Colobostruma froggatti

These ants form small colonies with less than 100 workers in forested sites ranging from wet to dry sclerophyll. Nests have been found in cracks in rocks with moss covering.

Identification
This species is recognisable by the 6-segmented antenna with a distinct subbasal lobe, the relatively elongate, narrow mandibles and the anteriorly converging ridge above the eye. It is most similar to Colobostruma papulata but differs in the shape of the ocular ridge, which diverges anteriorly in papulata (Shattuck 2000).

Key to Australian Colobostruma Species

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  froggatti. Epopostruma froggatti Forel, 1913g: 177, pl. 2, figs. 3, 4 (w.) AUSTRALIA. Combination in Alistruma: Brown, 1948e: 117; in Colobostruma: Taylor & Brown, D.R. 1985: 60. See also: Shattuck, in Bolton, 2000: 42.

Shattuck (2000) - The specimens here considered to belong to froggatti show considerable variation in sculpturing and, to a lesser extent, overall body size. The nature of the sculpturing is similar in all specimens but its development varies. Specimens from Western Australia generally have more strongly developed and distinctive sculpturing on the dorsal surfaces of the head, alitrunk, petiole and postpetiole compared to specimens from the eastern states. Size also varies, with some of the South Australian specimens averaging smaller. In most other respects these specimens are essentially the same. Given the limited amount of material and its wide geographic distribution, it is difficult to evaluate this variation in a meaningful way. While it is likely that more than one species is involved, the currently available material does not allow their diagnosis with confidence and a conservative approach is taken, treating this material as representing a single taxon.

Worker
Shattuck (2000) - TL 2.5 - 3.2, HL 0.66 - 0.77, HW 0.58 - 0.67, C I 87 - 94, ML 0.20 - 0.25, MI 29 - 36, SL 0.30 - 0.33, SI 47 - 52, PW 0.31 - 0.41, AL 0.64 - 0.82 (5 measured). Anterior region of head flat, weakly separated from posterior regions by a slight concavity, not obviously phragmotic. Ridges immediately in front of eyes straight, converging anteriorly. Frontal lobes and lateral margins of clypeus smooth relative to the surrounding surface of the head. Mandibles relatively thin and elongate, their outer margins weakly concave. Hairs absent from dorsum of head. Posterior margin of head moderately to deeply concave. Antenna with 6 segments. Scape elbowed and with a well developed subbasal lobe. In dorsal view the widest point of the pronotum is at the humeral angles. Propodeum high, its posterior face approximately the same height as the petiolar node and with broad, thin lamellae; in profile the dorsum of the alitrunk flat anteriorly and flat to weakly convex medially. Lateral postpetiole drawn outwards into thin flange-like wings, the wings with translucent windows along their posterior margins only. First gastral tergite with weak, indistinct sculpturing, superimposed with low, closely spaced carinae on the anterior one-third. Body colour honey yellow to yellow-red, the petiole and postpetiole sometimes slightly darker, the gaster often with an irregular infuscated band across centre of the first tergite.