Digitipes jonesii

Description. Length to 55 mm. 17 antennal articles (apart from two individuals with 18 / 18 and 18 / 19 articles); basal three articles glabrous dorsally (Figs 24, 30), ca 2.5 articles glabrous ventrally. Cephalic plate and tergites punctate. Longitudinal median furrow 10 – 20 % length of cephalic plate. Cephalic plate blue-olive green or blue anteriorly and mostly brown posteriorly; most of trunk tergites mixed blue-brown, darker in posterior half of trunk; basal (glabrous) part of antenna light blue, distal part variably purplish. Forcipular coxosternal tooth plate at least slightly wider than long, with four main teeth (Figs 25, 31), the inner two usually separated from the outer two (Figs 26, 32), sometimes partially fused, outer tooth smaller than the inner three; bases of tooth plates defined by oblique sutures diverging at a relatively obtuse angle of 135 – 150 °. Trochanteroprefemoral process with two distinct teeth along inner margin (Fig. 26). Second maxillary claw with slender accessory spurs. Article 2 of telopodite bearing a slender spine distally. Tergites with paramedian sutures complete from TT 6 to 8. Tergites marginate starting from 7 to 13, most specimens starting from 8 – 10. Tergites smooth apart from faint rugosity on lateral parts in some specimens; longitudinal median ridge mostly absent, a few specimens with a faint, posteriorly incomplete flat-topped ridge from TT 3 or 4. Sternites with paramedian sutures mostly 10 – 15 % length of sternites in mid body region, exceptionally confined to anterior edge of sternite. First three or four pairs of legs with two tarsal spurs, the subsequent up to 20 with one. A tibial and a femoral spur on leg 1 only. All articles of legs in some populations (especially in PS 3 of Joshi and Karanth 2012) bear numerous short, fine setae. Tergite of ultimate leg-bearing segment with gently convex lateral margins that faintly converge posteriorly; straight to weakly sinuous posterolateral margins, pointed posteromedially (Figs 28, 34). Sternite of ultimate legbearing segment with sides converging relatively strongly posteriorly, nearly straight, posterior margin moderately concave (Figs 29, 35). Coxopleural process mostly relatively short (Fig. 29), at most moderately long but stoutly conical in ventral view (Fig. 35), its long axis often oriented slightly laterally; two apical spines; lateral spine (s) either absent on both sides of coxopleural process (most common in PS 3 of Joshi and Karanth 2012), present only on one side, or present on both sides (most common in PS 2 of Joshi and Karanth 2012), ranging from minute to similar size to apical spines (Fig. 35). Pores relatively dense; pore field not reaching dorsal margin of coxopleuron (Figs 27, 33); nonporose area on coxopleural process narrow, from less than half length to posterior margin of sternite of ultimate leg-bearing segment to nearly reaching that margin. Ultimate leg prefemur with width at distal end ca 25 % its length; prefemoral spines mostly moderately large (Fig. 36): VL 2 or more commonly 3, VM 1 or usually 2, rarely 0, DM 0 or more commonly 1. Distomedial process in males bluntly conical (Fig. 43), extending distinctly further than distal end of the femur on its dorsal side, with a few fine setae on its apex (Fig. 37); shallow groove along distal 40 – 65 % of femur on its medial surface (Figs 38, 42). Ultimate leg tarsus 1 1.8 – 2.5 times length of tarsus 2; tarsus 1 3.3 – 4 times longer than pretarsus; pretarsus with pair of accessory claws.

Digitipes putative species 2. Joshi and Karanth, 2012: figs 2, 3, 6. Digitipes putative species 3. Joshi and Karanth, 2012: figs 2, 3, 6.

Diagnosis. Digitipes with basal three antennal articles glabrous dorsally. Tergite paramedian sutures complete from TT 6 to 8; tergites smooth, longitudinal median ridge usually absent, when present faint, incomplete. Coxopleural process relatively short, lateral spine variably present. Dorsomedial process on ultimate leg femur of male extending further than distal end of the femur on its dorsal side. Legs variably bearing many short, fine setae. Leg 20 with a tarsal spur.

Discussion. Lewis (2010 b) noted that the description of Arthrorhabdus jonesii Verhoeff, 1938, described from the Ponmudi Hills, corresponds closely to that of Otostigmus ceylonicus Hasse, 1887, and that this species could be a misplaced Otostigmus. Jangi and Dass (1984) did not identify any new material of this species, their description being extracted from Verhoeff (1938), and faunal lists by Sureshan et al. (2003, 2006) likewise attributed no new specimens to the species. Collecting at the type locality by JJ found only a single species that corresponds to the description of A. jonesii, Digitipes PS 2 of Joshi and Karanth (2012). Shared details include 17 antennal articles, three of which are glabrous, four teeth on each forcipular tooth plate, legs 1 – 4 with two tarsal spurs, a coxopleural process with two apical spines and a lateral spine, and three ventrolateral spines on the ultimate leg prefemur. Lewis (2010 b) noted that the original assignment of the species to Arthrorhabdus would predict that it has scolopendrine-type spiracles (i. e., with a three-flapped valve), but the holotype in fact has otostigmine-type spiracles, identical to those of Digitipes indicus (i. e., strongly elliptical on segment 3, rounded on the subsequent segments, with a humped atrium). The holotype of D. jonesii (Zoologische Staatssammlung, Munich) has the conformation of forcipular teeth (inner two teeth grouped, the outer tooth the smallest) and trochanteroprefemural process (two teeth on the inner margin) shared with Indian Digitipes. The specimen corresponds precisely to a female of Digitipes PS 2 of Joshi and Karanth (2012), which we cannot separate from D. indicus Jangi and Dass, 1984. Accordingly we place D. indicus in subjective synonymy of D. jonesii, and the putative record of Arthrorhabdus in India is removed. Digitipes jonesii groups putative species 2 and 3 of Joshi and Karanth (2012) because they cannot be distinguished by consistent morphological differences. In the mtDNA phylogeny, these two taxa were resolved as sister species. Both putative species are distinguished from several other Western Ghats Digitipes by having the basal three antennal articles being glabrous (shared with D. coonoorensis), including individuals with relatively setose legs, and having a long ultimate leg femoral process in the male. Specimens of putative species 2 differ from those of putative species 3 in the frequency of a lateral spine on the coxopleural process, a spine on both sides being the most common state in PS 2 (Figs 33, 35) and shared by the holotype of D. jonesii, but rare in PS 3 (Figs 27, 29). Both putative species include specimens with a spine on one side only, and while complete absence of lateral spines is the most frequent state in PS 3 (as in the holotype of D. indicus), PS 2 also includes several large specimens that lack lateral spines. As such, diagnostic value cannot be ascribed to this character, which appears to vary at the population level. Specimens of PS 2 have a more consistent formula of the ultimate leg prefemoral spines (VL 3, VM 2, DM 1), but within the variability exhibited by putative species 3 are individuals that correspond exactly to the (more stable) state of putative species 2. The relatively pronounced setae on the legs are unique to this clade when compared to other Indian Digitipes. Within PS 2, one of the two main clades identified by molecular phylogenetics (Joshi and Karanth 2012) has setae on the legs comparable to those more consistently shown by PS 3, whereas the other clade within PS 2 has less setose legs. The two clades within PS 2 occur in different mountain ranges, geographically close to each other. This feature thus displays some geographic variation between populations of what appears to represent a single species, and prohibits making a clear-cut distinction between PS 2 and PS 3 on the basis of leg setation. The two putative species are sympatric in their distributions in some parts of their ranges, largely in the southernmost hill ranges of the Western Ghats.

Material examined. 20 specimens of Digitipes putative species 3 (D. indicus of Joshi and Karanth, 2012) and 25 of Digitipes putative species 2 including CES 07196 and CES 07198 from the type locality of D. jonesii; CES registration numbers in Joshi and Karanth (2012: fig. 2, Table S 1). The specimens were collected from low and mid elevation forests (100 – 1500 msl) of the southern Western Ghats, including four specimens from the type locality of D. indicus (distribution maps in Joshi and Karanth 2012: fig. 5 c); all leg. J. Joshi, 2007 – 2010.