Pheidole fallax Mayr 1870

Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia

worker face view

worker lateral view

major face view

major lateral view


Widespread in the Neotropics from Costa Rica to Argentina, and on many Caribbean islands. Costa Rica: common in northwest (dry forest habitats); also in Coto banana plantation in southwest.


Minor worker: head length 0.76mm, head width 0.63mm, scape length 0.94mm, Webers length 1.01mm (n=1). In full face view, posterior margin of vertex evenly rounded; no vertex collar; promesonotal and metanotal grooves well impressed; propodeal spines of moderate length; face smooth and shining; pronotum smooth and shining, usually with a few transverse rugae at anterior margin; mesonotum foveolate laterally, more weakly sculptured dorsally, shiny, smooth or with a few transverse rugae; propodeum foveolate laterally and dorsally, but dorsal sculpture weaker; gaster smooth and shiny; dorsal pilosity moderately abundant, long, flexuous; color red brown.

Major worker: head length 1.87mm, head width 1.71mm, scape length 0.94mm (n=1). Face entirely and strongly punctatorugose; scape base grossly thickened, abruptly bent, with large basal flange covering condyle; hypostomal margin lacking median or paired teeth typical of many other species, but recessed teeth flanking inner margin of mandible are large, triangular, conspicuous; head, mesosoma, and gaster with abundant, moderate length, somewhat stiffened, amber-colored, erect setae, including abundant short erect setae projecting from sides of head in face view.

fallax is a complex lineage with the nominal plus eleven subspecies in the taxonomic literature (none of them with type localities in Costa Rica).

Natural History

This is a common dry forest species in northwest Costa Rica. Colonies can occur in very open, disturbed areas. For example, they have been observed in the central city park of Liberia, and in banana plantations at Coto. Workers are seed harvesters, and form conspicuous trunk trails to seed sources. They are also generalist foragers and will readily come to baits. Diurnal and nocturnal foraging have been observed. The nests are in bare soil, with conspicuous nest entrances and chaff piles. Workers have a foetid odor when collected. In Santa Rosa National Park, Longino once observed a colony emigration: a thick column of alate queens and brood-carrying workers extended many meters along the edge of a dirt road.

Page authors:

John T. Longino, The Evergreen State College, Olympia WA 98505 USA.

Stefan Cover, Museum of Comparative Zoology, Harvard University, Cambridge MA 02138 USA.

Date of this version: 4 December 1997
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