Acanthostichus brevicornis

This is the most commonly encountered species of Acanthostichus. It has been found under cow manure together with termites (Bruch, 1924) and is known to be a termite predator (Bruch, 1925). Mann (1916) found a small colony under a deeply imbedded stone.

Identification
A member of the brevicornis species complex. Mackay (1996) - The workers of this species can be distinguished from others in that the femur is very broad, the petiole is subquadrate, usually with a strongly concave anterior face. It can be differentiated from Acanthostichus femoralis and Acanthostichus sanchezorum in that the propodeal spiracle is positioned at the midline, not above midline as in the other two species. It is similar to Acanthostichus kirbyi (and other related species, see discussion of A. kirbyi), from which it can be distinguished as the dorsum of the petiole is often punctate, with elongate depressions, the anterior face is not strongly thickened, the lateral clypeal teeth are poorly developed and the femur is not incrassate in A. kirbyi. The male can usually be distinguished from other species as it has an elongate petiole, is small and is without bluish reflections (see key).

A Paraguay collection differs from the “typical” A. brevicornis in being strongly dimorphic, increasing the range of worker size. Additionally the anterior face of the petiole is nearly straight as seen from above.

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Brazil, French Guiana, Guyana, Paraguay, Suriname.

Biology
Mackay (2004) - A Paraguay collection was found nesting in the soil in grazed second growth vegetation. This species is not uncommon in that collection locality. Alex Wild (personal communication) saw it several times under logs and near the surface of the soil where he was digging. It was always found in disturbed habitats, e.g., grazed areas, lawns, nesting in red clay soil.

Nomenclature



 *  brevicornis. Acanthostichus brevicornis Emery, 1894c: 142 (w.) FRENCH GUIANA. Mackay, 2004: 98 (q.). Senior synonym of ramosmexiae: Kusnezov, 1962a: 130; Mackay, 1996: 144.
 * ramosmexiae. Acanthostichus ramosmexiae Bruch, 1924b: 260, fig. (w.) ARGENTINA. Bruch, 1925a: 110 (m.l.). Junior synonym of brevicornis: Kusnezov, 1962a: 130; Mackay, 1996: 144.

Worker
Mackay (1996) - HL 0.74-0.96, HW 0.66-0.76, SL 0.31-0.38, WL 1.19-1.24, PW 0.35-0.40, PL 0.36-0.43, SI 39-42, CI 79-90, PI 100-106.

Mandible with only apical tooth developed; anterior medial border of clypeus concave, lateral clypeal teeth poorly developed; frontal carinae poorly developed, closely placed; head elongate, occipital border concave; petiole quadrate, anterior border strongly concave (Fig. 19), subpetiolar process a broadly rounded lobe (Fig. 20); femur flattened and incrassate (Fig. 43). Surface of body smooth and glossy (including scapes, dorsum of meso soma and dorsum of petiole).

Mackay (2004) - Additional measurements (n = 3): HL 0.71-1.07, HW 0.56-0.82, SL 0.30-0.40, SW 0.11-0.18, EL 0.04-0.06, WL 0.92-1.46, PL 0.29-0.47, PW 0.29-0.46, SI 37-42, CI 76-90, PI 100-106, SL/SW 2.20-2.73.

Queen
Mackay (2004) - HL 1.02, HW 1.01, SL 0.43, SW 0.19, EL 0.18, WL 1.67, PL 0.62, PW 0.83, Sl 42, CI 99, PI 50, SL/SW 2.25.

Subdichthadiiform, mandible without teeth (Fig. 6); anterior border of clypeus concave (Fig. 5); frontal carinae closely spaced, posterior border of head concave, sides of head rounded; malar groove poorly developed, extending from base of mandible slightly more than 0.1 mm, remainder of groove marked by very slight indentation; scape thickened; eye large, but failing to reach side of head by about ½ minimum diameter; ocelli absent; mesosoma basically rectangular as seen from side (Fig. 9), and as seen from above; promesonotal suture poorly developed, metanotal suture marked on dorsum of mesosoma; propodeal spiracle placed above midline (Fig. 9), propodeum rounded between faces; subpetiolar process absent (Fig. 9), petiole wider than long as seen from above, slightly wider posteriorly (Fig. 8); posterior femur slightly widened (Fig. 7), much less so than that of worker; pygidium without spines.

Erect hairs sparse; few hairs along anterior border of clypeus, and on mandible, along frontal carina, dorsum of head, posterior margin of head, dorsum of mesosoma, and legs; hairs on posterior face of propodeum fine, brushlike, with similar hairs on side and posterior margin of petiole; ventral surface of petiole with thick, closely spaced hairs; gaster with similar hairs on dorsal and ventral surfaces.

All surfaces smooth and glossy.

Yellow, mandibles and clypeus slightly darker.

Type Material
Mackay (1996) - FRENCH GUIANA: Cayenne [examined]. Calen [?] Jelski; Typus; Acanthostichus parallelus [? Word marked out] brevicornis Em; Typhlomyrmex serratula [label obviously incorrect]