Acromyrmex octospinosus

Identification
Median pronotal spines usually present and distinct, occasionally reduced or absent; head tapering behind eyes; head width less than or equal to 1.7 mm.

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil, Ecuador, French Guiana, Guatemala, Guyana, Honduras, Mexico, Suriname, Trinidad and Tobago, Venezuela.

Biology
Longino (| Ants of Costa Rica):

Acromyrmex coronatus is a montane species found in cloud forest habitats and not in the lowlands. It is tolerant of cold, wet conditions and colonies can be found in small clearings and gaps in dense cloud forest. On the transect on the north side of Volcan Barva it has been found at 1100m elevation but not at 500m or 2000m. On the Central Valley side it has been collected at 1600m elevation at Zurqui. In the Monteverde area it occurs in the community area, up to the highest ridges at 1700m, and down to 800m in the Penas Blancas Valley.

In Monteverde, it is the main pest in gardens and will come into houses at night to cut bread, cabbage, or fruit that has been left out. The nests are often in or under a piece of dead wood, and often with a superstructure of loose dead leaf fragments. They do not excavate soil very extensively if at all. They may be arboreal at times, nesting in a low branch junctions of epiphyte-laden trees.

Lisa Ellis, an undergraduate student with the University of California Education Abroad Program in the late 1980's, carried out a study of A. coronatus foraging during the transition from dry to wet season in Monteverde. She found that foraging was continuous at night, but diurnal foraging only occurred when there had been recent rain. Following a heavy rain, diurnal foraging would commmence followed by a gradual cessation over a period of a day or two. Periodic rains during the dry season would initiate a short bout of diurnal foraging, but when the rains became more continuous diurnal foraging became continuous. Thus the lack of diurnal foraging during the dry season was a short-term response to immediate environmental conditions and not a long-term change in colony foraging behavior.

Nuptial flights are common in Monteverde and the distinctively-patterned dealate queens are often seen on the roads. On 9 July 1984 I observed a swarm of males in the canopy of an emergent oak on the ridge crest above Monteverde. Hundreds of males were swarming just above the highest branches of the tree. Later in the day I saw many dealate queens on the roads.

I have observed aggregations of founding queens under epiphyte mats in recent treefalls. Several times I have seen dealate queens out cutting leaves, suggesting that queens need to forage themselves to establish a colony.

Nomenclature

 *  octospinosus. Formica octospinosa Reich, 1793: 132 (w.) FRENCH GUIANA. Forel, 1893e: 590 (s.q.m.); Wheeler, G.C. 1949: 674 (l.); Wheeler, G.C. & Wheeler, J. 1986d: 496 (l.). Combination in Atta: Emery, 1892b: 163; in Atta (Acromyrmex): Forel, 1893e: 590; in Acromyrmex: Mann, 1916: 454. Senior synonym of guentheri: Emery, 1894c: 220; of pallida Crawley: Wheeler, W.M. 1937c: 70. See also: Gonçalves, 1961: 157. Current subspecies: nominal plus cubanus, ekchuah, inti.
 * guentheri. Atta (Acromyrmex) guentheri Forel, 1893e: 594 (s.w.q.m.) TRINIDAD. Junior synonym of octospinosus: Emery, 1894c: 220.
 * pallida. Acromyrmex octospinosa var. pallida Crawley, 1921: 92 (s.w.) GUYANA. [Unresolved junior secondary homonym of Oecodoma pallida Smith, above.] Junior synonym of octospinosus: Wheeler, W.M. 1937c: 70.