Austromorium flavigaster

These ants are general scavengers which nest in the soil, often at the base of trees. They occur in extreme south-eastern Queensland, eastern New South Wales, A.C.T., Victoria, south-east South Australia and south-west Western Australia. Most collections have been from dry sclerophyll with a limited number from mallee.

Identification
Body yellowish-red to reddish-brown, much lighter in colour than A. hetericki, the gaster banded light brown-dark brown-light brown (rather than being dull red with a uniformly coloured gaster), sculpturing areolate-rugose (rather than rugose), dorsal face of propodeum similar in length to posterior face (rather than much longer), propodeal lobes developed as sharp spines (rather than rounded posteriorly), ventral surface of petiole lacks a small tooth anteriorly, and petiolar node with distinct anterior and dorsal faces (rather than having the dorsal and posterior faces forming a continuous surface). In addition, A. flavigaster is much smaller than A. hetericki (head width < 0.85mm vs. head width > 1.30mm).

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 *  flavigaster. Xiphomyrmex flavigaster Clark, 1938: 366, fig. 5 (w.) AUSTRALIA. Combination in Chelaner: Bolton, 1976: 294; in Monomorium: Taylor, 1987b: 2; incertae sedis in Monomorium: Heterick, 2001: 441; in Austromorium: Shatuck, 2009b: 65.

Description
Mandibles triangular, with 4-5 teeth. Palp formula 2,2. Clypeus projecting slightly forward, bicarinate. Frontal lobes narrow but covering antennal insertions, posterior sections converging slightly. Eyes with 8-10 ommatidia in greatest diameter, located laterally on head at the midpoint of its length. Sides and vertex of head flat, connected by a broad, rounded curve. Antennae 12 segmented with a 3-segmented club.

Mesosoma compact. Anterior face of pronotum rising almost vertically from the collar and rounding gradually into the dorsal surface. Mesonotum and dorsal surface of propodeum forming a continuous surface separated by a weak metanotal groove. Dorsal face of propodeum approximately the same length as the posterior face. Propodeal spines well developed. Propodeal lobes developed as sharp spines which are 3/4 the length of the propodeal spines. Propodeal spiracle small, located level with the base of the propodeal spine, approx. 3x its diameter from the posterior propodeal face. Tibial spurs absent from middle and hind legs.

Petiolar peduncle about half as long as petiolar node. Venter of petiole flat anterior and lacking a subpetiolar process; posterior sectioned angled ventrally relative to anterior section. Node with distinct anterior, dorsal and posterior faces, the anterior and dorsal faces approximately the same length, the posterior face much shorter causing the dorsal face to slope rearward. Postpetiole with a low process ventrally. Postpetiolar node with distinct anterior, dorsal and posterior faces, the dorsal face weakly convex.

Mandibles smooth but overlain with weak, low carinae. Head areolate-rugose with the dorsal surface of the head between the eyes tending towards costate. Mesosoma, petiole and postpetiole areolate-rugose. Legs and gaster smooth. Entire body with elongate erect or suberect hairs, those on the scapes and legs shorter and more appressed. Anterior clypeal margin with a row of long, curved setae which extend anteriorly about 1/2 the length of the mandibles.

Colour yellowish-red to reddish-brown, antennae and legs lighter. Gaster generally banded with the anterior section of the first tergite and the terminal segments paler than the posterior section of the first tergite.

Measurements. Worker (n=8): CI 88-96, EI 15-18, EL 0.10-0.14, HL 0.71-0.87, HW 0.65-0.81, ML 0.77-0.99, MTL 0.38-0.47, SI 75-81, SL 0.52-0.62.