Type material. Holotype: male, Cave of the brickyard of Gaofeng village, Yancang Town, Yi-Hui-Miao Autonomous County of Weining , Bijie City, Guizhou Province, 26°54'30.95"N, 104°24'13.78"E, alt. 2430 m a.s.l., 19 V 2017, Huiming Chen leg. Paratypes: 1 ♀, 1 ♂, same data as holotype. Other material. 4♂♂(larvae), the Gaodiping Cave of Dashan village, shaanqiao street, Yi-Hui-Miao Autonomous County of Weining , Bijie City, Guizhou Province, 26°50'55.03"N, 104°17'08.81"E, alt. 2175 m a.s.l., 23 IV 2017, Huiming Chen leg.

Antennae with 26 articles, no ocelli, anterior margin of the coxosternite with 5+5 teeth, more or less developed, porodonts slender, between fourth and fifth outer teeth. Tergites without posterior triangular projections, trachea connected to the valve of the T III clearly visible from the dorsal side. Coxal pores 4–6. Tarsal articulation well defined on legs I–XV. No secondary sexual modifications on legs XIV and XV of male. Female gonopods with simple claw, 2+2 spurs. Male gonopods short and small blunt cone bulge, apically slightly sclerotized.

Body length 17.43 –19.24 mm, cephalic plate 1.76–1.93 mm long, 1.77–1.97 mm wide; the whole body pale yellow–brownish, tarsus II of all legs more darker, proximal parts of forcipules and the teeth of the anterior margin of the coxosternite brown, all claws of legs yellow–brown.

Antennae with 26+26 articles; basal article slightly longer than wide, subsequent articles markedly longer than wide, distal article up to 2.5 times as long as wide. Abundant long setae on antennal surface, less so on basal articles, gradual increase in density of setae to about the fourth article, then more or less constant. Length of antenna 7.3–7.4 times width of cephalic plate, and often extending close to posterior edge of T XI (Figure 1).

Figures 1–12. 

Australobius tracheoperspicuus sp. n. (holotype male 1–5, 7–9, 11–12 paratype female 6 and 10) 1 Habitus, dorsal view 2 Tömösváry’s organ, lateral view 3 Cephalic plate, dorsal view 4 Cephalic plate, ventral view 5 Forcipular coxosternite, ventral view 6 T III of female 7 T III of male 8SS I–V 9SS VI and VII 10 Posterior segments and gonopods of female, ventral view 11 Posterior segments and gonopods in male, ventral view 12 Living specimen of Australobius tracheoperspicuus sp. n. 13 Cave of the brickyard of Gaofeng village.

No ocelli on each side of the cephalic plate. Tömösváry’s organ ovate, situated at anterolateral margin of the cephalic plate (Figure 2).

Cephalic plate smooth, convex, very slightly wider than long; tiny setae emerging from pores scattered very sparsely over whole surface; frontal marginal ridge with shallow anterior median furrow; from short to long setae scattered along marginal ridge of cephalic plate, there more setae close to the antenna; lateral marginal ridge discontinuous (Figure 3).

Forcipular coxosternite subtrapezoidal (Figure 4), anterior margin broad, external side lightly longer than internal side; median diastema moderately narrow, deeply V–shaped; anterior margin with 5+5 blunt teeth; porodonts slender, lying between the fourth and fifth outer teeth, and more closer to the fourth tooth, the innermost tooth more posterior, and the interdental distance gradually increases from the internal side to the external side (Figure 5); some short setae scattered on the ventral side of coxosternite; usually there are more setae near the dental margin.

All tergites with wrinkles, central backside slightly hunched, T I posterolaterally narrower than anterolaterally, generally trapeziform, narrower than cephalic plate, broader than T III. Trachea connected to the valve of the T III is clearly visible from the dorsal side (Figs 6–7). Posterior margin of T I slightly concave, posterior margin of TT III, V, VII, VIII, X, XII, XIV and XV concave. Marginal ridge of TT II , IV, VI, IX, X, XI, XII , XIII, XIV and XV bulging; lateral marginal ridge of all tergites continuous; all posterior angles generally rounded, without triangular projections; tiny setae scattered very sparsely over surface, more densely on anterior and posterior angles (Figure 1). All the tergites more longer than the congeneric species, T X is the longest, at most up to 1.3 times as long as wide.

Posterior side of sternites narrower than anterior one, generally trapeziform, comparatively smooth, long and thick setae emerging from pores scattered sparsely on surface, more setae on surface of the SS I–V (Figure 8), there are two irregular rows short and slightly thinker setae along the posterior margin of the SS VI and VII (Figure 9), few setae on surface of the following SS.

Legs long and slender, tarsal articulation well defined on legs I-IV; all legs with fairly long curved claws; anterior and posterior accessory spurs on legs I–XIII anterior accessory spurs moderately long and slender, forming an angle of about 45° with tarsal claws; posterior one slightly strong, forming an angle of about 30° with tarsal claws; no accessory spurs on legs XIV and XV. Comparatively long setae scattered very sparsely over surface of prefemur, femur, tibia and tarsus of legs I–XIII, more setae scattered on surface of tarsus; dorsal setae slightly longer than ventral, however, more setae in ventral; setae scattered on surface of legs XIV and XV clearly scarcer and short and fine than on other legs. Legs XIV and XV hardly thicker and stronger in both male and female, tarsus I about 6.3–6.6 times as long as wide in legs XV. Tarsus I of legs XV 5.0–5.6 times as long as wide in male, tarsus I of legs XV 5.0–5.6 times as long as wide in male. Leg plectrotaxy as in Table 1.

Coxal pores 4–6, most of them round, few ovate, 5-5-6-5 or 5-6-5-5 in female, 4-5-5-4 or 4-4-4-4 in male, coxal pore field set in a relatively shallow groove, fringe of coxal pore field with eminence, moderately long setae scattered sparsely over surface of eminence.

Female S XV anterolaterally broader than posterolaterally, generally trapeziform, posteromedially straight; sternite of genital segment usually well chitinised; posterior margin of genital sternite deeply concave between condyles of gonopods, except for a small, median bulge; long setae scattered over ventral surface of genital segment, regularly fringed, with longer setae along posterior margin. Gonopods: first article fairly broad, second moderately long and slender, coniform spurs in right, inner spur obviously larger than outer one (Figure 10); apical claw of third article simple, slender and sharp (Figure 11). Many long setae on surface of all segments of gonopods.

Male S XV posterolaterally narrower than anterolaterally, posterior edge straight, sparsely covered with long setae; sternite of genital segment smaller than in female, usually well sclerotised. Posterior margin quite deeply concave between gonopods, without a medial bulge; comparatively long setae scattered on ventral surface of genital segment, few slender setae near S XV, setae gradually increasing in density from anterior to posterior, gonopods short and small blunt cone bulge, apically slightly sclerotised (Figure 10).

The specific name refers to the trachea connected to the valve of the T III that is clearly visible from the dorsal side.

The specimens were collected on the limestone walls and bedrock floor of the cave.

The new species resembles A. magnus (Trozina>, 1894) from North-Western China in having the coxal pores numbering 6–7, no accessory spurs on legs XIV and XV, DaC spine present on legs XIII–XV, apical claw of female gonopods simple. However, the new species can be easily distinguished by the following characters: trachea connected to the valve of the TIII clearly visible from the dorsal side in new species instead of the trachea connected to the valve of the TIII is invisible from the dorsal side in A. magnus; absence of ocellus on each side of the cephalic plate vs. 8–9 ocelli in A. magnus; DaC spine being only present on the XIII^th–XV^th legs in contrast to being present or absent on VIII^th–X^th legs, present on X^th –XV^th legs in A. magnus.

On the other hand, several diagnostic features of the recently described Chinese species that are routinely used in the diagnosis of species of Australobius Chamberlin, 1920 are variable within the framework of the original description, perhaps the most conspicuous variation pertains to the number of teeth on the anterior margin of the coxosternite and the numbers of the antennal articles and the ocelli. For example, in the original description of the genus Australobius, the number of antennal articles is mostly 20, some species more than 24 articles, whereas in many species occurring in China it is higher (Table 2). The same is true for the number of the ocelli, which is few (e.g., 1+3–1+6) or in some species more than 8 in the original description of the genus, whereas in many species occurring in China it is higher (Table 2), and for the number of coxosternal teeth, which is at least 3+3 in the original description, whereas in many species occurring in China it is more variable (Table 2).

To assist in the identification of the Chinese species of Australobius, numbers of examined specimens, distribution and main morphological characters of the known species of this genus in China is presented (Table 2) and key to the known Chinese species of the genus is presented, these characters are specific only to adults of the taxa occurring in China.