microchaeta(e);

NTU Nantong University;

sens specialised ordinary chaeta(e);

Th thoracic segment.

Taxonomic account

Homidia acutus sp. nov.

https://zoobank.org/C2B263A9-3D3D-4BEE-A1AF-2B04559281E6
Figs 2–5, 6–13, 14–20, 21–29, 30, 31, 32, 33, 34–40, Table 2

Type material

Holotype. 1♀ on slide, China, Jiangxi Province, Pingxiang City, Luxi County, Gate of Wugong Mountain, 27°29'27"N, 114°07'33"E, 393 m asl, sample number 1229, collected by Y-T Ma, 7-XI-2020, deposited in NTU. Paratypes. 3♀ on slides, same data as holotype.

Descriptions

Size. Body length up to 2.05 mm.

Colouration. Ground colour pale white to pale yellow. Eye patches dark blue. Brown to blue-violet pigment present on whole dorsal body, antennae, legs, ventral tube, and manubrium. Some unpigmented irregular stripes or spots present on dorsal side of body (Figs 2–5).

Figures 2–5. 

Habitus of Homidia acutus sp. nov. 2 lateral view 3, 4 dorsal view 5 ventral view. Scale bars: 500 μm.

Head. Antenna 0.46–0.58× body length; antennal segment ratio I: II: III: IV = 1: 1.35–1.67: 1.20–1.33: 1.88–1.93. Apical bulb of Ant. IV bilobed (Fig. 6). Ant. III organ with two rod-like chaetae (Fig. 7). Ant. II with three distal rod-like chaetae (Fig. 8). Eyes 8 + 8, G and H smaller than others; interocular chaetae with p, r, and t. Dorsal cephalic chaetotaxy with three antennal (A), three ocellar (O) and five sutural (S) mac (Fig. 9). Labral chaetae as 4/5, 5, 4, all smooth; labral papillae absent (Fig. 10). Basal chaeta of maxillary outer lobe thin, subequal to apical one; sublobal plate with three smooth chaeta-like processes (Fig. 11). Lateral process (l.p.) of labial papilla E differentiated, as thick as normal chaeta, with tip almost reaching apex of papilla E (Fig. 12). Chaetal formula of labial base as MRel1L2, chaetae e and l1 smooth, others ciliate, M of one side smooth in one individual, R/M as 0.45–0.60 (Fig. 13).

Figures 6–13. 

Homidia acutus sp. nov. 6 apex of Ant. IV 7 Ant. III organ 8 distal Ant. II 9 dorsal chaetotaxy of head 10 labrum 11 maxillary palp and outer lobe 12 labial palp E 13 labial base. Scale bars: 20 μm.

Thorax. Th. II with four medio-medial (m1, m2, m2i, m2i2), three medio-sublateral (m4, m4i, m4p), 35–38 posterior mac, one ms and two sens (ms antero-internal to sens). Th. III with 40–49 mac and two sens (Fig. 14). Pseudopores on coxae not clearly seen; coxal macrochaetal formula as 4/4+1, 3/4+2 (Figs 15–17). Trochanteral organ with 40 smooth chaetae (Fig. 18). All tenent hairs pointed and shorter than inner edge of unguis. Unguis with three inner teeth, basal pair located at 0.39–0.42 distance from base of inner edge of unguis, distal unpaired tooth at 0.64–0.70 distance from base; unguiculus lanceolate, outer edge slightly serrate (Figs 19–31).

Figures 14–20. 

Homidia acutus sp. nov. 14 cchaetotaxy of Th. II–III 15–17 coxal chaetotaxy of fore, middle and hind leg 18 trochanteral organ 19, 20 fore and hind foot complex. Scale bar: 50 μm (14); 20 μm (15–20).

Figures 21–29. 

SEM photomicrographs of Homidia acutus sp. nov. 21, 23, 25 fore foot complex of three individuals 22, 24, 26 magnifications of white rectangles of 21, 23, 25 respectively 27, 29 middle foot complex of two individuals 28 magnification of white rectangle of 27. Scale bars: 20 μm.

Figures 30, 31. 

SEM photomicrographs of Homidia acutus sp. nov. 30 hind foot complex 31 magnification of white rectangle of 30. Scale bars: 20 μm.

Abdomen. Range of Abd. IV length as 5.00–7.50× as dorsal axial length of Abd. III. Abd. I with 11 or 12 (a1a, a1–3, a5, m2–4, m2i, m4i, m4p, a1i sometimes present) mac, ms antero-external to sens. Abd. II with six (a2, a3, m3, m3e, m3ea, m3ep) central, one (m5) lateral mac and two sens. Abd. III with two (a2, m3) central and four (am6, pm6, m7a, p6) lateral mac, one ms and two sens (Fig. 32). Abd. IV with two normal sens and approximately half length of elongate sens; anteriorly with six mac arranged in irregular transverse row, posteriorly with five central mac (A5, A6, B5, B6, Ae7), laterally with 12 or 13 mac (Fig. 33). Abd. V with three sens, middle one posterior to m3 (Fig. 34). Anterior face of ventral tube with 27–32 ciliate chaetae, 3+3 of them as mac, line connecting proximal (Pr) and external-distal (Ed) mac oblique to median furrow (Fig. 35); posterior face with six distal smooth and numerous ciliate chaetae; lateral flap with seven smooth and 10–15 ciliate chaetae (Fig. 36). Manubrial plate dorsally with 13–15 ciliate chaetae and three pseudopores (Fig. 37); ventrally with 32–38 ciliate chaetae on each side (Fig. 38). Dens with 32–59 smooth inner spines (Fig. 39). Mucro bidentate with subapical tooth larger than apical one; tip of basal spine reaching apex of subapical tooth; distal smooth section of dens almost equal to mucro in length (Fig. 40).

Figure 32. 

Chaetotaxy of Abd. I–III of Homidia acutus sp. nov. Scale bar: 50 μm.

Figure 33. 

Chaetotaxy of Abd. IV of Homidia acutus sp. nov. Scale bar: 50 μm.

Figures 34–40. 

Homidia acutus sp. nov. 34 chaetotaxy of Abd. V 35 anterior face of ventral tube 36 posterior face and lateral flap of ventral tube 37 manubrial plaque 38 ventro-apical part of manubrium 39 proximal section of dens (circles also representing spines) 40 mucro. Scale bars: 20 μm.

Ecology

In the leaves litter of Phyllostachys edulis.

The name of the species is derived from the Latin acutus = pointed, which refers to the tip of tenent hairs.

Remarks

The new species is characterised by pointed tip of tenent hairs and this character can be used to distinguish it from all known species of Homidia. It is similar to H. zhangi Pan & Shi, 2012 in colour pattern and labium, but there are some differences between them, such as tenent hairs, posterior chaetotaxy of Abd. IV, and other characters. The detailed character comparisons are listed in Table 2.

Table 2.
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Comparison between H. acutus sp. nov. and H. zhangi.

Characters H. acutus sp. nov. H. zhangi
Tip of tenent hairs pointed clavate
Mac m5 on Th. II present absent
Centro-posterior mac on Abd. IV 5 (A5, A6, B5, B6, Ae7) 3(4) (A6, B6, Ae7. B5 sometimes absent)
Inner teeth on unguis 3 4
Relative position of ms to sens on Abd. I antero-external antero-internal
Relative position of middle sens to m3 on Abd. V postero-external antero-external

Homidia changensis sp. nov.

https://zoobank.org/7A88BCD3-07D5-40B4-8E44-BE1F21AD6FC8
Figs 41–42, 43–49, 50–55, 56, 57, 58–64, Table 3

Type material

Holotype. 1♀ on slide, China, Jiangxi Province, Nanchang City, Xinjian District, Jiuxi, 28°47'56"N, 115°45'11"E, 168 m asl, sample number 1243, collected by Y-T Ma, 12-XI-2020, deposited in NTU. Paratypes. 2♀ on slides, same data as holotype.

Description

Size. Body length up to 2.33 mm.

Colouration. Ground colour yellow. Ant. II–IV and distal part of Ant. I brown. Eye patches dark blue. Coxae, tibiotarsi, posterior part of Abd. IV and Abd. V with scattered brown pigment (Figs 41, 42).

Figures 41, 42. 

Habitus of Homidia changensis sp. nov. Scale bars: 500 μm.

Head. Antenna 0.50–0.57× body length; antennal segment ratio I: II: III: IV = 1: 1.33–1.50: 1.17–1.30: 1.90–2.00. Apical bulb of Ant. IV bilobed (Fig. 43). Ant. III organ with two rod-like chaetae (Fig. 44). Ant. II with four distal rod-like chaetae (Fig. 45). Eyes 8 + 8, G and H smaller than others; interocular chaetae with p, r, and t. Dorsal cephalic chaetotaxy with three antennal (A), three ocellar (O) and five sutural (S) mac (Fig. 46). Basal chaeta of maxillary outer lobe thin, subequal to apical one; sublobal plate with three smooth chaeta-like processes (Fig. 47). Lateral process (l.p.) of labial papilla E differentiated, as thick as normal chaeta, with tip almost reaching apex of papilla E (Fig. 48). Chaetal formula of labial base as M1M2ReL1L2, chaeta e smooth, others ciliate, R/M1 as 0.63–0.70 (Fig. 49).

Figures 43–49. 

Homidia changensis sp. nov. 43 apex of Ant. IV 44 Ant. III organ 45 distal Ant. II 46 dorsal chaetotaxy of head 47 maxillary palp and outer lobe 48 labial palp E 49 labial base. Scale bars: 20 μm.

Thorax . Th. II with four medio-medial (m1, m2, m2i, m2i2), three medio-sublateral (m4, m4i, m4p), 32–38 posterior mac, one ms and two sens (ms antero-internal to sens). Th. III with 38–47 mac and two sens (Fig. 50). Pseudopores on coxa I–III as 2, 3, 2, respectively; coxal macrochaetal formula as 3/4+3(4), 3/4+2 (Figs 51–53). Trochanteral organ with 45–48 smooth chaetae (Fig. 54). Tenent hairs clavate and almost equal to inner edge of unguis. Unguis with four inner teeth, basal pair located at 0.31–0.41 distance from base of inner edge of unguis, distal unpaired teeth at 0.63–0.71 and 0.83–0.84 distance from base; unguiculus lanceolate, outer edge slightly serrate (Fig. 55).

Figures 50–55. 

Homidia changensis sp. nov. 50 chaetotaxy of Th. II–III 51–53 coxal chaetotaxy of fore, middle and hind leg 54 trochanteral organ 55 hind foot complex. Scale bar: 50 μm (50); 20 μm (51–55).

Abdomen . Range of Abd. IV length as 6.03–10.40× as dorsal axial length of Abd. III. Abd. I with 11 (a1a, a1–3, a5, m2–4, m2i, m4i, m4p) mac, ms antero-external to sens. Abd. II with six (a2, a3, m3, m3e, m3ea, m3ep) central, one (m5) lateral mac and two sens. Abd. III with two (a2, m3) central and four (am6, pm6, m7a, p6) lateral mac, one ms and two sens (Fig. 56). Abd. IV with two normal sens; anteriorly with six or seven mac arranged in irregular transverse row, posteriorly with 5–7 (A4, A6, B4–6, A5 and Ae7 sometimes present) central mac, laterally with 20–22 mac (Fig. 57). Abd. V with three sens, middle one posterior to m3 (Fig. 58). Anterior face of ventral tube with 24–27 ciliate chaetae, 3+3 of them as mac, line connecting proximal (Pr) and external-distal (Ed) mac oblique to median furrow (Fig. 59); posterior face with two or four distal smooth and numerous ciliate chaetae; lateral flap with six smooth and 14–16 ciliate chaetae (Fig. 60). Manubrial plaque dorsally with 11 or 12 ciliate chaetae and 2–4 pseudopores (Fig. 61); ventrally with 25–28 ciliate chaetae on each side (Fig. 62). Dens with 16–28 smooth inner spines (Fig. 63). Mucro bidentate with subapical tooth larger than apical one; tip of basal spine reaching apex of subapical tooth; distal smooth section of dens shorter than mucro in length (Fig. 64).

Figure 56. 

Chaetotaxy of Abd. I–III of Homidia changensis sp. nov. Scale bar: 50 μm.

Figure 57. 

Chaetotaxy of Abd. IV of Homidia changensis sp. nov. Scale bar: 50 μm.

Figures 58–64. 

Homidia changensis sp. nov. 58 chaetotaxy of Abd. V 59 anterior face of ventral tube 60 posterior face and lateral flap of ventral tube 61 manubrial plaque (a circle with a slash means a pseudopore) 62 ventro-apical part of manubrium 63 proximal section of dens (circles also representing spines) 64 mucro. Scale bars: 20 μm.

Ecology

In the leaves litter of Phyllostachys edulis.

Etymology

Named after its locality: Nanchang City, which is abbreviated as Chang.

Remarks

The new species is characterised by its colour pattern and coxal macrochaetotaxy, and can be easily distinguished from all known species of Homidia. It is similar to the Chinese species H. huashanensis Jia, Chen & Christiansen, 2005, H. jordanai Pan, Shi & Zhang, 2011, and H. unichaeta Pan, Shi & Zhang, 2010 and the Korean species H. koreana Lee & Lee, 1981 in colour pattern, but significant differences exist between these species, such as chaetotaxy on Abd. I and IV and number of dental spines (Table 3).

Table 3.
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Comparison between H. changensis sp. nov. and similar species.

Characters H. changensis sp. nov. H. huashanensis H. jordanai H. unichaeta H. koreana
Ground colour yellow hazel pale yellow pale to yellowish brown
Length ratio of antenna to body 0.50–0.57 0.67 1.00 0.80–1.00 unknown
Chaetal formula of labial base M1M2ReL1L2 MRE(e)L1L2 MReL1L2 MRel1L2 MReL1L2
Chaetae a1, a1a on Abd. I present present absent a1 rarely present, a1a absent absent
Central mac on Abd. III 2 2 1 2 2
Centro-posterior mac on Abd. IV 5–7 7–9 2(3) 1 6
Dental spines 16–28 80–114 20–40 19–23 40–50

Homidia linhaiensis Shi, Pan & Qi, 2009

Figs 65–66, 67, 68, 69, 70–75

Homidia linhaiensis Shi, Pan & Qi, 2009: 63.

Examined specimens

2♀ on slides, China, Jiangxi Province, Pingxiang City, Luxi Town, Shankouyan Park, 27°36'55"N, 114°01'39"E, 144 m asl, sample number 1231, collected by Y-T Ma, 7-XI-2020, in the rotten leaves of Salix babylonica; 5♀ on slides, China, Jiangxi Province, Nanchang City, Xinjian District, Shizifeng Park, 28°48'48"N, 115°43'15"E, 193 m asl, sample number 1241, collected by Y-T Ma, 12-XI-2020, in the leaves litter of Phyllostachys edulis; 2♀ on slides, China, Jiangxi Province, Shangrao City, Yunbifeng Park, 28°27'47"N, 117°58'55"E, 101 m asl, sample number 1246, collected by Y-T Ma, 14-XI-2020, in the leaves litter of Phyllostachys edulis.

Description

Size. Body length up to 2.00 mm.

Colouration. Ground colour yellow. Ant. III & IV with scattered blue pigment. Eye patches dark blue. Th. III with a pair of dark blue spots and coxae and lateral of Th. II also with blue pigment (Figs 65, 66).

Figures 65, 66. 

Habitus of Homidia linhaiensis. Scale bars: 500 μm.

Head. Antenna 0.44–0.59× body length; antennal segment ratio I: II: III: IV = 1: 1.30–1.47: 1.21–1.33: 2.13–2.51. Eyes 8 + 8, interocular chaetae with p, r, and t. Dorsal cephalic chaetotaxy with three antennal (A), three ocellar (O) and six sutural (S) mac (Fig. 67). Chaetal formula of labial base as MRel1L2, chaetae e and l1 smooth, others ciliate, R/M as 0.56.

Figures 67, 68. 

Homidia linhaiensis 67 dorsal chaetotaxy of head 68 chaetotaxy of Th. II–III. Scale bars: 20 μm (67); 50 μm (68).

Thorax. Th. II with four medio-medial (m1, m2, m2i, m2i2), four medio-sublateral (m4, m4i, m4p, m4pi), 33 posterior mac. Th. III with 36–39 mac and two sens (Fig. 68).

Abdomen. Range of Abd. IV length as 6.28–9.32× as dorsal axial length of Abd. III. Abd. I with 10 (a2, a3, a5, m2–5, m2i, m4i, m4p) mac, ms antero-internal to sens. Abd. II with six (a2, a3, m3, m3e, m3ea, m3ep) central, one (m5) lateral mac and two sens. Abd. III with two (a2, m3) central and five (am6, pm6, m7a, p6, p7) lateral mac, one ms and two sens. Abd. IV anteriorly with 9–13 mac arranged in irregular transverse row, A2 always present and anterior to transverse row; posteriorly with 10–16 central mac, laterally with 23–27 mac (Fig. 69). Anterior face of ventral tube with 24–28 ciliate chaetae, 3+3 of them as mac, line connecting proximal (Pr) and external-distal (Ed) mac oblique to median furrow (Fig. 70); posterior face with four distal smooth and numerous ciliate chaetae (Fig. 71). Manubrial plaque dorsally with 14–17 ciliate chaetae and three pseudopores (Fig. 72); ventrally with 37 ciliate chaetae on each side (Fig. 73). Dens with 12–21 smooth inner spines (Fig. 74). Mucro bidentate with subapical tooth larger than apical one; tip of basal spine reaching apex of subapical tooth; distal smooth section of dens almost equal to than mucro in length (Fig. 75).

Figure 69. 

Chaetotaxy of Abd. IV of Homidia linhaiensis. Scale bar: 50 μm.

Figures 70–75. 

Homidia linhaiensis 70 anterior face of ventral tube 71 posterior face of ventral tube 72 manubrial plaque 73 ventro-apical part of manubrium 74 proximal section of dens (circles also representing spines) 75 mucro. Scale bars: 20 μm.

Remarks

This species was first described from Zhejiang Province by Shi et al. (2009) and can be easily distinguished from other known species of the genus by two small blue spots on Th. III, five mac on Abd. III laterally, presence of A2 on Abd. IV. The characters of our specimens agree well with the original description in chaetotaxy of body, labium, colour pattern, and other characters, but there are five smooth chaetae on posterior face of ventral tube from Zhejiang and four smooth chaetae from that from Jiangxi. In fact, the number of smooth chaetae on posterior face of ventral tube may varies intraspecifically from two to five in some species of the genus. Chaetotaxy of manubrial plaque is added here.

Distribution

China (Jiangxi, Zhejiang).

Homidia socia Denis, 1929

Figs 76, 77, 78, 79, 80, 81–86

Homidia socia Denis, 1929: 310.

Examined specimens

3♀ on slides, China, Jiangxi Province, Nanchang City, Xinjian District, Jiuxi, 28°47'56"N, 115°45'11"E, 168 m asl, sample number 1243, collected by Y-T Ma, 12-XI-2020.

Description

Size. Body length up to 2.16 mm.

Colouration. Ground ground colour pale yellow. Ant. I–IV with scattered blue pigment. Eye patches dark blue. A pair of longitudinal blue stripes present along lateral side of head to Abd. III. Medial longitudinal narrow stripe present from Th. II to Abd. III. Abd. V with blue pigment (Fig. 76).

Figure 76. 

Habitus of Homidia socia Scale bar: 500 μm.

Head. Antenna 0.52–0.66× body length; antennal segment ratio I: II: III: IV = 1: 1.28–1.40: 1.00–1.20: 1.67–2.11. Eyes 8 + 8, G and H smaller than others, interocular chaetae with p, r, and t. Dorsal cephalic chaetotaxy with three antennal (A), three ocellar (O) and five sutural (S) mac (Fig. 77). Chaetal formula of labial base as MREL1L2, all ciliate, R/M as 0.67–0.72.

Figures 77, 78. 

Homidia socia 77 dorsal chaetotaxy of head 78 chaetotaxy of Th. II–III. Scale bars: 20 μm (77); 50 μm (78).

Thorax. Th. II with four medio-medial (m1, m2, m2i, m2i2), three medio-sublateral (m4, m4i, m4p), 30–33 (24) posterior mac. Th. III with 41–45 mac and two sens (Fig. 78). Pseudopores on coxa I–III as 2, 3, 2, respectively; coxal macrochaetal formula as 3/4+3, 3/4+2. Trochanteral organ with 39 smooth chaetae. Tenent hairs clavate and almost equal to inner edge of unguis. Unguis with four inner teeth, basal pair located at 0.38–0.45 distance from base of inner edge of unguis, distal unpaired teeth at 0.65–0.67 and 0.80–0.85 distance from base; unguiculus lanceolate, outer edge slightly serrate.

Abdomen. Range of Abd. IV length as 6.25–10.12× as dorsal axial length of Abd. III. Abd. I with 10 (a2, a3, a5, a5i, m2–5, m2i, m4i, m4p) mac, ms antero-external to sens. Abd. II with six (a2, a3, m3, m3e, m3ea, m3ep) central, one (m5) lateral mac, and two sens. Abd. III with two or three (a2, m3, a3 sometimes absent) central and four (am6, pm6, m7a, p6) lateral mac, one ms, and two sens (Fig. 79). Abd. IV anteriorly with eight or nine mac arranged in irregular transverse row, A2 always present and anterior to transverse row; posteriorly with 6–10 central mac; laterally with 18–22 mac (Fig. 80). Anterior face of ventral tube with 39 ciliate chaetae, 3+3 of them as mac, line connecting proximal (Pr) and external-distal (Ed) mac oblique to median furrow (Fig. 81); posterior face with two distal smooth and numerous ciliate chaetae; lateral flap with six smooth and 24 ciliate chaetae (Fig. 82). Manubrial plaque dorsally with 11–14 ciliate chaetae and three pseudopores (Fig. 83); ventrally with 26 ciliate chaetae on each side (Fig. 84). Dens with 15 smooth inner spines (Fig. 85). Mucro bidentate with subapical tooth larger than apical one; tip of basal spine reaching apex of subapical tooth; distal smooth section of dens shorter than mucro in length (Fig. 86).

Figure 79. 

Chaetotaxy of Abd. I–III of Homidia socia. Scale bar: 50 μm.

Figure 80. 

Chaetotaxy of Abd. IV of Homidia socia. Scale bar: 50 μm.

Figures 81–86. 

Homidia socia 81 anterior face of ventral tube 82 posterior face and lateral flap of ventral tube 83 manubrial plaque 84 ventro-apical part of manubrium 85 proximal section of dens (circles also representing spines) 86 mucro. Scale bars: 20 μm.

Ecology

In the litter of leaves of Phyllostachys edulis.

Remarks

This species was first described from Fujian Province, China by Denis (1929), mainly based on its colour pattern with three longitudinal stripes on dorsal side. Yosii (1942), Stach (1965), Lee and Park (1989), and Chiristiansen and Bellinger (1980, 1992) reported it from Japan, Vietnam, Taiwan (China), and USA, respectively, and their descriptions were relatively simple. Jordana (2012) also reported it based on Vietnamese and Japanese specimens that corresponded in colour pattern to H. socia forma flava Yosii, 1953 from Japan. In this work, several characters not previously mentioned are added, such as the chaetotaxy of the head, ventral tube, and manubrial plaque. Differences exist between the specimens collected from Jiangxi Province and other authors’ previous descriptions that are listed in Table 4. Our specimens, with 15 spines on dens, are similar to those examined by Jordana (2012) which had 14 spines. Up to 30 spines were given by Denis (1929) for the type specimens of large size from Fujian. These specimens or specimens from the type locality will therefore need to be redescribed to confirm the assignment of our specimens as well as those described by Jordana (2012) to H. socia.

Table 4.
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Comparison of H. socia between different descriptions.

Characters This work Denis (1929) Christiansen and Bellinger (1980, 1992) Stach (1965) Jordana (2012)
Chaetal formula of labial base MREL1L2 unknown MREL1L2 unknown unknown
Mac on Abd. I 10 unknown 11 or 15 9 unknown
Central mac on Abd. II 6 unknown 5–6 6 6
Central mac on Abd. III 2–3 unknown 3 3 3
Mac A2 on Abd. IV present unknown present unknown present
Mac of transverse row on Abd. IV 8–9 unknown 8 8 7
Centro-posterior mac on Abd. IV 6–10 unknown 5 8 5
Dental spines 15 up to 30 <20 7 or 11 14*

* Jordana (2012) gave 14 spines on dens on the specimens of Vietnam and Japan he examined, and 14–30 spines in the species redescription that included the values given by Denis (1929) in the original description.

Distribution

Japan, USA, Vietnam, and China (Anhui, Fujian, Guangxi, Jiangsu, Jiangxi, Taiwan, Zhejiang).

Discussion

The genus contains 75 known species that are distributed in the U.S.A. and the eastern part of Asia, especially China, Korea, and Japan (Table 5). They usually live in coastal areas from tropical to temperate zones, maybe because humidity is high in these regions. Most species of the genus are endemic (Table 5). However, some of them, such as H. sauteri and H. socia, are widespread, and were reported from China, Japan, Korea, and the U.S.A. Jia et al. (2005) pointed out that these two species are so widely distributed that they may have been transported by human activity. This hypothesis would, however, need more evidence.

Table 5.
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Distribution records of Homidia species around the world.

Species China Japan Korea India Indonesia & Singapore Vietnam USA
H. acutus sp. nov. √
H. allospila (Börner, 1909) √
H. amethystinoides Jordana & Baquero, 2010 √
H. anhuiensis Li & Chen, 1997 √
H. apigmenta Shi, Pan & Zhang, 2010 √
H. breviseta Pan, 2022 √
H. changensis sp. nov. √
H. chosonica Szeptycki, 1973 √
H. chroma Pan & Yang, 2019 √
H. chrysothrix Yosii, 1942 √
H. cingula (Börner, 1906) √
H. dianbaiensis (Lin, 1985) √
H. emeiensis Jia, Chen & Christiansen, 2004 √
H. fascia Wang & Chen, 2001 √
H. flava Yosii, 1953 √
H. flavonigra Szeptycki, 1973 √
H. formosana Uchida, 1943 √
H. fujiyamai Uchida, 1954 √
H. glassa Nguyen, 2001 √
H. grisea Lee & Lee, 1981 √
H. haikea Christiansen & Bellinger, 1992 √
H. hangzhouensis Pan & Ma, 2021 √
H. heugsanica Lee & Park, 1984 √
H. hexaseta Pan, Shi & Zhang, 2011 √
H. hihiu Christiansen & Bellinger, 1992 √
H. hjesanica Szeptycki, 1973 √
H. huashanensis Jia, Chen & Christiansen, 2005 √
H. insularis (Carpenter, 1904) √
H. jordanai Pan, Shi & Zhang, 2011 √
H. kali (Imms, 1912) √
H. koreana Lee & Lee, 1981 √
H. laha Christiansen & Bellinger, 1992 √ √
H. lakhanpurii Baquero & Jordana, 2015 √ √
H. latifolia Chen & Li, 1999 √
H. leei Chen & Li, 1997 √
H. leniseta Pan & Yang, 2019 √
H. linhaiensis Shi, Pan & Qi, 2009 √
H. maijiensis Zhou & Ma, 2022 √
H. mediaseta Lee & Lee, 1981 √
H. mediofascia Shi, Pan & Bai, 2009 √
H. minuta Kim & Lee, 1995 √
H. multidentata Nguyen, 2005 √
H. munda Yosii, 1956 √ √
H. nigra Lee & Lee, 1981 √
H. nigrifascia Ma & Pan, 2017 √
H. nigrocephala Uchida, 1943 √ √
H. obliquistria Ma & Pan, 2017 √
H. pentachaeta Li & Christiansen, 1997 √
H. phjongjangica Szeptycki, 1973 √ √
H. polyseta Chen, 1998 √
H. pseudofascia Pan, Zhang & Li, 2015 √
H. pseudoformosana Kang & Park, 2012 √
H. pseudosinensis Shi & Pan, 2012 √
H. qimenensis Yi & Chen, 1999 √
H. quadrimaculata Pan, 2015 √
H. quadriseta Pan, 2018 √
H. rosannae Jordana & Baquero, 2010 √
H. sauteri (Börner, 1909) √ √ √ √
H. sichuanensis Jia, Zhang & Jordana, 2010 √
H. similis Szeptycki, 1973 √ √
H. sinensis Denis, 1929 √ √ √
H. socia Denis, 1929 √ √ √ √
H. sotoi Jordana & Baquero, 2010 √
H. speciosa Szeptycki, 1973 √
H. subcingula Denis, 1948 √
H. taibaiensis Yuan & Pan, 2013 √
H. tiantaiensis Chen & Lin, 1998 √
H. tibetensis Chen & Zhong, 1998 √
H. transitoria Denis, 1929 √
H. triangulimacula Pan & Shi, 2015 √
H. unichaeta Pan, Shi & Zhang, 2010 √ √
H. wanensis Pan & Ma, 2021 √
H. xianjuensis Wu & Pan, 2016 √
H. yandangensis Pan, 2015 √
H. yosiii Jordana & Baquero, 2010 √
H. zhangi Pan & Shi, 2012 √
H. ziguiensis Jia, Chen & Christiansen, 2003 √

Most species of Homidia are heavily pigmented and their colour patterns vary only slightly among specimens of the same species, so colour pattern appears to be a significant character for the morphological taxonomy of the genus. However, colour pattern may exhibit some variability between some species, such as H. fascia Wang & Chen, 2001 and H. pseudofascia Pan, Zhang & Li, 2015. The new species, H. acutus sp. nov. described here shares almost the same colour pattern as H. zhangi, but the differences in other characters are significant.

Key to the Chinese species of Homidia

1 Mental chaetae expanded or leaf-like 2
– Mental chaetae normal ciliate 9
2 Body without obvious colour pattern except eye patches H. apigmenta
– Body with obvious colour pattern except eye patches 3
3 Abd. I–III laterally with oblique stripes H. obliquistria
– Abd. I–III laterally without oblique stripes 4
4 Abd. IV with mac A2 H. ziguiensis
– Abd. IV without mac A2 5
5 Central Abd. IV with roughly Y-shaped patch H. qimenensis
– Abd. IV without Y-shaped patch 6
6 Abd. IV anteriorly with an interrupted dark transverse stripe 7
– Abd. IV anteriorly without dark transverse stripe 8
7 Abd. IV anteriorly with 4–7 mac on each side H. latifolia
– Abd. IV anteriorly with 22–24 mac on each side H. polyseta
8 Labial basal chaetae L1 and L2 expanded H. triangulimacula
– Labial basal chaetae L1 and L2 unexpanded H. wanensis
9 Body without obvious colour pattern except eye patches 10
– Body with obvious colour pattern except eye patches 12
10 Labial basal chaeta L1 ciliate, Abd. III without mac a2 H. jordanai
– Labial basal chaeta L1 smooth, Abd. III with mac a2 11
11 Abd. IV anteriorly with 3–8 mac and posteriorly 1 mac on each side H. unichaeta
– Abd. IV anteriorly with 10–12 mac and posteriorly 2 mac on each side H. tibetensis
12 Head entirely dark 13
– Head not entirely dark 15
13 Abd. IV anteriorly with a transverse stripe H. nigrocephala
– Abd. IV anteriorly without transverse stripe 14
14 Th. II–III entirely dark H. anhuiensis
– Th. II–III with slightly brown pigment H. taibaiensis
15 Abd. IV with mac A2 .16
– Abd. IV without mac A2 18
16 Labial basal chaetae E & L1 ciliate H. socia
– Labial basal chaetae e & l1 smooth 17
17 Abd. III laterally with 5 mac H. linhaiensis
– Abd. III laterally with 4 mac H. tiantaiensis
18 Abd. IV almost entirely dark or with uniform colour 19
– Abd. IV with some colour patterns 25
19 Abd. IV almost entirely dark H. emeiensis
– Abd. IV not entirely dark 20
20 Abd. III laterally with 5 chaetae H. pentachaeta
– Abd. III laterally with 4 chaetae 21
21 Tenent hairs pointed H. acutus sp. nov.
– Tenent hairs clavate 22
22 Th. II–III medially with a longitudinal stripe H. yandangensis
– Th. II–III medially without a longitudinal stripe 23
23 Th. III without mac p4, labial chaeta L1 smooth H. zhangi
– Th. III with mac p4, labial chaeta L1 ciliate 24
24 Ground colour hazel, dens with 80–114 spines H. huashanensis
– Ground colour yellow, dens with 16–28 spines H. changensis sp. nov.
25 Abd. III without obvious colour pattern 26
– Abd. III with obvious colour pattern 34
26 Th. II medially with colour pattern 27
– Th. II medially without colour pattern 29
27 Th. II medially with a longitudinal stripe H. mediofascia
– Th. II medially with a pair of stripes 28
28 Th. III with a pair of patches .H. fascia
– Th. III without a pair of patches H. pseudofascia
29 Abd. IV anteriorly with obvious colour pattern 30
– Abd. IV anteriorly without obvious colour pattern 32
30 Mac a2 on Abd. III absent H. formosana
– Mac a2 on Abd. III present 31
31 Head with 8 sutural mac H. hangzhouensis
– Head with 9 sutural mac H. hexaseta
32 Ground colour pale yellow H. dianbaiensis
– Ground colour not pale yellow .33
33 Labial basal chaeta E ciliate H. maijiensis
– Labial basal chaeta e smooth H. phjongjangica
34 Abd. IV anteriorly with 2 mac on each side 35
– Abd. IV anteriorly with more than 2 mac on each side 36
35 Labial chaetae l1 and l2 smooth H. leniseta
– Labial chaetae l1 and l2 ciliate H. quadriseta
36 Abd. IV posteriorly with 9–11 mac on each side H. xianjuensis
– Abd. IV posteriorly with less than 9 mac on each side 37
37 Th. III dorsally without obvious colour pattern 38
– Th. III dorsally with obvious colour pattern 40
38 Th. II medially with colour pattern, Abd. II entirely dark H. nigrifascia
– Th. II medially without colour pattern, Abd. II not entirely dark 39
39 Unguis with 3 inner teeth H. chroma
– Unguis with 4 inner teeth . H. laha
40 Th. II medially without colour pattern 41
– Th. II medially with colour pattern 45
41 Transverse band of Th. III not reaching lateral edge of body 42
– Transverse band of Th. III reaching lateral edge of body 43
42 Abd. I with 14 mac H. breviseta
– Abd. I with 9 mac H. similis
43 Dens with 10 spines H. transitoria
– Dens with more than 20 spines 44
44 Abd. IV centrally with a transverse band H. sauteri
– Abd. IV centrally without a transverse band H. sinensis
45 Labial basal chaeta E ciliate H. leei
– Labial basal chaeta e smooth 46
46 Th. II posteriorly with a M-shaped transverse stripe H. pseudosinensis
– Th. II posteriorly without a M-shaped transverse stripe 47
47 Labial basal chaeta l1 smooth H. quadrimaculata
– Labial basal chaeta L1 ciliate H. sichuanensis

Acknowledgements

This research was funded by the National Natural Science Foundation of China, grant number 36101880 and Large Instruments Open Foundation of Nantong University.

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