Diochus japonicus Cameron, 1930

Shuai, Qi, Nozaki, Tsubasa & Tang, Liang, 2021, Notes on the genus Diochus Erichson, with descriptions of two new species from China (Coleoptera, Staphylinidae), Zootaxa 4908 (2), pp. 276-282 : 278-279

1. Diochus japonicus Cameron, 1930

( Figs 1 , 4–15 )

Diochus japonicus Cameron, 1930: 206 .

Diochus bicornutus Zhou & Zhou, 2016: 6 ; syn. nov.

Material examined. Japan: Kumamoto Pref.: 1♁ 1♀, Hitoyoshi-shi, 15. X. 1977, Ôishi leg. ( KUM) ; China: Zhejiang: 1♀, Lin’an City, West Tianmushan , 15–16.VII.2000, Li-Zhen Li leg. ( SHNU); 3♁♁ 2♀, Longwangshan, 300– 500m, 24–26.IV.2004, Hu, Li, Tang & Zhu leg. ( SHNU); 2♁♁ 1♀, Baishanzu Conv., 1050–1700m, 5–7. V .2004, Hu, Tang & Zhu leg. ( SHNU) ; 2♀♀, Gutianshan, 5–7. V .2005, Li & Zhu leg. ( SHNU); 2♁♁ 1♀, Qingliangfeng, 1050– 1080m, 9–10. V .2005, Li & Zhu leg. ( SHNU); 1♁, Longwangshan , Anji County , 350–550m, 24.IV.2006, Shan-Jia Shen leg. ( SHNU); 3♁♁ 1♀, Xianju County, Danzhu, 150–600m, 31.V–2. VI .2006, Li & Shen leg. ( SHNU); 1♀, Lin’an City, West Tianmushan , 300–400m, 11–15. VI .2006, Hu & Tang leg. ( SHNU); 1♁ 3♀♀, Suichang County, Jiulongshan N. R ., 500–800m, 29–30.VII.2006, Li & Shen leg. ( SHNU); 3♁♁, Lin’an City, East Tianmushan , 650m, 25.IV.2008, He & Tang leg. ( SHNU) ; 1♀, Lin’an City, Longwangshan, 600–1000m, 19.VII.2009, Feng, Yin & Yuan leg. ( SHNU); 3♁♁ 4♀♀, Lin’an City, West Tianmushan , 300–400m, 29. V .2010, Wang, Xu & Zhu leg. ( SHNU) ; 1♀, Lin’an City, Tianmushan, Haoling, 830–900m, 31. V .2010, Wang, Xu & Zhu leg. ( SHNU); 1♁, Lin’an City, East Tianmushan , 1050–1150m, 13.IV.2011, Peng & Zhu leg. ( SHNU) ; 1♀, Lin’an City, West Tianmushan , 300– 1000m, 27.VII.2011, Yu-Hong Pan leg. ( SHNU) ; 1♀, Anji City, Qianmutian, 700–1325m, 28.VII.2011, Yu-Hong Pan leg. ( SHNU); 8♁♁ 13♀♀, Ningbo City, Yinjiang Town , Xishan, 200m, 18–22.VIII.2011, Jian-Qing Zhu leg. ( SHNU); 1 ♁ 3♀♀, Kaihua County, Gutianshan , 29°14’N, 118°08’E, 400–500m, 19. VI .2013, Li, Lv, Xie & Zheng leg. ( SHNU); 6♁♁, Longquan, Fengyangshan, Datianping , 27°54’36’’N, 119°10’20’’E, 1320m, bush leaf, moss, ferns, sifted, beating, 27.IV.2014, Peng, Song, Yan, Yin & Yu leg. ( SHNU); 4♁♁ 3♀♀, Qingyuan, Baishanzu N. R ., path nr. hotel, 27°44’42’’N, 119°10’19’’E, 1060–1130m, leaf litter, sifted, 30.IV.2014, Peng, Song, Yan, Yin & Yu leg. ( SHNU); 5♁♁ 1♀, Lin’an City, West Tianmushan, Mountain Grand Canyon , 30°22’54.68’’N, 119°27’49.71’’E, 749m, sifted, 6. V .2018, Cheng & Shen leg. ( SHNU); 2♁♁ 3♀♀, Quzhou City, Kaihua County, Gutianshan N. R ., 28°19’39.60’’N, 118°40’36.93’’E, 461m, mixed leaf litter, sifted, 14.VIII.2018, Cheng & Miao leg. ( SHNU) ; Fujian: 5♀♀, Wuyishan, 27–31. V .2002, Li-Zhen Li leg. ( SHNU); 1♁ 2♀♀, Wuyishan City, Guadun Vill. , 27°44’N, 117°38’E, 1100–1300m, 30. V .2012, Dai & Peng leg. ( SHNU); Anhui: 1♀, Guniujiang, 300m, 27.IV.2005, Hu & Tang leg. ( SHNU); 2♁♁, Huangshan, Tangkou Town, Hougu , 30°5’3.48’’N, 118°8’45.96’’E, 569–688m, 29.VI– 7.VII.2020, sifted, Tang, Li & Zhou leg. ( SHNU) .

Measurements. BL: 4.3–5.9 mm, FL: 2.4–2.8 mm. HL: 0.70–0.80 mm, HW: 0.54–0.62 mm, EyL: 0.18–0.23 mm, TL: 0.40–0.46 mm, PL: 0.91–1.05 mm, PW: 0.72–0.85 mm, EL: 0.91–1.02 mm, EW: 0.92–1.09 mm, SL: 0.63–0.72 mm. Head 1.22–1.41 times as long as wide, eye 0.40–0.55 times as long as tempora, pronotum 1.20–1.32 times as long as wide, elytra 0.90–1.07 times as long as wide.

Distribution. China (Fujian, Hainan?, Zhejiang, Guangxi, Yunnan, Anhui, Jilin?, Liaoning?), Japan. New to Anhui.

Remarks. Diochus bicornutus was described by Zhou & Zhou (2016) in a review of the Diochus species of China. The species is the most widely distributed Diochus species in China and was reported from Hainan, Fujian, Zhejiang, Guangxi and Yunnan. Diochus bicornutus can be recognized by the distinct secondary sexual characters of the male: head with an elongate elevation between eyes and sternite VIII with coarse setae along the posterior margin. However, these two characters are also shared with D. japonicus and D. conicollis . Before discussing the relationships of these three species mentioned above, a few characters of D. bicornutus mentioned in the original description must be fixed here:

1. “Right mandible with a smaller and not very sharp tooth ( Fig. 4J in Zhou & Zhou 2016)”. This character, one small inner tooth of right mandible, is unusual within Diochus . It seems that unfortunately, the right mandible illustrated in Zhou & Zhou, 2016 is damaged. We checked many specimens of D. bicornutus in our collections and in all specimens the right mandible ( Fig. 7 ) was bearing two inner teeth: a small one and a large one.

2. The body length, stated as “BL= (5.1–5.2) mm”, seems to be measured on a limited number of specimens. According to the measurements of specimens listed in this paper, the range of the body length should be expanded to 4.3–5.9 mm.

3. The shape of the head in the original description, stated as “HL to HW ratio 1.41”, is incorrectly measured or calculated. The measurements of head in the original description were given as “HL= (0.6–0.7) mm, HW= (0.5– 0.6) mm”, and therefore it is impossible arrive at such a ratio. The ratio be 1.22–1.41.

4. The configuration of the gular sutures was given as “Gular sutures deep, confluent at basal 1/4, then extended to base” in the original description of D. bicornutus , versus “Gular sutures deep, confluent at near base” in the redescription of D. conicollis . However, the gular sutures are not always stable in D. bicornutus . Forty-eight male specimens of D. bicornutus listed here were checked: 42 males with gular sutures confluent at basal 1/4, 6 males with gular sutures confluent at base or at a point closer to base than basal 1/4.

Therefore, the external differences among D. bicornutus , D. japonicus and D. conicollis mentioned in Zhou & Zhou’s paper no longer exist. Additionally, the female holotype of D. japonicus is the only specimen examined by Zhou & Zhou (2016). By comparing the aedeagi and spermathecae of D. japonicus and D. bicornutus in the present study, no striking differences were found and so Diochus bicornutus Zhou & Zhou, 2016 syn. nov. is here synonymized with D. japonicus Cameron, 1930 . The status of D. japonicus Cameron, 1930 is also doubtful, since D. japonicus shares nearly all characters with D. conicollis ( Motschulsky, 1858) . A male lectotype of D. conicollis was studied by Zhou & Zhou (2016) but the internal structures of the aedeagus were impossible for us interpret as illustrated. Thus, it will be necessary to get more specimens from or near the type locality of D. conicollis to clarify the status of D. conicollis and D. japonicus . Because of the variability observed in the structure of the mandibles and male sternite VIII for D. japonicus , D. conicollis , at present can be only reliably distinguished from D. japonicus by the reported smaller length of forebody (2.0– 2.2 mm), given by Zhou & Zhou (2016).

Due to some slight differences in the aedeagus between specimens of D. japonicus from Hainan and those from other populations, we only tentatively treat Hainan as part of this species’ distribution.

Figures

FIGURES 1–3. Habitus. 1—Diochus japonicus; 2—D. guizhouensis; 3—D. caudapiscis. Scale bars: 1 mm.

FIGURES 4–15. Sexual characters. 4–10—Diochus japonicus (Zhejiang); 11–15—D. japonicus (Japan); 4, 5, 6—aedeagus in ventral view; 7—mandibles; 8, 14—male sternite IX; 9, 13—male sternite VIII; 10, 15—spermatheca; 11—male head in dorsal view; 12—aedeagus in dorsal view. Scale bars: 0.25 mm.