A new species of Lithobius (Monotarsobius) Verhoeff, 1905 (Lithobiomorpha, Lithobiidae) from China

Abstract The present paper deals with a new species of the genus Lithobius Leach, 1814, Lithobius (Monotarsobius) songi sp. n.(Lithobiomorpha: Lithobiidae) recently discovered in Hebei Province, China. Morphologically it resembles Lithobius (Monotarsobius) holstii (Pocock, 1895) from China and Japan but could be well distinguished from latter by havinga Tömösváry’s organ slightly smaller than the adjoining ocelli, different leg plectrotaxy and tridentate claw of female gonopods. A key to the Chinese Lithobius (Monotarsobius)species is presented.


Methods
All specimens were hand-collected under stones. Th e material was examined with the aid of a Motic-C microscope, made in China. Colour description is based on specimens in 75% ethanol, and body length is measured from anterior margin of the cephalic plate to posterior end of telson. Type specimens are preserved in 75% ethanol and deposited in the College of Life Sciences, Hebei University, Baoding, China; some nontype material is deposited in the Department of Life Sciences, Hengshgui University, Hengshui, China. Terminology for external anatomy follows Bonato et al. (2010).
Description: Body 5.9-6.9 mm long; cephalic plate 0.6-0.7 mm long, 0.6-0.7 mm wide. Colour: tergites and basal articles pale brown; transition to yellow brownish from the seventh or eighth articles onwards, the terminal article yellow brown; tergites pale chestnut; pleural region pale gray; SS pale orange; distal part of forcipules brown, the remaining part of forcipules, forcipular coxosternite and SS 14 and 15 pale yellowbrownish; all legs pale yellow-brownish, tarsi of all legs yellow-brown.
Antennae composed of 19+19-21+21 articles ( Fig. 1), most often 19+19; basal article almost as long as wide, second one markedly longer than wide, succeeding articles gradually shortening; terminal article typically longer than wide, up to 2.3-2.9 times longer than wide. Antennal setation: abundant setae on antennal surface, but fewer setae on outer side and ventral and dorsal side in basal articles, gradual increase in density of setae to about fourth or fi fth article, then more or less constant.
Cephalic plate smooth, convex, as long as broad, covered with sparse tiny setae; anterior part of the cephalic capsule with shallow median sulcus; pigment concentrated as close netlike veins, few short to long setae scattered along the marginal ridge; lateral marginal ridge continuous; posterior margin straight, without widening in middle part (Fig. 1).
Six-seven ocelli on each side of cephalic plate (Fig. 2), more often 6, arranged in 2 irregular rows; the terminal one larger, the ocelli near the dorsal slightly larger, the ocelli near the ventral slightly smaller; overhanging the lateral margin of the cephalic plate; ocelli gently bulging, translucent, usually darkly pigmented.
Tömösváry's organ moderately small ( Fig. 2-To), nearly rounded, situated ventrad to anterolateral margin of cephalic pleurite, slightly smaller than the adjoining ocelli. Coxosternite (Fig. 3) approximately trapezoidal, anterior margin moderately narrow with 2+2 comparatively sharp coxosternal teeth, median diastema relatively deep, V-shaped (Fig. 3); coxosternal shoulder lacking; porodonts lying posterolateral to the lateral tooth, comparely long and slender, without a bulge at the base. Moderately short to long setae sparsely scattered over the dental margin, comparatively long and thick near the dental margin.
Legs strong, tarsus 1-2 articulation fused on legs 1-13, well-defi ned on legs 14 and 15; claw moderately long and curved ventrad in all legs; accessory spur on both anterior and posterior side of claw of legs 1-14, anterior accessory spur moderately long and thicker, forming a moderately large angle with the claw; posterior accessory spur short and slender, forming a comparatively small angle with the claw; no accessory claws on leg 15; short to moderately long setae scattered over the surface of legs 1-13, tarsi generally more setose, few setae on legs 14-15; legs 14 and 15 markedly thickened, the male more thicken than the female, tarsus 1 about 4.0-5.3 times longer than wide, tarsus 2 about 67%-81% length of tarsus on legs 15. Legs' plectrotaxy: as in Table 1.
Coxal pores arranged in a row, ovate to round, moderately small, 1222. Pore-fi eld set in a slightly shallow groove, 8 short to moderately long setae scattered sparsely over the margin of shallow groove.
Female S 15 posterolaterally narrower than anterolaterally, generally trapeziform, straight posteromedially; short to long setae scattered very sparsely over its surface and lateral margins. Th e sternite of genital segment usually well sclerotised, wider than long, posterior border moderately deeply concave between condyles of gonopods, except for a small, median approximately rhombic bulge, distally lightly sclerotised; short to moderately long setae evenly scattered over the surface of genital sternite except for middle and anterior parts. Female gonopods: basal article moderately broad, bearing 8 moderately long setae, arranged in 3 irregular rows, and 2+2 small coniform spurs; inner spur slightly smaller and more anterior than the outer (Fig. 4); second article with 6 moderately long setae, arranged in 2 irregular rows; usually 3-4 moderately long setae on the surface of third article; terminal claw tridentate (Fig. 5), dorsal and ventral tooth about same in size.
Male S 15 posterolaterally narrower than anterolaterally, generally trapeziform, straight posteromedially; short to long setae scattered very sparsely over its surface and lateral margins. Th e sternite of genital segment usually well sclerotised, wider than long; comparatively long setae about evenly scattered on the ventral surface, slightly fewer near S15. Posterior margin of the sternite of the genital segment quite deeply concave between gonopods, no bulge medially; gonopods short and small, only a small hemispherical bulge, with 1-2 long setae on surface, terminal slightly sclerotised (Fig. 6).
Distribution: Known only from the Hebei Province (Hengshui and Zhangjiakou Cities), NE China.
Remarks: Having an eye composed of 6-7 ocelli and about 20 antennal articles, the new species resembles L. (M.) holstii (Pocock, 1895) from China and Japan (Takakuwa Habitat preferences: Th e type series has been collected in a roadside of a mountain pine tree forest and under Chinese jujube trees in champaign environments.

Key to the Chinese species of Lithobius (Monotarsobius)
To assist in the identifi cation of the Chinese species of L. (Monotarsobius), the following key is off ered. Th is key emphasizes characters that can be examined without much dissection or high-magnifi cation microscopy; moreover, these characters are specifi c to the taxa occurring in China.  (Takakuwa, 1941)