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Labidus of Costa Rica

The genus Labidus is part of the subfamily Ecitoninae, which is comprised of the New World army ants. All known species are nomadic group raiders. Morphologically the subfamily is characterized by having a distinct postpetiole (workers only); eyes absent or composed of at most a single ommatidium (in large workers the ommatidium can be fairly large, but is clearly composed of a single facet); and antennal sockets fully exposed with surrounding semicircular ridges. Workers are weakly to strongly polymorphic.

Ecitonine males are robust insects with elongate, cylindrical abdomens, and are often encountered at lights. They are strong fliers, and superficially resemble wasps. When captured and held in one's fingers, they make probing motions with the abdomen, as though imitating stinging motions of vespid wasps. They have large and heavily sclerotized genitalia, which are taxonomically useful for distinguishing genera and species. Queens are permanently wingless, always remain in colonies (reproduction is by colony fission), and are rarely seen.

The last synthetic revision of the New World army ants was Borgmeier (1955). This is a large work, in German, with over 700 text pages and 87 plates of figures. Watkins ((1976) provided a useful synopsis, with species lists, English translations of the keys, distribution maps, and compressed versions of the figures. Additional information on army ants can be found at Gordon and Roy Snelling's army ant pages, a site dedicated to New World army ants.

In Costa Rica there are four genera of army ants: Eciton, Labidus, Neivamyrmex, and Nomamyrmex. Labidus can be distinguished from all others, in the worker caste, by the combination of (1) toothed tarsal claws, and (2) propodeum with dorsal face smothly rounding into posterior face, with no teeth or flanges. Labidus exhibits strong polymorphism, with strikingly enlarged soldiers with allometrically enlarged heads, but they never have the sickle-shaped mandibles of Eciton soldiers.

Literature Cited

Borgmeier, T. 1955. Die Wanderameisen der neotropischen Region. Studia Entomologica 3:1-720.

Watkins, J. F., II. 1976. The identification and distribution of New World army ants (Dorylinae: Formicidae). Baylor University Press, Waco, Texas.

Page author: John T. Longino longinoj@evergreen.edu

Date of this version: 18 July 2005.

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