Dolichoderus cuspidatus

Maschwitz & Hanel (1985) initiated the study of herdsmen lifestyle in D. cuspidatus from Peninsular Malaysia. Twelve closely related species mostly from Borneo investigated since (including Dolichoderus erectilobus, Dolichoderus maschwitzi, Dolichoderus pastorulus, Dolichoderus tuberifer) also show typical herdsmen characteristics: obligate association with highly polyphagous Allomyrmococcini mealybugs (Malaicoccus, Dicranococcus, Borneococcus), strongly developed transport of mealybugs, freely exposed bivouac nests. Colonies have a single ergatoid queen and over 10000 workers (Dill 2002). Diurnal. Heterick & Kitching (2022) collected this species in the canopy of a lowland dipterocarp forest in Brunei.

Identification
Dill (2002) - A member of the Dolichoderus cuspidatus species group. Together with Dolichoderus furcifer and Dolichoderus brevithorax, cuspidatus forms a taxonomically difficult complex. These three species are distinct from the other species of the cuspidatus group particularly by the presence of a pair of spines each on the mesonotum and the propodeum. The three species are morphologically closest to Dolichoderus coniger and Dolichoderus magnipastor which not only have very similar propodeal spines, but also share a number of other characters such as the shape of head and petiolus. Yet, coniger and magnipastor do not bear spines on the mesonotum.

While this complex is easily distinguishable from the remaining species of the species group, it is difficult to define clear diagnostic deliminations of the species within the complex. The examined populations of the complex that has a wide area of distribution including Peninsular Malaysia, Sumatra, and Borneo, display a high variation in many diagnostic characters. The often mosaic-like distribution and the sometimes clinal transition of these characters make a clear diagnosis problematical.

While some characters such as colour and body size vary considerably even within the same nest, there are other characters that are relatively homogenous within one nest series or one location but differ distinctly between different populations. Such characters that may be interpreted as an indication for isolation and speciation are, for instance, the development of the mesonotal and propodeal spines, the shape of the petiolar scale, the surface sculpturing (particularly of the head), and the relative width of the propodeum (PpWminI). Yet, especially among the Bornean populations these characters are distributed in a mosaic-like pattern.

Notwithstanding the complex situation of the Bornean cuspidatus populations, it is possible to separate clearly all cuspidatus specimens from furcifer and brevithorax. D. furcifer is distinct by its propodeum which is very wide in relation to the body (PpWminI > 27), while brevithorax is clearly separable by its extremely short and plump mesonotal spines (MSL 0.24-0.27; MSLI 18-21) (see fig. III-86). In addition, there are further differences between brevithorax and furcifer on the one hand and at least the sympatric or parapatric Sumatran populations of cuspidatus on the other hand: both brevithorax and furcifer have shorter mesonotal spines (fig. III-88), plumper propodeal spines, and the apical margin of their petiole scale is not concave. While these diagnostic characters work well for Sumatra, there may occur clinal transitions and overlaps in certain Bornean populations of cuspidatus.

Also, in the remaining material grouped here as cuspidatus, more or less distinct morphological differences can be found between different populations. Thus, it may be possible that cuspidatus herein very broadly defined actually comprises several good species.

Distribution
Dill (2002) - Peninsular Malaysia, Sumatra, Borneo. Occurring from the lowlands to moderate mountain altitudes (highest 1,150m).

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

Biology
Colonies are monogynous with tens of thousands of workers (Maschwitz & Hänel 1985)

Dill (2002) - Herdsmen ants Dolichoderus cuspidatus cultivate honeydew-producing pseudococcids of the morphologically anomalous tribe Allomyrmococcini. As true migrating nomads the ants move their livestock to fresh, nutrition-rich pastures using a variety of transport techniques. The tight interdependence of the mutualistic partners has led to many behavioural and morphological adaptations, e. g. the complete loss of firm nest structures in favour of flexible bivouac nests (which also give shelter to part of the mealybug colony), well-organized colony relocations towards newly colonized pasture sites of the mealybugs, fission as the mode of colony reproduction to ensure the uninterrupted persistence of the symbiosis, or various behavioural patterns and morphological structures that facilitate mealybug transport.

The morphologically very homogeneous populations of Peninsular Malaysia and Sumatra, as well as the populations of Eastern Sarawak (which are most similar to the Malay-Sumatran populations, e. g. regarding spine length), are all associated with Malaicoccus species, while the remaining Bornean populations are found with other allomyrmococcine genera.

Castes
Queens are ergatoid and usually physogastric throughout the cuspidatus-group (Dill 2002). Elsewhere in the genus Dolichoderus (130 species), ergatoid queens are only known in Dolichoderus doriae.

Nomenclature

 *  cuspidatus. Polyrhachis cuspidatus Smith, F. 1857a: 63 (w.) BORNEO. Forel, 1913k: 88 (m.); Dill, 2002: 35 (q.). Combination in Hypoclinea: Mayr, 1870b: 955 (in key); in Dolichoderus: Forel, 1878: 382; in D. (Hypoclinea): Emery, 1894c: 229; in D. (Diabolus): Wheeler, W.M. 1935c: 68. Senior synonym of surbecki (and its junior synonym bifurcatus): Chapman & Capco, 1951: 181; of atra, tenuispina: Dill, 2002: 35. See also: Shattuck, 1994: 47.
 * tenuispina. Dolichoderus (Hypoclinea) cuspidatus subsp. tenuispina Viehmeyer, 1922: 214 (w.) BORNEO. Junior synonym of cuspidatus: Dill, 2002: 35.
 * surbecki. Dolichoderus (Hypoclinea) cuspidatus st. surbecki Santschi, 1925f: 92 (w.) INDONESIA (Sumatra). Combination in D. (Diabolus): Wheeler, W.M. 1935c: 68. Senior synonym of bifurcatus: Wheeler, W.M. 1935c: 68. Junior synonym of cuspidatus: Chapman & Capco, 1951: 181.
 * bifurcatus. Dolichoderus (Diabolus) bifurcatus Karavaiev, 1926d: 425, fig. 3A (w.) WEST MALAYSIA. Junior synonym of surbecki: Wheeler, W.M. 1935c: 68.
 * atra. Dolichoderus cuspidatus var atra Menozzi, 1930a: 3 (w.) INDONESIA (Sumatra). Subspecies of cuspidatus: Shattuck, 1994: 47; of furcifer: Menozzi, 1932d: 6; Bolton, 1995b: 172. Junior synonym of cuspidatus: Dill, 2002: 35.

Worker
Dill (2002) - (Syntypes in brackets): HL 1.12-1.58 [1.20-1.28]; HW 1.12-1.67 [1.24-1.25]; EL 0.22-0.38 [0.31-0.33]; SL 1.12-1.41 [1.20- 1.22]; AL 1.75-2.28 [1. 88- 1.9I]; PnW 0.83-1.15 [0.88-0.90]; MWmin 0.22-0.53 [0.27-0.30]; MH 0.38-0.96 [0.52-0.53]; MSW 0.50-1.88 [0.57]; MSL 0.32-1.04 [0.38-0.39]; PpL 0.69-1.00 [0.75-0.78]; PpW 0.57-0.78 [0.64]; PpWmin 0.22-0.42 [0.29-0.30]; PpH 0.73-1.02 [0.75-0.76]; PpSW 0.38-0.76 [0.44-0.45]; PtW 0.35-0.68 [0.49-0.50]; TL 4.73-6.49 [5.03-5.13]. Indices: CI 93-109 [98-103]; OI 15-27 [25-27]; SI 91-105 [97]; MSLI 25-71 [31]; MSWI 38-136 [45]; PpSW1 30-50 [35 -36]; PpWminl 18-27 [23-25]; (n=417).

Head: From yellowish-, reddish- and medium-brown to black (types), antennae and clypeus often lighter; very finely reticulate to punctate (types) (= micro-imbricate, fig. III-58); strongly or slightly (types) shiny or matt; in addition to the fine sculpturing often with scattered shallow pits containing one pubescence (very shallow in types); pubescence short, silverish, mostly sparse, but dense on antennae; without erect hairs. Head about as long as wide, sub-oval to rounded heart shaped with convex sides, occipital margin broadly concavely emarginate, often with lateral, shallow, pit-like depressions (very shallow in types), rarely with median superoccipilal pit (very weakly developed in types).

Alitrunk: From yellowish, reddish-, medium and dark-brown to black (types), coxa and femur mostly lighter; very finely reticulate to punctate (= micro-imbricate), on sides of propodeum “meshes” or punctures of fine sculpture often arranged in dense rows, resulting in a fingerprint-like pattern; matt (types) or shiny; mesonotum, mesopleuron, and dorsal face of propodeum often with coarser wrinkles; silverish pubescence; erect hairs only on ventral face of alitrunk and coxae. Dorsal face of pronotum with distinct anterior and lateral delimination, pronotum “shoulders” distinctly developed; mesonotum armed with a pair of ± pointed spines that are very variable in thickness, length and angle (see fig. III-6); cone-like process on anterior margin of mesopleuron usually distinctly developed; propodeum high rising, its corners expanded to a pair of slightly curved spines, the tips of which often spatulately broadened; shape and length of these propodeal spines variable (figs. III-5a-j).

Petiole: From reddish- to medium-brown (types) to black; finely reticulate or punctate; pubescence silverish. Scale, in profile, tapering off apically with the posterior face slightly kinked; apical margin of scale mostly ± strongly emarginate (types), depth and width or the concave arc variable, rarely apical margin straight (figs. III-5k-v); lateral corners of apical margin broadly (types) or slenderly expanded.

Gaster: From reddish- to medium-brown to black, base of first tergite usually lighter yellow-brown to reddish-brown, often with yellow dots; finely reticulate or punctate, slightly shiny; mostly with dense white-greyish pubescence; erect hairs only sparsely present on gaster tip and sternites.

Queen
Dill (2002) - HL 1.37-1.47; HW 1.41-1.65; EL 0.32-0.36; SL 1.24-1.29; AL 2.31-2.50; PnW 1.12-1.22; ML 0.92-1.00; MW 0.80-0.94; MH 0.45-0.55; PpL 0.82-0.94; PpW 0.85-0.96; PpH 0.78-0.98; PpSW 0.45-0.63; PtW 0.76-0.90; TL 7.19-8.55. Indices: CI 103- 11 5; 0 1 2 1-25; SI 76-88; MI 104- 11 7; PpSPpl 52-67; (n = 7).

Colour and sculpturing similar to workers, except even alitrunk lacking coarser wrinkles and pubescence denser on entire body; erect hairs restricted to ventral side and gaster tip. Head slightly wider than long, posterior margin less distinctly concave than in workers. Development of ocelli very variable, ranging from three well developed ocelli to almost complete reduction. Lateral delimination of dorsal face of pronotum ± distinctly angular; alitrunk larger than in workers, but scutum, scutellum, and prescutellum fused to mesonotum, although scutellar region sometimes remains ± distinct; always primarily wingless, but sometimes vestigial wing buds or tegulae present (figs. III-69b-c); mesonotum highly vaulted; instead of the worker's spines, forming a two rounded humps. Propodeum less ascending than in workers, its dorso-lateral corners expanded to short, bluntly coniform processes (sometimes only developed as small points) that are inclined upward and slightly backward, but always much shorter and plumper than the worker's propodeal spines. Scale of petiolus very wide, apical margin straight or concave. Physogastric, i. e. gaster usually very distended.

Male
Dill (2002) - HL 0.95-1.02; HW 1.16-1.24; EL 0.59-0.65; EW 0.41-0.48; SL 0.35-0.41; MdL 0.38-0.47; CpL 0.27-0.33; AL 2.03-2.16; PnW 1.02-1.22; ML 1.37-1.51; MW 0.96-1.14; MH 0.34-0.53; PpL 0.67-0.73; PpH 0.65-0.80; PtW 0.41-0.43; TL 4.28-5.38. Indices: CI 118-128; OI 50-52; OI2 60-66; OI3 35-39; OI4 42-49; MdI 40-48; MdCpI 128-150; SI 30-33; MI 128-147; (n = 6).

Typical Dolichoderus males. Colour and sculpturing similar to workers, except for the lack of coarser rugose areas; erect hairs restricted to the ventral face of petiole and gaster and the genitalia; densely covered by a fine, yellowish pubescence. Head wider than long; eyes very large; mandibles very long; often a pair of shallow, lateral, pit-like depressions near the occipital margin. Alitrunk, petiole, and gaster similar to other males of the cuspidatus group; neither spines nor coni form processes on mesonotum or propodeum.

Type Material
Polyrhachis cuspidatus

Two worker syntypes in. Labelled “SAR.”

Determination Clarifications
Dill (2002) - Franz (1975b: 265) lists “D. (Diabolus) cuspidatus F. Sm.” in a survey of Javanese forest ants as “rarely occuring in Bogar, 250 m, in forest, nesting between leaves and in hollow trunks”. The list is based upon the collections made by H. H. F. Hamann (Linz, Austria). Yet, in Hamann’s collection, which completely is in OOLM, there is no material of cuspidatus. Thus, Hamann’s cuspidatus identification could not be confirmed. Since cuspidatus has never again been reported from the otherwise relatively well collected island of Java, the identification remains doubtful.

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