Gauromyrmex

Bolton (2003 p 269) states there are a number of undescribed species in the British Museum. Also: “all known species are arboreal and are size variable to weakly polymorphic.” Most of what is known about the two species are anecdotal reports: Gauromyrmex acanthinus - This ant appears to be rather common in India and China, and I believe that I have seen it on several occasions in Bengal Province nesting under loose bark, though the actual specimens were lost in a wartime shipment. In life, the distinctive point of recognition lies in the extremely depressed appearance of the ant, even when moving about. It appears to the naked eye somewhat like a flattened Leptothorax, and its attachment to tree trunks and plant cavities may be correlated with the habitus. (Brown 1953); Gauromyrmex bengkalisi - The species description states that collections of this ant were made in the forest and their nests were built in “resin trees” (presumably the common species Styrax benzoin).

Identification
Small workers, brown with darker gaster. Similar to Vollenhovia but with 11-segmented antennae and a bidentate propodeum. Vollenhovia possess a 12-segmented antennae and an unarmed, or at most just slightly toothed, propodeum.

Fossils
Fossils are known from: (an unidentified species, Wang et al., 2021).

Biology
Eguchi, Bui and Yamane (2011) - All known species of Gauromyrmex are arboreal (Bolton 2003). Brühl (2003) reported that an undetermined Bornean species used resin to build nests on tree trunks at a height of about 15 to 18 m from the ground. The nests had a grayish, hard surface and were smoothly attached to the bark of the trees. A few tiny holes about one millimetre wide led inside the nest. Within the nest were many hollows and recognizable tunnels. There were between two and four nests of varying sizes on a tree trunk, suggesting a possible polydomous colony structure.

Nomenclature

 *  GAUROMYRMEX [Myrmicinae: Formicoxenini]
 * Gauromyrmex Menozzi, 1933c: 146. Type-species: Gauromyrmex bengkalisi, by monotypy.
 * Gauromyrmex senior synonym of Acalama, Solenomyrma: Brown, 1953c: 10.
 * Gauromyrmex junior synonym of Vollenhovia: Hölldobler & Wilson, 1990: 16; Bolton, 1994: 105.
 * Gauromyrmex revived from synonymy: Bolton, 2003: 246, 269.
 * ACALAMA [junior synonym of Gauromyrmex]
 * Acalama Smith, M.R. 1949a: 206. Type-species: Acalama donisthorpei (junior synonym of Solenomyrma acanthina), by original designation.
 * Acalama junior synonym of Gauromyrmex: Brown, 1953c: 10.
 * SOLENOMYRMA [junior synonym of Gauromyrmex]
 * Solenomyrma Karavaiev, 1935a: 103. Type-species: Solenomyrma acanthina, by monotypy.
 * Solenomyrma junior synonym of Gauromyrmex: Brown, 1953c: 10.

Description
Smith (1949), as Acalama - Worker. Small, apparently monomorphic. Head (including mandibles) subcordate, with rounded posterior corners and not very deep, but distinctly emarginate posterior border. Antenna ll-segmented; with a prominent 3-segmented club, the latter much longer than the remainder of the funiculus; scape short, curved basally, enlarged apically, failing by one-fourth to one-third its length from reaching the posterior border of the head. Frontal carinre short, well-separated, indistinctly or not lobed, concealing antennal insertions. Frontal area indistinct or absent. Clypeus, in profile, flattened, median region extended as a short lobe, the anterior border of which is straight or indistinctly emarginate. Eye well-developed, placed nearer the anterior than the posterior border of the head, with at least 7-9 ommatidia in its greatest length. Mandible of ordinary shape, the masticatory border with 2 large apical and 3 or 4 smaller basal teeth.

Thorax, in profile, flattened or weakly convex. Pronotum with a distinct humeral tooth. Promesonotal suture obsolescent. Mesoepinotum with a remarkably deep constriction. Epinotal spines unusually short, upwardly directed. Legs rather short, with greatly enlarged femora and tibiae; tibial spur of anterior leg well-developed, those of the middle and posterior legs vestigial or lacking. Petiole non-pedunculate; anterior and posterior faces of the node declivous, the two surfaces meeting to form a sharp, transverse carina which is distinctly emarginate; ventral surface of petiole with a tooth. Post-petiole slightly broader than long, also broader than the petiole. Gaster truncate basally, with distinct humeral angles.

Eguchi, Bui and Yamane (2011) - The following description is based on Bolton 2003 with minor modification. Worker variable in size or weakly polymorphic; head in full-face view subrectangular with round posterior corner, in lateral view flattened dorsoventrally; frontal carina and antennal scrobe absent; median portion of clypeus extends anteriorly as a short truncated lobe that overlaps and is closely applied to mandiblar dorsum, anterior margin of lobe shallowly evenly concave, angulate anterolaterally; posteromedian portion of clypeus relatively broadly inserted between frontal lobes; mandible short, with 6 teeth; antenna 11-segmented, with 3-segmented club; eye medium sized; promesonotum very weakly convex dorsally, a little higher than anterior border of propodeum; promesonotal suture absent dorsally; metanotal groove impressed dorsally; propodeal spine triangular; propodeal spiracle positioned high on side, at about midlength of sclerite; middle and hind femora incrassate; petiole in lateral view without distinct anterior peduncle, but with triangular node with dorsolateral corners forming acute angles or denticles, ventral face of petiole with a large process; gastral shoulder present.