| Genus List | Species List | Key to Workers |

The genus Tapinoma

This genus escapes notice by most people, even though they are ubiquitous and widespread. Workers are all very small, less than 3mm long. To the beginning myrmecologist they can cause consternation because they are obviously ants but appear to lack a petiole. Close inspection reveals that the petiole is present, just very small and lacking a dorsal node, and largely hidden by the gaster. Workers have a uniform and rather simple habitus. The cuticle is thin, generally unsculptured, and there are never spines or tubercles of any kind. Conspicuous erect setae are almost always lacking (one Costa Rican species has a pair of setae on the pronotum).

Foraging workers are not conspicuous. They rarely occur in large aggregations, and instead are most often seen as scattered individuals darting over surfaces. They have a rapid and erratic motion.

Costa Rica's fauna consists of one pantropical tramp, T. melanocephalum, and several arboreal species. The tramp species is most often found in dwellings and highly disturbed habitats. The native species forage and nest in the vegetation. Workers are rare in forest floor leaf litter, although they are more likely to occur in leaf litter in dry forest.

Colonies are often polygynous and polydomous, so it can be difficult to assess the size of entire colonies, but individual nests are usually small, with tens to hundreds of workers.

Nests of most species are in preformed plant cavities. These may be thin dead sticks, under bits of loose bark, in preformed cavities in live stems, in and under epiphyte mats, and in bromeliad bases. One species, T. ramulorum inrectum, makes small carton nests under leaves.

Taxonomically it is very difficult to define species boundaries. The combination of small size, lack of pronounced surface features, and tendancy to collapse or otherwise deform on drying contribute to their general neglect by myrmecologists.

On various occasions I have attempted to divide Costa Rican material into morphospecies by simple visual inspection. This has generally been a frustrating exercise and the genus is still wide open for serious taxonomic work. For the current purposes I have developed a crude taxonomy that separates a few conspicuous species and leaves two highly variable entities that are most likely aggregates of species.

Literature Cited

Page author:

John T. Longino, The Evergreen State College, Olympia WA 98505 USA.longinoj@evergreen.edu

Date of this version: 23 October 2006.
Go back to top

Go to Ants of Costa Rica Homepage