Lithobius (Monotarsobius) monoforaminis sp. n., a new species of lithobiid centipede from central China (Chilopoda, Lithobiomorpha, Lithobiidae)

Abstract The present paper describes a new species Lithobius (Monotarsobius) monoforaminis sp. n. (Lithobiomorpha: Lithobiidae) recently discovered from Shaanxi and Shanxi provinces, Central China. Morphologically it resembles Lithobius (Monotarsobius) minimus Farzalieva, 2006 from Eastern Kazakhstan, but could be well distinguished from the latter having only one pore on the coxae of legs 12–15 and different plectrotaxy, and by lacking a wart on the male tibia 15. A key to the Chinese Lithobius (Monotarsobius) species is presented.


Methods
All specimens were hand-collected under leaf litter or stones. The material was examined with the aid of a Motic-C microscope, made in China. Colour description is based on specimens in 75% alcohol, and body length is measured from anterior margin of the cephalic plate to posterior end of postpedal tergite. Type specimens are deposited in the College of Life Sciences, Hebei University, Baoding, China. Terminology for external anatomy follows Bonato et al. (2010).
The following abbreviations are used in the text and tables: T, TT = tergite, tergites; S, SS = sternite, sternites; C = coxa, t = trochanter, P = prefemur, F = femur, Ti = tibia, a = anterior, m = median, p = posterior. Etymology. The specific name refers to the presence of a single pore on the coxae of legs 12-15.
Colour: basal antennal articles pale yellow-brown to chocolate, transition to yellow brownish from the twelfth article onwards, distalmost one yellow-brownish; tergites yellow-brown; cephalic plate, TT 1, 14 and 15 pale yellow-brown; pleural region pale grey with a yellowish hue, SS pale grey to grey with a purple hue; distal part of forcipules brown, basal and proximal parts of forcipules, forcipular coxosternite and SS 14 and 15 pale yellow-brown; all legs pale purple to grey, basal tarsus pale purple, distal tarsus yellow-brown.
Antennae: composed of 16-22 articles, commonly 20+20 articles; basal article long about equal to wide, the second markedly longer than wide, following articles gradually shortening, distal article much longer than wide, up to 2.0-2.5 times as long as wide; abundant setae on the antennal surface, less so on the basal articles, gradually increase in density towards the fourth article, then more or less constant in number.
Cephalic plate: smooth, convex, pigment concentrated as close netlike vein, long equal to wide; tiny setae emerging from pores and long setae scattered sparsely over the whole surface; frontal marginal ridge with shallow anterior median furrow; posterior margin of cephalic plate straight (Fig. 1).
Ocelli: six-seven oval to rounded on each side (Fig. 2) situated in two irregular rows; terminal two comparatively large, other ocelli about equal in size; ocelli domed, translucent, usually darkly pigmented.
Tömösváry's organ: comparatively small ( Fig. 2-To), nearly rounded; situated at anterolateral margin of cephalic plate, slightly smaller than the adjoining ocelli or equal in size.
Tergites: smooth, without wrinkles, backside slightly hunched; T 1 posterolaterally narrower than anterolaterally, generally trapeziform, narrower than T 3 and the cephalic plate, T3 slightly narrower than the cephalic plate; posterior margin of T 1 slightly convex or straight, posterior margin of T 3 straight, posterior margin of TT 5, 8, 10, 12 and 14 slightly concave, posterior margin ridge of TT 3, 5, 8, 10 and 12 continuous; all posterior angles generally rounded, without triangular projections; lateral margin ridge of all tergites continuous; tiny setae scattered very sparsely over the surface.
Sternites: narrower posteriorly, generally trapeziform, comparatively smooth, setae emerging from pores scattered very sparsely over the surface, 1-3 slightly long setae on the surface of the anterior part of each sternite, 1-2 slightly long setae on the surface of the posterior part of each sternite.
Legs: strong, tarsi fused on legs 1-13, well-defined on legs 14 and 15; all legs with claws, fairly long, curved ventrad; anterior and posterior accessory spines on legs 1-14, the anterior one moderately slender, forming a small angle with the claw, the posterior spine short and strong, forming a large angle with the claw; no accessory spines on legs 15. Short to comparatively long setae scattered very sparsely over the surface of all segments of all legs, more setae scattered on the surface of tarsus; legs 14 and 15 thicker and stronger than other legs in the male; tarsus 1 4.4-5.5 times as long as wide, tarsus 2 about 73.3%-95.7% length of tarsus on legs 15. Plectrotaxy as in Table 1.
Coxal pores: 1111, round; coxal pore field set in a relatively shallow groove, the fringe of coxal pore-field with slightly eminence.
Female S 15: generally trapeziform, anterior half being broader posterior margin straight, long setae scattered sparsely over the surface; the sternite of genital segment well chitinised, wider than long; posterior margin of genital sternite deeply concave between the condyles of gonopods, except for a small, median approximately fingerlike bulge; short to long setae sparsely scattered over the ventral surface of the genital segment. Female gonopod: first article fairly broad, bearing 6-8 long setae, arranged in 3 irregular rows; 2+2 moderately small, coniform spurs, inner spur smaller (Fig. 4); second article with 3-4 rather long setae arranged in 2 irregular rows on its ventral side and two stout dorsolateral setae; third article usually with 2-3 long setae on its ventral surface and one stout dorsolateral seta; terminal claw tridentate, outer and inner denticles smaller than the middle one (Fig. 5).
Male S 15: trapeziform, the anterior half being broader; posterior margin straight, long setae scattered sparsely over the surface. Male first genital sternite: wider than long, usually well chitinized; posterior margin quite deeply concave between the gonopods, no bulge medially; comparatively long setae evenly scattered on the ventral surface, few setae near the S 15; gonopods short and small, with 1-2 long setae, apically slightly chitinized (Fig. 6).
Habitat preferences. The specimens were collected under stones and in leaf litter in a Larix forest.

Key to the Chinese species of Lithobius (Monotarsobius)
To assist in the identification of the Chinese species of Lithobius (Monotarsobius), the following key is offered. This key emphasizes characters that can be examined without high-magnification microscopy; moreover, these characters are specific to the taxa occurring in China.  (Takakuwa, 1941)