Lithobius (Ezembius) varioporus, a new species from eastern China (Lithobiomorpha, Lithobiidae)

Abstract Lithobius (Ezembius) varioporussp. nov. (Lithobiomorpha, Lithobiidae), recently discovered from Longquanguan Town, Fuping County, Baoding City, Hebei Province, China, is described. Morphologically it resembles to Lithobius (Ezembius) laevidentata Pei, Ma, Hou, Zhu & Gai, 2015 from the Xinjiang Autonomous Region, but can be easily distinguished from the latter by the Tömösváry’s organ, slightly smaller than the adjoining ocelli, no secondary sexual modifications on male tibia 14 and 15, posterior accessory spine of legs 14 and 15 present and the number of coxal pores varying considerably from three to eight. The main morphological characters of the known Chinese species of the subgenusEzembius Chamberlin, 1919 based on adult specimens are presented.


Introduction
Ezembius was originally proposed as a subgenus of Lithobius Leach, 1814 in the family Lithobiidae by Chamberlin (1919); it accommodates a group of approximately 60 species and subspecies mostly known from Asia, with little extension into northwestern North America. Known species colonise a wide range of habitats, from the Arctic and sub-Arctic regions to tropical and sub-tropical forests, from steppe and overgrazed stony areas of central Asia to Himalayan montane forests, from the seashore up to 5500 m (Himalayas) (Zapparoli andEdgecombe 2011, Qiao et al. 2018). Although the subgenus was formally proposed as new (Chamberlin 1923), according to Jeekel (2005) its name was validated in 1919 (Chamberlin 1919). Ezembius is characterised by antennae with ca. 20 articles; ocelli 1+4-1+20; forcipular coxosternal teeth usually 2+2; porodonts generally setiform, sometimes stout. Tergites are generally without posterior triangular projections. Female gonopods are with uni-, bi-, or tridentate claws, and 2+2-3+3 (rarely 4+4) spurs (Zapparoli and Edgecombe 2011).
The myriapod fauna of China is still poorly known and very little attention has been paid to the study of Lithobiomorpha, with only 88 species and subspecies known from the country. Altogether, 25 species of Ezembius have been recorded from China, but only one of them has been reported from Hebei Province , Qiao et al. 2019a. Herein, a new species recently discovered in the Hebei Province, China, is described and illustrated. Tables of the main morphological characters of Chinese Ezembius species are also presented.

Materials and methods
All specimens were hand-collected under leaf litter or stones. The material was examined with the aid of a Nikon SMZ-1500 stereo microscope equipped with a drawing attachment. The colour description is based on specimens preserved in 75 % ethanol, and the body length is measured from the anterior margin of the cephalic plate to the posterior margin of the postpedal tergite. Type specimens are preserved in 75 % ethanol and deposited in the School of Life Sciences, Hengshui University, Hengshui, China (HUSLS). The terminology of the external anatomy follows Bonato et al. (2010).
The following abbreviations are used in the text and the tables: Cephalic plate smooth, convex, slightly longer than wide; tiny setae emerging from setal sockets scattered very sparsely over the whole surface; frontal marginal ridge with shallow anterior median furrow; short to long setae scattered along the marginal ridge of the cephalic plate; lateral marginal ridge discontinuous, posterior margin continuous, straight, wider than lateral marginal ridge, the middle of the posterior edge is very slightly concaved forward (Fig. 1). Nine to ten approximate oval ocelli on each side (Figs 2, 3), domed, translucent, usually darkly pigmented, situated in three irregular rows; the pos terior two ocelli comparatively large; others subequal in size. Tömösváry's organ situated at anterolateral margin of the cephalic plate, slightly smaller than the adjoining ocelli and lying well apart from them (Figs 2, 3).
All tergites smooth, without wrinkles, dorsum slightly convex; tiny setae emerging from setal sockets scattered sparsely over the entire surface, few long setae near the margin. Lateral marginal ridges of all tergites continuous. Posterior margin of TT 1, 3, and 5 feebly concave, posterior marginal ridges continuous, posterior margins of TT 7, 8, 10, 12, and 14 feebly concave, posterior marginal ridges discon tinuous. Posterior angles of tergites generally rounded, without triangular projections. Miniscule setae scattered sparsely over the surface, two or three slightly thick and long setae on anterior and posterior angles of each tergite.
Sternites. Posterior side narrower than anterior side, generally inverted trapezoidal, smooth; setae emerging from setal sockets sparsely scattered on the surface and lateral margin, 3-5 long setae on the surface of the anterior part of each sternite, two or three comparatively long setae scattered sparsely on the surface of the pos terior part of each sternite.
Legs robust, tarsal articulation ill-defined on legs 1-13, faint trace on ventral side, well-defined on legs 14 and 15; short to long setae sparsely scattered over the surface of prefemur, femur, tibia, and tarsus of all legs, with more setae on the tarsal surface; setae on dorsal and ventral surface of tarsus slightly longer than the anterior and posterior, one row of thicker setae regularly arranged on the medial ventral side of tibia of legs 1-13, with setae significantly reduced in legs 14 and 15, no thicker setae regularly arranged in one row on the medial ventral side of tibia. All legs with fairly long curved claws; legs 1-13 with anterior and posterior accessory spines; anterior accessory spines moderately long and slender, forming a moderately small angle with the claw, posterior accessory spines slightly more robust, forming a comparatively large angle with the claw, legs 14 and 15 only with small posterior accessory spines; legs 14 and 15 moderately thicker and longer than the anterior pairs in the female; In the female, tarsus 1 4.0-6.0 times as long as wide in legs 15, tarsus 2 ca. 73.1 %-77.3 % length of tarsus on legs 15; In the male, tarsus 1 3.3-7.3 times as long as wide in legs 15, tarsus 2 ca. 51.1 %-77.6 % length of tarsus on legs 15. Leg plectrotaxy provided in Table 1.
Female S 15 anterior margin broader than posterior, generally inverted trapezoidal, posteriomedially straight, colour usually yellow-brown; short to long sparse setae evenly scattered on surface; surface of the lateral sternal margin of genital segment well chitinised, posterior margin of genital sternite deeply concave between condyles of gonopods, except for a small, median approximately rhombic-shaped bulge; relatively long setae sparsely scattered over ventral surface of the genital segment. Gonopods (Figs 5, 6): first article fairly broad, bearing 22-26 moderately long setae, arranged in five irregular rows; generally with 3+3 (3+2 in only two specimens) moderately long and slender, coniform spurs, inner spur slightly smaller than the outer, dorsolateral setae absent; second article with 12-16 long setae, arranged in three irregular rows, 9-12 stout setae on the dorsal side; third article with five or six comparatively long setae, arranged in two irregular rows, four or five stout setae on the dorsal side; third article with a simple broad apical claw (Figs 5, 6).
Male S 15 posterior margin narrower than anterior, posteriomedially straight, sparsely covered with long setae on the surface; sternite of genital segment smaller than in female, usually well sclerotised, posterior margin deeply concave between the gonopods, without median bulge; long setae sparsely scattered on the ventral surface of the genital segment, fringed with longer setae along the poste rior margin; gonopods short, appearing as a small hemispherical bulge, with three or four long setae, apically slightly sclerotised (Fig. 7).
Habitat. The specimens studied here were collected from a mixed coniferous broad-leaved forest at ca. 500-1800 m above sea level, in moderately moist habitats under roadside stones and litter of the forest floor.
Etymology. The specific epithet varioporus refers to the coxal pore numbers varying considerably from three to eight. The new species must be also easily distinguished from the other Lithobius (Ezembius) species to date known from China by the coxal pore number, varying considerably from three to eight, not only among specimens, but also in the same individual.
To assist in the identification of the Lithobius species of the subgenus Ezembius from China, the main morphological characters based on adult specimens are presented in Table 3.