A strikingly coloured new giant millipede from Vietnam has copycat in Borneo (Diplopoda, Spirostreptida, Harpagophoridae)

A new giant species of the subfamily Rhynchoproctinae with strikingly bi-coloured, redyellow legs contrasting with a black body is described: Alienostreptus bicoloripes sp. nov. from Vietnam. The new species is assigned to the genus Alienostreptus Pimvichai, Enghoff & Panha, 2010 hitherto comprising one species, A. alienus (Attems, 1936), and diff ering from other rhynchoproctine genera by having the femoral spine duplicated. Species of this genus share three synapomorphic characters of the subfamily, viz (1) anterior coxal fold forms deep concavity in posterior view, (2) posterior coxal fold very low, and (3) posterior coxal fold with mesal fl ap. A superfi cially very similar colourful species from Borneo, also with bi-coloured legs but clearly not belonging to Alienostreptus due to the position of ventral soft pads on male legs, is documented based on photographs.

The majority of species of the subfamily Rhynchoproctinae is distributed in southern China, Myanmar, Thailand, Laos, Cambodia and Vietnam. A few species are distributed in Borneo, Malacca Peninsula, Sumatra, Sunda Islands and as far south as Lombok.
Until now, only two species in two genera of Rhynchoproctinae have been reported from Vietnam, viz, Alienostreptus alienus (Attems, 1936) and Uriunceustreptus uniserialis (Attems, 1938). Based on new material from Vietnam, we describe a new colourful giant millipede, the second species of the genus Alienostreptus. The present study provides a new diagnosis of the genus in order to include the new species.
Several photographs of a superfi cially very similar species from Borneo exist, but no specimen has been available. The Bornean species is strikingly similar to the new species from Vietnam. However, the colour of the legs is slightly diff erent, and the position of the ventral soft pads on male legs is also diff erent. We, therefore, regard the Bornean specimens as belonging to a genus diff erent from Alienostreptus.

Material and Methods
Specimens were examined from the following collections: NHMW = Naturhistorisches Museum Wien, Vienna, Austria RBINS = Royal Belgian Institute of Natural Sciences, Brussels, Belgium ZMUM = Zoological Museum, State University of Moscow, Russia The morphological terminology follows previously published papers (Pimvichai et al. 2009(Pimvichai et al. , 2010. Living specimens were photographed with a digital camera. Measurements and photographs were made with a Nikon DS-Fi2 camera mounted on a Nikon SMZ25 stereo microscope, using the NIS-Elements Microscope Imaging Software with an Extended Depth of Focus (EDF) and edited in Adobe Photoshop CS6.
Gonopods drawings were performed with pencil and then black liners using a Olympus SZ-61 stereo microscope, sketches were scanned with a CanoScan Lide 60 scanner and then edited with Corel Photo-Paint X5 software. Figure plates were assembled in Adobe Photoshop CS6.

Gonopod terminology
We use the following terminology for the gonopod structure of the genus Alienostreptus (terms not in Pimvichai et al. 2010 in bold): as = additional spine: an additional spine on the telopodite, diff erent from femoral spine (fe) and tibial spine (ti) ac = anterior coxal fold: the main part of the gonopod as seen in anterior view. Confusingly called posterior coxal fold by Demange (1961) and Hoff man (1975) ca = canopy of anterior coxal fold: the canopy-like apical part of the anterior coxal fold in some species fe = femoral spine: a spine originating slightly distal to the point where the telopodite is fl exed ('knee') or where the telopodite emerges from the coxa fl = fl ap: a mesal, lamellar process of posterior coxal fold (pc) lr = lateralmost ridge: lateralmost ridge of posterior coxal fold (pc) mr = mesal ridge: mesal ridge of posterior coxal fold (pc) pc = posterior coxal fold: the main part of the gonopod as seen in posterior view, much shorter than anterior coxal fold (ac) px = paracoxite: the basal, lateral part of the posterior coxal fold sp = setalike spines: apical processes on the solenomere, slender, pale, soft ti = tibial spine: a long spine on the telopodite, originating distal to the femoral spine, at the basis of the apical part of the telopodite tp = triangular process: a pointed triangular process of lateralmost ridge (lr) of posterior coxal fold (pc) tr = transverse ridges: transverse ridges across the outer surface of the solenomere Apical part = the distalmost part of the telopodite
In the morphology-based phylogeny of Rhynchoproctinae by Pimvichai et al. (2010), Alienostreptus comes out in the middle of a paraphyletic sequence of one-genus branches, between Balustreptus Hoff man, 1980, and Winklerostreptus Demange, 1969. Phenetically, Alienostreptus is most similar to Balustreptus, sharing a series of transverse ridges across the apical part of the telopodite, presence of more than one spine on gonopod telopodites, presence of tarsal pads covering the entire ventral surface only on tibia of walking legs, and an unmodifi ed collum. From Balustreptus, Alienostreptus diff ers, i.e., by having two 'femoral' spines on the gonopods as well as having the apical part of the telopodite broadly expanded. Pimvichai et al. (2010) diagnosed the genus Alienostroptus based on one species, viz, Alienostreptus alienus (Attems, 1936). Here, we revise the genus diagnosis to accommodate the new species (characters changed from Pimvichai et al. 2010

in bold):
A genus of Rhynchoproctinae. Collum narrowed laterally, ends rounded-truncate, with strong anterolateral marginal groove and ridge; stipes of mandibles with a ventral abruptly narrowed swollen lobe; coxae of the seventh pair of legs unmodifi ed; ventral soft pads only on tibiae on all legs except fi rst two pairs; epiproct with a projection; hypoproct completely fused with epiproct. Gonopod sternum (st) absent; fl ap (fl ) tongue-shaped, thin, projecting caudad from mesal margin of coxa; femoral spine long, duplicated (fe); apical part of telopodite broadly expanded, with several strong transverse ridges (tr) across outer surface, apically with a row of pale spines (sp). (Attems, 1936) Figs 1

Notes
See Attems (1936) and Pimvichai et al. (2010) for the full description of this species. The gonopods of A. alienus were fully illustrated (Pimvichai et al. 2010: fi g. 5). Here, we document the syntype of A. alienus housed in NHMW, also for comparison with the new species (Fig. 1).

Diagnosis
Diff ers from the only other species in the genus, A. alienus, by: -larger size -straight preanal process (epiproct) -tip of anterior coxal fold (ac) forming a fl attened, sickle-shaped lamella with serrate margins -canopy of anterior coxal fold (ca) with a broad, rounded lobe (in A. alienus with serrate margins) -apical part of telopodite forming a single broadly expanded sheet, in A. alienus ending in two branches -tibial spine much shorter than in A. alienus

Etymology
The species epithet refers to the strikingly bi-coloured legs.
M . Stipes with disto-posterior lobe, ventral side of lobe thickened, with pale, soft area. G . Stipites distally with ovoid, poorly sclerotized, hairless area in middle of which small sclerotized 'island' carries one single spine-like seta. C (Fig. 3A). Lateral lobe anteriorly with large, smooth, rounded, protruding extension; posteriorly with rectangular corner and several wrinkles.

Ecology
Alienostreptus bicoloripes sp. nov. is found in a mixed tropical forest, formed mainly by broadleaf trees with tree ferns (Cyathea Sm. sp. and others) (Fig. 6A-D). At Kon Chu Rang Nature Reserve, adults were active in the daytime as well as at night. Juveniles were hiding all the time. Adults were distributed over a wide range of habitats, from the very bottom of valleys to the dry ridges with coniferous forest, which is not very typical of millipedes. The second visit to the Kon Chu Rang Nature Reserve was almost one and a half months earlier than the fi rst one (26 March-6 April 2018), in early spring, and it was obviously the peak of this species' abundance. Numerous juveniles were observed along the streams in valleys (Fig. 2D). They mainly occupy a very specifi c habitat avoided by all other millipedes, viz, soaking wet clumps of leaf litter at the edge of streams and rivers, and also a surrounding area with a gradually decreasing water content. Leaf litter clumps caught by stones in streams also appeared as a habitat for juveniles. Sometimes they occupy troughs formed by rotten fallen trees next to the stream, which also contain a thick layer of wet leaf litter. Juveniles form loose aggregations in certain patches. They spend a few days in one spot, eating leaf litter and accumulating excrement in a ʻchamberʼ, then leave the ʻchamberʼ and move to another spot. Juveniles may be resistant to acute fl ooding as the leaves they inhabit are already soaking wet, and after frequent rains, the water level rises and covers most of the habitat. Three juveniles of later stages were found roaming around on leaf litter near the stream.
At Kon Plong protected forest, Kon Tum Province, Vietnam, (14°43′ N, 108°18′ E, 1050 m a.s.l.), we have not collected specimens due to technical issues. Adult specimens of A. bicoloripes sp. nov. were found exclusively on the surface of leaf litter on hill slopes above streams. Some were eating mushrooms, others roaming.
Specimens from Borneo are not available. However, despite the unusual colour pattern shared with A. bicoloripes sp. nov., it is clear that it belongs to a diff erent genus, based on the presence of ventral soft pads on the postfemora of the male legs.

Discussion
The millipede subfamily Rhynchoproctinae currently comprises 36 species in 14 genera. As mentioned in Pimvichai et al. (2010), members of the subfamily form a monophyletic group by sharing three synapomorphic characters. However, the genus Alienostreptus diff ers from all other genera in the subfamily by having the femoral spine duplicated.
The photographed Bornean specimens (Fig. 7) show a similar colour pattern to that of the type specimens of Alienostreptus bicoloripes sp. nov., but there are diff erences in some details (see above). In the pet trade, there is a millipede looking similar to the Bornean specimens, it is sometimes referred to as

Borneo specimens
A. bicoloripes sp. nov. from Vietnam Body colour brown to dark brown dark brown (almost black) Antennae pink bi-coloured (as legs) Legs from coxae to postfemora pink, tibiae and tarsi yellow from coxae to postfemora brownish orange, tibiae and tarsi pale yellow Ventral soft pads present on both postfemora and tibiae present only on tibiae  Jeekel (2006). Many of the descriptions include notes on leg colour, but only for two species the description more or less reminds of A. bicoloripes sp. nov. These are two species of the endemic Bornean genus Lamellostreptus Demange, 1961: Lamellostreptus complexus (Chamberlin, 1921), described from "Sarawak, Poak, near Kuching": "Legs and antennae pale ferrugineous, with the fi rst two articles darker, brownish" (Chamberlin 1921: 63).
With the reservation that the descriptions of these (and other Bornean) species were based on preserved specimens, this suggests that the Bornean ʻcopycatʼ of Alienostreptus bicoloripes sp. nov. may be a species of Lamellostreptus, subfamily Harpagophorinae. In order to establish the identity of the Bornean species with certainty, a study of a male specimen is, however, needed.
Many tropical millipedes have pronounced seasonal diff erences in activity, often the males come out fi rst, and then females arrive into the community. Males also disappear fi rst, so at the end of the species' season, there are mainly females in the community.
Diff erent areas have diff erent climatic features, so the millipede communities at Kon Plong and Kon Chu Rang have a diff erent timing of seasonal abundance, but for Kon Chu Rang we can assume that early spring is the peak season of A. bicoloripes sp. nov., with a fast decline in abundance over a few months until the absolute absence of adults.
The body colour changes with the age of the millipede. If juveniles are pale beige with yellowish legs, more mature stages acquire a darker brown colour with pronounced yellow legs and antennae, and then adults get the fi nal coaly black body with bright yellow legs and antennae fading into red basally. At one point, there were at least three distinct age stages present in the community: juvenile medium size, juvenile later stage and adults. Juveniles of very fi rst stages were not found. Based on this, we can assume that the life cycle of this species takes at least three years: two years of development and then one as an adult.
The striking colour pattern invites considerations about function. One possibility is that the colours are aposematic. However, living individuals of A. bicoloripes sp. nov. are not very willing to secrete their defensive fl uids -only when placed in alcohol, they start excreting. The ʻwarningʼ may therefore refer to the particularly strong cuticle of A. bicoloripes sp. nov., rather than the chemical defence. At Cat Tien National Park in South Vietnam, many remnants of another harpagophorid, Thyropygus carli Attems, 1938, were found in mammalian excrements, but remnants of A. bicoloripes sp. nov. were never found in this substrate. Finally, a mimetic function cannot be excluded; although an obvious mimetic model has not been observed in Vietnam, the long colourful legs might suggest a scolopendrid centipede. In any case, the similarity of the colour patterns of A. bicoloripes sp. nov. and the so far unidentifi ed, but most probably not congeneric Bornean species, is remarkable.