A new species of the genus Castoponera (Araneae, Corinnidae) from Sarawak, Borneo, with comparison to a related species

Abstract A new species of the genus Castoponera Deeleman-Reinhold, 2001, Castoponera christae sp. n., is described here. The species is closely related to Castoponera lecythus Deeleman-Reinhold, 2001, but can be distinguished by the structures of the male palp and the female genitalia.

Our group has conducted several investigations in Borneo to reveal the association between ant-mimicking spiders and ants. Although the Corinnidae fauna in Southeast Asia has been comprehensively reviewed by Deeleman-Reinhold (1993, 2001, our investigations have resulted in the discovery of an undescribed corinnid species. We here describe it, in comparison with the closely related species, C. lecythus.

Materials and methods
Specimens examined here were collected from the forest floors in Danum Valley Field Centre, Tawau Hills Park and Poring Hot Spring, Sabah, and Lambir Hills National Park, Sarawak, Borneo (Fig. 1). Collected spiders were preserved in 75% ethanol. The morphology was examined using a Nikon SMZ1270 microscope, and specimens were sorted and identified on the basis of descriptions in Deeleman-Reinhold (2001). Multi-focused montage images were produced using Helicon Focus ver. 4.2.9 from several series of source images. The habitus images were obtained using a Canon EOS 60D camera with a Canon MP-E 65mm macro lens and the images of the male palp and female genitalia were obtained by the same camera attached to a Nikon AZ100 microscope.
Methodology and terminology for the description follow Deeleman-Reinhold (2001). The leg spination of each segment is described as a row of spines from proximal to distal parts on each side (dorsal, ventral, prolateral and retrolateral sides). However, recognition of spine position on distal part of metatarsi III and IV was very difficult due to the narrow segments. For the distal spines on these segments the total number of spines is given, without positional information. For the width of the eye region, the width of posterior eye row was measured. All measurements are given in millimeters. Abbreviations used in the present paper are as follows: ALE, anterior lateral eyes; AME, anterior median eyes; d, dorsal; pl, prolateral; PLE, posterior lateral eyes; PME, posterior median eyes; rl, retrolateral; v, ventral.
Coloration and setation (Figs 2-4). Carapace dark brown, covered with short fine setae; anterior surface near eye region covered with white plumose setae. Chelicera brown; anterior surface sparsely covered with long gray setae and short transparent setae; promargin of fang furrow densely fringed with long thick setae whose surfaces are rough (Fig. 5). Labium, maxilla, sternum brown. Legs covered with black setae, black plumose setae and transparent plumose setae; plumose setae sparse in tarsi; coxae I, II and III brownish cream; coxa III more darker than I and II; coxa IV brown; trochanters almost same coloration as in coxae; femora light brown, tinged with black in femora I, II and III; patellae yellowish cream to brownish cream; tibiae I and II grayish yellow, III and IV light brown; metatarsi almost same coloration as in tibiae; tarsus I cream, tarsi II and III brownish cream, tarsus IV light brown. Pedicel dark brown. Abdomen blackish brown; entire surface covered with white fine plumose setae, posterior surface additionally covered with long setae; thick white plumose setae forming following markings: a pair of patches and transverse band on anterior dorsum, transverse band encircling abdominal constriction, two or three patches and transverse band on posterior dorsum; posterior end bearing tuft of white long plumose setae.
Coloration and setation. Almost same as in male. Etymology. The specific epithet is a patronym in honor of Dr. Christa L. Deeleman-Reinhold, who has made great contributions in studies of corinnid spiders from Southeast Asia.
Distribution. Lambir Hills National Park, Sarawak. Remarks. For the female paratype, some morphological characters of the abdomen were not observed because the specimen had once been dried and the soft part of the abdomen was shrunken. However, the sclerotized parts of the abdomen and the genitalia have been well preserved and the identification is possible on the basis of these characters.
Castoponera christae sp. n. is closely related to C. lecythus. The male of C. christae sp. n. can be distinguished from the male of C. lecythus by the medially constricted abdomen (Figs 2-4 vs. Figs 19-21), shape of apical part of the bulb and route of the sperm duct running on the surface of the bulb (Figs 6-7, 15-16 vs. Figs 23-24, 32-33). Additionally, among our specimens of each species, the posterior bulb of C. christae sp. n. is more swollen than that of C. lecythus. In the females it is relatively difficult to distinguish the species using superficial characters. However, the internal genitalic structures are clearly distinct (Figs 14, 18 vs. Figs 31, 35). Male . Carapace oval, with granulated surface (Fig. 19). Chelicera with three promarginal and two retromarginal teeth on fang furrow (Fig. 22). Retrocoxal hymen obviously smaller than ALE, approximately 0.05 mm in diameter. Pedicel wrapped in tube-like sclerite extending from abdomen (Figs 19-21). Abdomen slender oval, slightly constricted at anterior part; entire surface strongly sclerotized (Fig. 20).
Coloration and setation (Figs 19-22). Carapace dark brown, covered with short fine setae; anterior surface near eye region covered with white plumose setae. Chelicera brown; anterior surface sparsely covered with long gray setae and transparent plumose setae; promargin of fang furrow densely fringed with long thick setae whose surfaces are rough (Fig. 22). Labium, maxilla, sternum brown. Legs covered with black setae, black plumose setae and transparent plumose setae; plumose setae sparse in tarsi; coxae I, II and III brownish cream; coxa III darker than I and II; coxa IV brown; trochanters almost same coloration as in coxae; femora brown; patellae I and II yellowish brown, III and IV light brown; tibiae I and II yellowish brown, III light brown, IV brown; metatarsi almost same coloration as in tibiae; tarsi yellowish brown, IV more darker than others. Pedicel dark brown. Abdomen blackish brown; entire surface covered with plumose setae, some white and some light brown, and posterior surface covered with long setae; thick white plumose setae forming following markings: transverse band on anterior dorsum, transverse band encircling middle part, large patch on posterior dorsum; posterior end bearing tuft of long white plumose setae. Female . Almost same as in male, except for abdomen. Abdomen without distinct constriction; anterior half covered with strongly sclerotized surface .
Coloration and setation (Figs 26-29   Remarks. We examined 1 male and 1 female collected from the type locality, and these specimens agreed with the original description of C. lecythus. For the comparison with C. christae sp. n., see Diagnosis and Remarks in C. christae sp. n.

Notes on C. christae sp. n. and C. lecythus
The members of Castianeirinae are considered to be myrmecomorphies (Cushing 1997;Deeleman-Reinhold 2001). In the fields, C. christae sp. n. or C. lecythus occur sympatrically with Ponerinae ants such as Diacamma Mayr, Odontoponera Mayr and Leptogenys Roger. These ants might be the suitable models of Batesian mimicry for C. christae sp. n. and C. lecythus because they are common and abundant in the forest floor, and have a sting. Castoponera christae sp. n. and C. lecythus are especially similar to Diacamma spp. in the coloration and setation of the abdomen (Figs 36-37). The transversal bands of white setae on the abdomen emphasize the similarity to Diacamma ants.
Haddad and Dr. Jeremy Miller for helpful comments on the manuscript. We also thank the staff of the Institute for Tropical Biology and Conservation (UMS), the Danum Valley Management Committee, the Danum Valley Field Centre, SFC and SFD for all their help and support. The study was supported by JSPS KAKENHI Grant Number 16657028, 19570094, 24570109, 14J04245, JSPS International Training Program (ITP, Kagoshima University) and Sumitomo Foundation Grant for Basic Science Research Projects No. 130648.