Dolichoderus brevithorax

Believed to be a herdsmen species, little is known about the biology of .

Identification
Dill (2002) - A member of the Dolichoderus cuspidatus species group. Dolichoderus brevithorax is morphologically very close to Dolichoderus cuspidatus and, especially, to Dolichoderus furcifer of which it originally has been described as a subspecies. These three species belong to a taxonomically difficult complex of partly sympatric, partly allopatric populations that are very variable in many diagnostic characters and form morphological clines (see also discussion of D. cuspidatus). In this context, the low number of available brevithorax series from only two locations is especially problematic. However, on the basis of the examined material, brevithorax can be distinctly separated from all other furcifer or cuspidatus material by its very short and blunt mesonotal spines (86: MSLI). Like furcifer, brevithorax can additionally be distinguished from most cuspidatus populations by its very plump propodeal spines and the straightly or convexly shaped dorsal margin of the petiolar scale. Yet, there are some Bornean populations of cuspidatus that are clinal in these characters.

Nevertheless, the sympatric or parapatric populations from Sumatra seem to be easily and unequivocally distinguishable. The sympatric cuspidatus is always characterized by much longer and more slender mesonotal spines and more slender propodeal spines as well as a deeply concave margin of the petiole. Even furcifer still has longer (absolute: MSL [88], MSW; relative to body size: MSLI [87], MSWI) and more slender mesonotal spines. Additionally, furcifer can be distinguished by its relatively plump propodeum (PpWminl, 87), its more distinctly developed pronotal “shoulders”, the outline of the head (posterior margin of head more concave, outline in full face view more heart-shaped), and is usually larger. The other diagnostic differences between brevithorax and furcifer stated by Menozzi in the first description of the subspecies, such as colour, sculpturing, shorter alitrunk segments, or straight declivitous face of propodeum could not be confirmed.

In conclusion, brevithorax can clearly be distinguished from cuspidatus and furcifer by the very short spines. The remaining differences to furcifer seem to be rather weak and are characters that usually are subject to considerable variation. Nevertheless, the encountered morphological difference, combined with the sympatric or at least parapatric distribution of the three forms, seem to justify the elevation of brevithorax to species status at the moment. Yet, since the low number of currently available series prevents an assessment of the geographical variability of either brevithorax or furcifer, future synonymy with furcifer can not be ruled out. Regarding the development of the alitrunk spines brevithorax links the completely unarmed species, previously grouped into the subgenus Hypoclinea Mayr, with the species of the former subgenus Karawajewella Donisthorpe with their long and pointed spines.

Distribution
North Sumatra (Medan).

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

Nomenclature

 *  brevithorax. Dolichoderus furcifer subsp. brevithorax Menozzi, 1928b: 2, fig. 3 (w.) INDONESIA (Sumatra). Raised to species: Dill, 2002: 32.

Worker
Dill (2002) - Lectotype in brackets: HL 1.22-1.39 [1.33]; HW 1.25-1.45 [1.29]; EL 0.28-0.32 [0.29]; SL 1.18-1.28 [1.24]; AL 1.70-1.98 [1.88]; PnW 0.86-0.98 [0.90]; MWmin 0.30-0.39 [0.37]; MH 0.37-0.49 [0.42]; MSW 0.45-0.51 [0.51]; MSL 0.24-0.28 [0.27]; PpL 0.63-0.86 [0.63]; PpW 0.56-0.67 [0.63]; PpWmin 0.32-0.35 [0.35]; PpH 0.71-0.82 [0.82]; PpSW 0.41-0.49 [0.451; PtW 0.41-0.50 [0.47]; TL 5.06-5.98 [5.43]. Indices: CI 97- 104 [97]; OI 22-24 [23]; SI 86-97 [95]; MSLI 18-22 [21]; MSWI 32-39 [39]; PpSWI 31-35 [35]; PpWminI 24-28 [27]; (n = 11).

Head: Dark-brown to black, scape brown; very finely and densely reticulate-punctate (= micro-imbricate), sometimes with scattered pit-shaped punctation; slightly shining; densely covered by bright yellow pubescence; without pilosity. Head suboval, posterior margin shallowly concavely e marginate, no superoccipital pits.

Alitrunk: Black; very finely reticulate-punctate (= micro-imbricate), partly (e. g. dorsally on pronotum, mesonotum, and propodeum) rugose; matt; scattered pubescent, somewhat more densely on sides of pronotum; only few scattered erect hairs, on ventral side of alitrunk and coxae. Dorsal face of pronotum flat to shallowly concave, its lateral delimination and the anterior “shoulder” corners ± rounded and weakly developed. Mesonotum bearing a pair of short, blunt spines that point upward; in full face view, spines not distinctly larger than propodeal spines; mesonotal spines not higher than the basal portion of mesonotum. Propodeum also dorsally expanded in to a pair of relatively short and plump, blunt spines that are inclined slightly back and sideward. Propodeal spines in shape and size quite similar to those of mesonotum; declivitous face of propodeum matt.

Petiolus: Scale medium-brown, finely reticulate-punctate and pubescent; dorsal margin of scale entire, ranging from straight (type series) to convex (material from Kota-Dah-Pang-Mop).

Gaster: Medium-brown (basal portion of 1st tergite) to dark-brown; very finely reticulate with dense, brightly yellowish pubescence, only sternites and tip of gaster scarcely pilose.

Type Material
Dill (2002) - Syntype workers, Sumatra, Medan (Fullmek) [examined]. One syntype worker here designated as Lectotype (IEGG).