Dolichoderus pilinomas

The rather sparse biological data indicate a typical herdsmen lifestyle. D. pilinomas is associated with the allomyrmococcine Borneococcus bauensis. These mealybugs are extensively carried about by the workers and are kept within the bivouac-like nest. The single found colony was very small and monogynous. (Dill 2002)

Identification
Dill (2002) - A member of the Dolichoderus cuspidatus species group. Morphologically, D. pilinomas occupies a special position within the Dolichoderus cuspidatus group. The workers of pilinomas differ from all other species of the group in the presence of erect hairs on the dorsal face of the body. Regarding this character as well as the relatively small body size, the workers of pilinomas appear to be morphologically intermediate between the cuspidatus and the Dolichoderus thoracicus species groups (see discussion of the respective species groups). However, the morphology of the sexual castes strongly suggest that this species belongs to the cuspidatus group: the queen is apterous with a fused mesonotum, its pilosity is extremely sparse, and its petiolus scale is very wide; the males, in contrast to the workers but in correspondence with the males of the other species of the group, are completely void of erect hairs, and have the large eyes and long mandibles which are typical for the species group. Furthermore, the biological data (monogyny, association with and transport of an Allomyrmococcini partner species, nesting behaviour) strongly indicate a herdsmen lifestyle, and thus, further support the placement of this species into the cuspidatus group.

While the workers differ from all other known species of the cuspidatus group in the presence of dorsal pilosity. They can be distinguished from the hitherto described workers of the thoracicus group by the relatively massive and high rising propodeum. Except for the dorsal pilosity, pilnomas is morphologically closest to Dolichoderus pastorulus. This is particularly true regarding the body size, the sculpturing or head and alitrunk, the shape of pronotum and mesonotum, and particularly the shape of the high rising propodeum, although the latter is even more distinctly developed in Dolichoderus pastorulus. In addition, both species are similar in having comparatively small colonies. Since all available pilinomas material stems from a single nest series, it is difficult to assess the intraspecific variability.

Distribution
Western Sarawak (Northwestern Borneo).

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia, Malaysia.

Nomenclature

 *  pilinomas. Dolichoderus pilinomas Dill, 2002: 56, figs. III-18, III-25, III-31 (w.q.m.) BORNEO.

Worker
(Holotype in brackets): HL 1.08-1.22 [1.12]; HW 0.98-1.14 [1.06]; EL 0.25-0.32 [0.28]; SL 1.00-1.10 [1.06]; AL 1.50-1.72 [1.59]; PnW 0.67-0.76 [0.71]; ML 0.37-0.51 [0.41]; MW 0.29-0.36 [0.31]; PpL 0.59-0.71 [0.63]; PpW 0.52-0.61 [0.55]; PpH 0.58-0.67 [0.63]; PpSW 0.39-0.49 [0.43]; PtW 0.35-0.45 [0.39]. Indices: CI 89-95 [95]; OI 25-31 [27]; SI 93-104 [100]; MI 120-156 [131]; PpSPpI 69-85 [79]; (n = 30).

Head: Medium-brown to dark-brown; evenly, densely and finely punctate (= micro-imbricate), matt; with fine, silverish pubescence; pilose, but longest erect hairs not longer than eye width; scape with sparse short erect hairs. Head slightly longer than wide, sides rounded, occipital margin emarginate.

Alitrunk: Reddish-brown to medium-brown; finely reticulate to finely punctate (= micro-imbricate), mesopleuron additionally with coarser, longitudinal wrinkles; weakly shiny; sparsely to densely pubescent; pronotum and mesonotum pilose; on propodeum, erect hairs restricted to upper half of the ascending dorsal face. Dorsal face of pronotum, in profile, ± straight, its lateral delimination rounded, not edged, shoulders indistinct; mesonotum forming a rounded, medially impressed hump, its posterior portion flattened; coni form processes of mesopleuron distinctly developed; propodeum relatively large and high, in profile, distinctly overtopping mesonotum, almost as high as long (fig. III-18b); ascending dorsal face of propodeum posteriorly broadened, its corners laterally somewhat expanded to blunt tips (fig. III-18d); declivitous face, in profile, slightly concave, but posterior margin of ascending face not or only slightly overhanging.

Petiole: Medium-brown; sparsely pi lose and pubescent; very finely reticulate, shining; upper margin of scale ± straight, not or only very weakly emarginate.

Gaster: Tergites anteriorly reddish-brown to medium-brown, posteriorly dark -brown; finely reticulate to finely punctate, slightly shining; ± densely, golden to silverish pubescent, erect hairs on tergites and sternites.

Queen
HL 1.29; HW 1.25; EL 0.34; SL 1.14; AL 1.81; PnW 0.96; ML 0.90; MW 0.68; PpL 0.76; PpW 0.82; PpH 0.82; PpSW 0.55; PtW 0.71; TL 6.33. Indices: CI 97; OI 27; SI 91; MI 133; (n = 1).

Shape, coloration, sculpturing and pubescence of head as in workers; frons and vertex densely covered with erect hairs (profile view), but sides and scape hardly pilose (full face view); three small ocelli present. Alitrunk apterous with fused mesonotum, but deliminations of scutum and scutellum region still recognizable by coloration and shallow furrows; in profile, shallow impression between scutum and scutellum region; vestigial wing buds present; propodeum massive, but less strongly ascending than in workers, hardly overtopping the mesonotum; posterior margin of ascending dorsal face of propodeum somewhat impressed, its corners distinct but hardly expanded laterally; declivity in profile slightly convex but not curved forwards. Entire alitrunk densely pubescent; erect hairs very sparse, only few single hairs on mesonotum and anterior margin of pronotum (figs. III-25b-c); sculpturing as in workers, but lacking the coarser wrinkles on mesopleuron; erect hairs all legs much more sparse and shorter than in workers. Petiole densely pubescent, lacking erect hairs; scale large and wide, almost as wide as propodeum (fig. III-35b). Gaster ± evenly blackish-brown, its tergites lacking the typical bicoloured “stripes”; densely pubescent, erect hairs restricted to ventral face and tip.

Male
HL 0.82; HW 1.04; EL 0.50; EW 0.37; SL 0.28 ; CL 0.26; MdL 0.44; AL 1.59; ML 1.04; SeW 0.78; PtW 0.37. Indices: CI 126; OI 48; SI 26; (n = 1).

Typical Dolichoderus males with the characters typical for the cuspidatus group. Head brownish-black, mandibles and antennae yellowish-brown, alitrunk, petiole, and gaster yellow-brown to castaneous, coxae, femora, and tarsi yellow, tibiae brown. Sculpturing and pubescence as in workers, but erect hairs completely lacking. Eyes very large, mandibles long (fig. III-31a); wings hyaline and pubescent.

Type Material
Hololype worker, 5 paratype workers (BMNH), 1 paratype female (BMNH), 1 paralype male (BMNH), 3 paratype workers , 3 paratype workers , 6 paratype workers (FNMS), all from same nest series: Borneo, W-Sarawak, 1st Division, Gua Kapur (Fairy Cave), 8 km SW Bau, 1°22'N, 110°8' E. 15.vi.1994 (M. Dill).

References based on Global Ant Biodiversity Informatics

 * Dill M. 2002. Taxonomy of the migrating herdsmen species of the genus Dolichoderus Lund, 1831, with remarks on the systematics of other southeast-Asian Dolichoderus. Pp. 17-113 in: Dill, M.; Williams, D. J.; Maschwitz, U. 2002. Herdsmen ants and their mealybug partners. Abhandlungen der Senckenbergischen Naturforschenden Gesellschaft 557: 1-373.
 * Pfeiffer M.; Mezger, D.; Hosoishi, S.; Bakhtiar, E. Y.; Kohout, R. J. 2011. The Formicidae of Borneo (Insecta: Hymenoptera): a preliminary species list. Asian Myrmecology 4:9-58