Revision of Arcastes Baly , 1865 from the Oriental Region ( Coleoptera , Chrysomelidae , Galerucinae )

Th e species of the genus Arcastes Baly, 1865 from Oriental Region are revised. Th e type species is A. biplagiata Baly, 1865 by original designation. Th e genus Arcastes was erected by Baly based on a peculiar shape of the antennae. Subsequently, eight other species have been described in this genus. Up to now this genus was not revised, in particular the male and female genitalia have not yet been studied. Studies of the type material revealed, that A. biplagiata possess a very peculiar shape of median lobe and endophallic structures. Next to the genotype, only two valid species remain in this genus: Arcastes suturalis Jacoby, 1884 (with A. ismaili Mohamedsaid, 2000 as new synonym), and Arcastes dimidiata Laboissière, 1929. Arcastes sumatrensis Jacoby, 1884 is a new junior synonym of Neolepta biplagiata Jacoby, 1884. All other species need to be transferred to other genera that will be subject of the ongoing revision of the Oriental Galerucinae. Distribution of the three species of Arcastes is restricted to Singapore, Malaysia, and Indonesia, southward to Java. In this paper we provide redescriptions of the genus and the valid species, including illustrations of external and genitalic characters, photographs of the primary type specimens, distribution maps and a key.

Baly (1865) and subsequent authors assigned species to Arcastes based on merely external morphological characters, in particular the enlarged third to seventh antennomeres.After checking the genitalic patterns of the species named above and many other oriental "Monoleptites", it became clear that the median lobe has a peculiar outer shape and asymmetric endophallic structures.Both characters are very useful to delimit this genus from others, while enlarged medial antennomeres also occur in some species of Monolepta and Neolepta.
Only three species remain in Arcastes based mainly on characters of the genitalic structures of the type species.Arcastes sumatrensis Jacoby, 1884 is a new junior synonym of Neolepta biplagiata Jacoby, 1884.All other species need to be transferred to other genera that will be subject on the ongoing revision of Oriental Galerucinae.An illustration of external and genitalic characters are presented here for these taxa, photographs of the primary type specimens, distribution maps and a key are also included.

Materials and methods
A standard set of fi gures is given for each species.Th ese include illustrations of the coloration (dorsal view), including the right antenna, where black coloration is indicated by black, yellow coloration by white, red coloration by light grey, and brown by dark grey shading.
Th e antennomeres of males and females, dorsal, ventral and lateral view of the median lobe including the endophallic structures, spermathecae of three females (if available) and bursa-sclerites (if available) usually of one female are fi gured.For the redescription of the genus, illustrations of the pro-, meso-and metathorax, female and male abdomen, right legs in ventral view and of the right hind wing in dorsal view are given.
Measurements were made for external characters.Absolute measurements are: total length from the clypeus to apex of the elytron, length of the elytron, maximal width of both elytra (usually in the middle or posterior third of the elytra), and width of the pronotum.Relative measurements are: length to width of the pronotum, maximal width of both elytra to length of the elytron, length of the second to third antennomer-es, and length of the third to fourth antennomeres.A number of specimens measured is given in the description under "total length".Further materials examined are listed, and all label data are exactly re-written.
Th e subsequent redescriptions are based on labelled specimens from the following collections (Table 1 For location data, geographical coordinates were given in degree and minute.Th ese coordinates were mostly taken from Google Earth.Th e distribution maps have been produced by ArcGis.
Total length.4.45-7.35mm (mean: 5.67) Head.Brownish-red to red.Very fi nely punctuated, with signifi cant transverse impression between posterior third of eyes.Eyes large, strongly convex (Fig. 1).Labial palpi slender and maxillary palpi enlarged, occasionally dark brown to black (Fig. 2a).Labrum pale to dark brown and occasionally blackish in middle.Mandible pale yellow to dark brown and blackish towards apex.Antennae elongated, extended to apical third of elytra (Fig. 1); third to terminal antennomere densely covered by bristle-like setae.First to eighth or ninth antennomeres black, two to three terminal antennomeres contrasting pale yellow to yellowish-brown, only in A. dimidiata two basal antennomeres also yellowish.First antennomere club-shaped, second shortest, third antenno- mere about two times longer than second; ratio length of second to third antennomere 0.50-0.57(mean: 0.54); third to seventh antennomere broad, signifi cantly enlarged, ratio length of third to fourth antennomeres 0.60-0.70(mean: 0.65), eighth to eleventh antennomeres much slenderer (Figs 8,14,20).Th orax.Pronotum transverse, very broad, broadest in middle, anterior angle signifi cantly protruding, posterior angle slightly marked, pronotum with deeply impressed line along lateral margins (Fig. 1).Brownish-red to red as head, shiny, smooth, and fi nely punctuated, without transverse depression.Pronotal width 1.55-2.25 mm (mean: 1.90), ratio length to width 0.48-0.57(mean: 0.53).Scutellum large, triangular, impunctate, brownish, red or black.Procoxal cavities partly open (Fig. 2b).Mesoand metathorax reddish-brown to black.Metasternum broad (Fig. 2c).Elytra elongated, either black throughout, or black with longitudinal yellowish-red spot on disc of each elytron, or black with yellowish to reddish suture that in some species reaches up to one third of each elytron, or basal third completely red and apical two thirds black.Elytra shiny, punctation fi ne, irregular, slightly coarser and denser than that of pronotum.Elytral length 3.80-5.90mm (mean: 4.73), maximum width of both elytra together 1.50-4.00mm (mean: 2.79), ratio of maximum width of both elytra together to length of elytra 0.61-0.72 (mean: 0.66).Alae fully developed (Fig. 4).Legs long and slender, basi-metatarsus elongated (Fig. 5), coxa and trochanter reddish like underside, femur, tibia and tarsus black throughout, tibia with dense and fi ne setae.Abdomen.Pale yellow to reddish-brown, occasionally darker in middle, and seventh sternite usually dark brown to black.Last visible sternite in females rounded at apex, and in males with two deep, parallel-sided incisions (Fig. 3).
Male genitalia.Th e outer shape of median lobe is symmetrical, strongly sclerotized, apex tapered, slightly rounded and not incised.Orifi ce wide, more or less circular to slightly rectangular.Endophallic structures asymmetrically arranged, ventral spiculae hammer-like, median spiculae narrower, slender, lateral spiculae enlarged and slender, with claw-like small spine medially and tube-like, curved spines.Tectum not  Female genitalia.Spermatheca with oval to slender and elongated nodulus.Middle part long and slightly curved, cornu long and curved (Figs 10,16,22).Without stronger sclerotized bursa sclerites.
Distribution.Th e species are restricted to South-East Asia and up to now only recorded from Singapore, Malaysia (Peninsular) and Indonesia (Borneo, Sumatra), southwards to Java (Figs 6,17).
Diagnosis.Beetles of the genus Arcastes are medium sized Galerucinae with strongly elongated basi-metatarsus, without pronotal impressions, reddish head and pronotum and usually contrasting black antennae, legs and elytra, the latter often with yellowish to red spots, suture or base.Th e signifi cantly enlarged third to eighth antennomeres are very characteristic.Arcastes is the most similar to Neolepta Jacoby, 1884, with the type species, Neolepta biplagiata Jacoby, 1884, looking very similar to Arcastes biplagiata at the fi rst glance.Antennae of these beetles are similar with slightly to strongly enlarged antennomeres in the middle, while terminal antennomeres in Neolepta are also black, the basal two antennomeres are reddish, and much slenderer than in Arcastes.Th e dorsal coloration is also similar, but N. biplagiata posses a pale yellowish transverse band or nearly circular spot in the middle of each elytron.Th e genitalic patterns of both sexes possess very strong diff erences.Asymmetric endophallic spiculae of certain shape A. biplagiata (Figs 9,15,21) as in Arcastes are a unique pattern in oriental galerucines with elongated basi-metatarsus, while the median lobe in Neolepta, as in Monolepta, and Candezea, is narrower and has symmetrically arranged endophallic spiculae which are much smaller (cf.Wagner 2001, Wagner andKurtscheid 2005).Th e shape of spermatheca of Arcastes resembles that of Monolepta, but in Arcastes it lacks sclerotized bursa-sclerites, while in Monolepta there are two distinct types of this structure.Also Neolepta and Candeza have strongly sclerotized bursa-sclerites.
Th e pronotum of Arcastes (ratio length to width 0.48-0.57), is on average broader than in Monolepta and Neolepta (0.52-0.65), and within the range of Candezea (0.42-0.59).Procoxal cavities are similarly structured (partly open) in all these genera.Th e third antennomere of Arcastes is roughly twice as long as the second (ratio length of second to third antennomere: 0.50-0.57),which is similar to Candezea (0.49-0.63) but diff erent from Neolepta and Monolepta which both have the second and third antennomere of about equal length (0.82-1.10).While Candezea have strongly elongated, slender antennomeres, Arcastes species can be clearly diff erentiated by the enlarged median ones.
Abdomen.Pale yellow to brown, occasionally darker on middle, last sternite usually dark brown to black.
Male genitalia.Outer shape of median lobe symmetrical, strongly sclerotized, apex tapered and insignifi cantly rounded, not incised.Endophallic structure asymmetrical, ventral spiculae large, hammer-like, median spiculae long, slender, lateral spiculae enlarged, with claw-like small spine medially, only one present.Th ree big spurs located at upper part of endophallic spiculae, most distal one near apex.Tectum not incised at apex, almost reaching apex of median lobe, constricted at middle part and enlarged at base (Fig. 9).
Female genitalia.Spermatheca with slender to oval nodulus.Middle part long and slightly curved, cornu long and curved (Fig. 10).
Diagnosis.Arcastes biplagiata is the most similar in body outline and general coloration to A. suturalis, but the latter has either completely black elytra or a yellowish to yellowish-red spot beyond the scutellum that can be stretched along the entire suture or can be enlarged to a broad reddish sutural band (Figs 11, 12, 13), while A. biplagiata has only elongated spots on the disc of each elytron (Figs 1, 7).Endophallic armature of A. biplagiata is also diff erent from the other two species of this genus (Fig. 9).
Type material.Lectotype: ♂, "Singapore, Baly Coll." (BMNH) (Fig. 7).Type Locality: Singapore, 1°21'N/103°49'E.-Paralectotype: 1 male, same data as lectotype (BMNH).Baly gave no data on the number of specimens in his description.Th ere are at least two specimens available in BMNH, and we herein designate a lectotype to fi x the name on a single specimen.
Further material examined.Indonesia.
Total length.4.70-6.35mm (mean: 5.30, n=12) Head.Reddish-brown to red.Details of mouthparts and impressions on vertex like the description of the genus.Antennae entirely black and only the terminal three antennomeres usually contrasting pale yellow to reddish (Figs 11,12).Shape of antennomeres like the description of the genus.Ratio length of second to third antennomere 0.50-0.57(mean: 0.54), ratio length of third to fourth antennomere 0.67-0.70(mean: 0.68), apical three antennomeres signifi cantly slenderer (Fig 14).
Th orax.Shape and coloration of pronotum and scutellum like in the description of the genus (Figs 11,12,13).Pronotal width 1.55-2.10mm (mean: 1.80 mm), ratio length to width 0.50-0.55(mean: 0.53).Scutellum in about one third of material studied black, others brown, red or yellowish-red.Elytra elongated, black throughout in 35 % of the material examined, about 10 % with yellowish scutellar elytral spot, 50 % with entirely yellowish-red suture, and remaining material with enlarged yellowishred elytral disc like in the specimens of A. ismaili (Fig. 13).Elytral length 3.80-5.05mm (mean: 4.40 mm), maximal width of both elytra together 1.50-3.30mm (mean: 2.40 mm), ratio of maximal width of both elytra together to length of elytra 0.63-0.69(mean: 0.66).Underside and legs like in the description of the genus.
Abdomen.Pale yellow to brown on the sides of sternites, dark brown to black in the middle, terminal sternite usually completely black.
Male genitalia.Th e outer shape as in the description of the genus.Endophallus with three spur located at the upper part, the biggest one next to the lateral spiculae.
Tectum not incised at apex, slender, almost reaching towards the apex of the median lobe (Fig. 15).
Female genitalia.Spermatheca with slender to oval nodulus.Middle part moderately long and slightly curved, cornu long and curved (Fig. 16).
Abdomen.Pale yellow to brown, occasionally darker on middle, and last sternite usually dark brown to black.
Male genitalia.Th e outer shape as in the description of the genus.Endophallus with three spurs located at the upper part, the biggest one next to the lateral spiculae.
Tectum not incised at apex, slender, almost reaching towards the apex of the median lobe (Fig. 21).
Female genitalia.Spermatheca with oval to elongated nodulus.Middle part more less long and slightly curved, cornu long and curved (Fig. 22).
Diagnosis.Arcastes dimidiata can be easily diff erentiated from A. biplagiata and A. suturalis by the elytral coloration.Th e basal elytral third is reddish and strongly contrasting with the black two terminal thirds, while it possess neither a pale suture nor elytral spots (Figs 1,11,18).
). Acronyms used and responsible curators in brackets: Th e Natural

Table 1 .
Numbers of material examined and collections investigated.