Formicinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Range
Costa Rica to Colombia. Costa Rica: throughout the country below 500m elevation.
Identification
Minor worker: Propodeum lacking spines or tubercles of any kind; propodeum somewhat box-like, dorsal and lateral faces flat or nearly flat and meeting at an approximate right angle; dorsal face of propodeum subrectangular; pubescence on first gastral tergite dilute, appressed to suberect, not obscuring integument; color black; propodeum not strongly projecting, forming part of continuous dorsal profile of mesosoma; in face view with relatively abundant erect setae projecting from sides of head, from mandibular insertions to level of eyes; erect setae on first gastral tergite relatively long (shorter on senex); dorsal and posterior faces of propodeum meeting at relatively shallow angle.
At La Selva Biological Station the pubescence on the scapes is more appressed on brevis than senex, but the scape pubescence on senex is variable elsewhere in the country. In particular, it is more appressed on the Pacific side of Costa Rica.
Similar species: senex.
Natural History
This species is one of the most common in lowland Costa Rica. It is very abundant in the Pacific lowlands and the southern Atlantic lowlands (e.g. Hitoy Cerere Biological Reserve) but is relatively less abundant in the northern Atlantic lowlands (e.g. La Selva Biological Station and vicinity). It prefers low, scrubby vegetation and is rarely found in mature forest. Workers are diurnal. Nests are almost always in small dead stems that are in low vegetation or even on the ground in open areas. The exception was one nest I observed in a live internode of a Cecropia sapling at a pasture edge. The habitat preference of C. brevis is revealed at La Selva Biological Station, where it has been collected once by manual search at ground level in a disturbed area, and once in a Malaise trap, yet has not occurred in 52 canopy fogging samples.
In Corcovado, I observed a nest in a dead Cassia stem that was immediately adjacent to a large carton nest of an Azteca colony. Thus the species is not excluded by Azteca, and may even benefit by nesting near them. It would be worth investigating whether they share foraging trails with Azteca.
Notes
Minor workers seem to always have very dilute pubescence on the gaster. On the Atlantic side of Costa Rica major workers have gastral pubescence like minor workers, but on the Pacific side they have more abundant appressed pubescence, contrasting with the minor workers.
Literature Cited
Forel, A. 1899. Biologia Centrali-Americana; or, contributions to the knowledge of the fauna and flora of Mexico and Central America. Insecta. Hymenoptera. 3 (Formicidae). London. 169 pp.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA.longinoj@evergreen.edu
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