Leptogenys pusilla (Emery 1890)

Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia

worker face view

worker lateral view

worker face view

worker lateral view

Upper images of worker; lower of queen.


Costa Rica (type locality) to Panama. Costa Rica: wet forest lowlands throughout the country (Hitoy Cerere Biological Reserve, La Selva Biological Station, Rio Penas Blancas Valley at 800m, Carara Biological Reserve, Osa Peninsula, San Vito).


In usual resting position, mandibles flush against anterior border of clypeus; clypeus large and triangular, completely concealing labrum; head subrectangular in frontal view; median clypeal lobe longer than basal width, apex acutely pointed; face smooth and shining; scapes relatively short; first and second funicular segments relatively short, little longer than wide (relatively longer in josephi); eye weakly convex, distance between eye and mandibular insertion greater than ocular diameter; mesonotum 4 times wider than long in dorsal view; petiolar node trapezoidal in dorsal view, anterior margin convex and at least half the width of posterior margin; petiolar node subcuboidal in lateral view, with distinct vertical anterior and posterior faces; petiole relatively high and short in lateral profile (longer in josephi).

Worker metrics (n=4). HL (0.72-0.87); HW (0.47-0.50); ML (0.28-0.35); EL (0.08-0.15); SL (0.53-0.75); PW (0.42-0.48); WL (0.94-1.22); PH (0.37-0.45); PL (0.37-0.48); DPW (0.27-0.27) mm. CI (0.58-0.65); MI (0.61-0.70); OI (0.18-0.30); SI (1.14-1.50).

Similar species: josephi.

Natural History

This species occurs in moist to wet forested areas, ranging from secondary to primary forest or cocoa plantations. Nests have been found in decomposing wood on the ground. One specimen has a mite on the apical internal side of the metatibia. Specimens are most often from Winkler samples of sifted leaf litter. Dana Meyer, a student working at Sirena in Corcovado National Park, collected a live colony from under a rotten log and observed it for a period of time. His notes indicated that the colony (1) took small isopods but not small flies; (2) was possibly polygynous; and (3) had lighter-colored ergatoid queens.


This ant is very similar to L. josephi but L. pusillus is a smaller ant, compared with L. josephi (WL 1.20-1.34mm), and its head is not as elongate in appearance. Emery (1894:49) published L. pusilla as a new species for the second time. Queen morphology is similar to the worker, but with a striking difference in possessing greatly swollen yellow mandibles, with convex internal and external margins. The function of the modified mandibles can only be guessed at presently. Such mandibles are also known for the queens of the apparently closely related species from northern South America, L. ritae. Interestingly in L. ritae, there are also queens with normal mandibles.

Type data

Lobopelta pusilla Emery 1890:43. Syntype worker: Costa Rica, Jimenez (Alfaro).

Literature Cited

Emery, C. 1890. Studii sulle formiche della fauna neotropica. Bull. Soc. Entomol. Ital. 22:38-80.

MacKay, W. P. and E. E. MacKay. 2004. A new species of the ant genus Leptogenys (Hymenoptera: Formicidae) with inflated mandibles. Sociobiology 43:255-258.

Page authors:
John E. Lattke piquihuye@gmail.com
John T. Longino longinoj@evergreen.edu

Date of this version: 3 March 2009.
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