Formicinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Additional images: queen, face view (small, large)
Costa Rica, Panama (type locality), Colombia, Guyana. Costa Rica: lowland rainforests of both Atlantic and Pacific slopes; I have also found them in the moist forest of Maritza Biological Station of the Guanacaste Conservation Area, but not in lowland dry forest.
Face smooth, with abundant short erect setae and sparse appressed pubescence; scapes surpass vertex margin by length of first funicular segment; pronotum and mesonotum each with pair of dorsal setae; first gastral tergite with sparse appressed pubescence, about two erect setae, not including posterior row; metanotal groove weakly impressed; color orange with darker gaster; queen small, head width across eyes about 0.48mm.
This species is a very common arboreal ant in lowland rainforests. It is frequent in highly insolated habitats, such as the upper canopy and open second growth areas. At La Selva Biological Station it occurred in 11 of 51 canopy fogging samples, suggesting it has a patchy distribution in the forest, but where it occurs it is very abundant, forming large polydomous and polygynous colonies that are spread through entire tree crowns. The nests are in many small superficial cavities: under small epiphytes, in thin dead stems, and under loose bark. I rarely find them nesting in larger cavities. For example, a 2cm diameter rotten stick in the canopy might have a Pseudomyrmex or Camponotus nest in the hollow core, but these Brachymyrmex will be nesting in small chambers under loose bark near the surface. Although they are rainforest ants, they can tolerate the very hottest and driest parts of the habitat. The small nests usually contain multiple dealate queens, and alate queens are also common. They may nest opportunistically in ant plants; I have found them in myrmecophytic Tillandsia bulbosa in the canopy, in Cordia alliodora nodes, and in foliar pouches of myrmecophytic Melastomataceae near ground level.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.email@example.com
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