Acanthomyrmex mindanao

Found nesting in logs on the ground, Acanthomyrmex mindanao has small colonies of less than 50 workers.

Identification
Moffett (1986) - A member of the notabilis group. Minor Workers: Well developed small projecting lobes immediately on each side of medial hair on anterior margin of clypeus, funicular scrobes present. Major Worker: Postpetiole about as wide as long in dorsal view. Dorsum of head with large fovea.

Postpetiole in both castes approximately cuboidal, not conspicuous­ly wider than deep in dorsal view; pro­podeal spines shorter than in Acanthomyrmex notabilis. Minors with posterior margin of head moderately concave in dorsal view, and with funicular scrobe present, although poorly developed; ventral mandible tooth usually present, and with strongly pro­jecting medial clypeal lobes.

Philippine specimens are very similar to the type series, except for a Momungan major that is smaller (HW 1.64) and hairier than the paratype major. This major also has hypostomal teeth, and lacks a subpetiolar declivity. Ginoog worker specimens consistently lack the pair of hairs near the summit of the petiolar node which are usually present in specimens from other series. Color in a few specimens uniform yellow. Workers of a Sarawak series are the smallest recorded for this genus (HW 0.70 to 0.76 mm) and are significantly smaller than any of the Philippine specimens (HW 0.90 to 1.11 mm). These ants lack a ventral mandibular tooth, lack sublateral hairs on their petioles, and have the pilosity on their postpetioles reduced to two pairs of hairs dorsally and one lateral pair. The larger of the minor workers from the Philippines (HW >  1.05 mm) completely lack pronotal spines. Also, the same individuals have better developed ventral mandibular teeth than in other minors; their gasters are somewhat hairier and they have a more deeply engraved frontal sulcus. They therefore show some characteristics intermediate between the minor and major castes.

Distribution
PHILIPPINES: Lanao del Sur, Mindanao, MSU-Marawi (7°59'58.74N, 124°15'41.36E), 776 m, 24.iv.2010, coll. Malik Nagamora Jr., LSD Mindanao State University

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia, Malaysia, Philippines.

Habitat
Tropical forests

Abundance
Uncommon in collections.

Biology
Assumed majors crush seeds and defend the colony. The minors forage for seeds.

Foraging/Diet
Seeds

Colony Attributes
Small colony size, less than 50 workers.

Nesting Biology
Nest in logs on the ground.

Reproduction
Queens present.

Morphology
Majors have very large robust heads.

Castes
Dimorphic ants with short, stocky majors and spiny minors.


 * Minor Worker

Nomenclature

 *  mindanao. Acanthomyrmex mindanao Moffett, 1986c: 82, figs. 39E, 51-56 (s.w.) PHILIPPINES.

Worker
Minor Holotype (HW 1.05 mm) and four minor paratypes measure HW 0.98 to 1.06, HL 0.84 to 0.91 (CI 114 to 117), ML 0.65 to 0.71 (MI 75 to 78), SL 0.83 to 0.88 (SI 81 to 84), EL 0.19 to 0.22, HFL 0.90 to 0.95 (FLI 104 to 107; FWI 21 to 22) mm. Head in full-face view appearing flattened or slightly concave across poste­rior margin. Head widest above the eyes. Head with oval foveae having thick walls; dorsally the longest hairs extend 0.08 to 0.10 mm. Scrobes bent  sharply  downwards posteriorly, forming a shallow groove for funiculus extending dorsad to each eye alongside groove for scape. Scapes relatively short (SI < 90), so that when retracted to scrobes, scapes barely extend beyond back margin of head. Mandibles often with relatively few den­ticles (usually eight or less; eight to 12 in most specimens in other species). Clypeal index 129 to 134. Lobe to each side of medial clypeal hair strongly produced, and more approximate  to hair  than  in  other species; lateral clypeal hairs not in a com­pletely enclosed fovea. Smooth medial area of clypeus not bordered laterally by dis­tinct rugae. Mandibles with a tiny but dis­tinct ventral tooth. Spines on trunk short relative to other species, propodeal  spines  conspicuously longer than pronotal spines, and are vir­tually straight to feebly curved caudad; pronotal spines very short and stubby (lacking in larger minor workers in some other series: see below). Pronotal spines without conspicuous hairs. Pronotal angle never drawn out into a feeble tooth. Pro­podeal declivity bordered on each side by one rugum or possibly two adjacent rugae (second rugum poorly developed when present). Node of petiole as in Figure 39E, PWI narrow (45 to 64); caudal  face of  node usually with a pair of hairs near summit (absent in Fig. 56), in addition to the sin­gle pair found lower on the same face of node in this and most other Acanthomyr­mex. Anterior peduncle of petiole rela­tively short and deep as in A. notabilis, and with lateral petiolar hairs present (but sometimes hair missing from one side of petiole); sublateral pair lacking. Subpetio­lar declivity present. Postpetiole subrec­ tangular, almost as long as it is wide in dorsal view, and with two or three longi­tudinal rugae on each side; hairy dorsally. Femora only with basal hairs or having one to three additional hairs, and with ventral surfaces distinctly concave; hind femora relatively short (FLI < llO). Or­ange yellow to reddish orange, with legs lighter yellow.

Major Paratype  measures  HW  1.98, HL 2.16 (Cl 92), SL 0.90 (SI 46), EL 0.26, HFL 1.00 (FLI 46; FWI 20) mm. Foveae on head smaller and shallower than in A. notabilis (somewhat larger and denser be­neath head), numerous except very few present in area between antennal scrobes. Pilosity present on head, but more scat­tered than in A. notabilis majors. Cephal­ic hollow conspicuous. A darkly pigmented streak extends to hollow from dorsum of head; wide medial sulcus conspicuous from hollow to frontal area. Forward margin of clypeus with a medial projec­tion. Hypostomal teeth absent. Propodeal spines short and curved caudad. Color as in minor workers, but head a richer or­ange, antennae a contrasting shade of yel­low.

Type Material
Holotype 1 minor. Paratypes: 4 minors and 1 major deposited in the Harvard University Museum of Comparative Zoology. Mindanao, Davao Province, east slope of Mt. McKinley, 3,300 feet, lot 33, under bark, 30 August 1946 (F.G. Werner)

Etymology
The specific name is a noun in apposition after the type locality