Pheidole synarmata Wilson 2003

Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia

worker face view

worker lateral view

major face view

major lateral view


Minor worker: head length 0.53mm, head width 0.53mm, scape length 0.44mm, Webers length 0.61mm (n=1). Head flattened behind, slightly excavate; promesonotum evenly and strongly arched, mesonotal suture absent; propodeal spines short, sharp, upturned; face smooth and shining; katepisternum and dorsal face of propodeum foveolate (very faint on Guyana specimens), rest of mesosoma smooth and shining; pronotum with a transverse anterior carina (like P. laselva); gastral dorsum smooth and shining; dorsal pilosity moderately abundant, medium length, flexuous; color dark red brown to yellow.

Major worker: head length 1.15mm, head width 0.92mm, scape length 0.45mm (n=1). Clypeus smooth and shiny, with small median tubercle between frontal carinae; frontal carinae elevated and projecting anteriorly (the above characters like P. rhinoceros); anterior half of face with longitudinal rugae, interspaces and posterior half of face smooth and shiny; antennal scrobes present in the form of broad, shallow depressions; hypostomal margin flat, with no medial tooth, pair of stout triangular teeth located less than one third distance to recessed teeth flanking mandibles; dorsal pilosity abundant; head with abundant suberect setae projecting from sides of head in face view.

Similar species: subarmata, hasticeps.


Guyana, Colombia, Costa Rica. Costa Rica: Atlantic lowlands (La Selva Biological Station).

Natural History

The types were collected in Kartabo, Guyana, a lowland rainforest site. In Costa Rica the species is known from two collections from La Selva Biological Station, both from samples of sifted leaf litter from the forest floor.


This species is very similar to subarmata. In general the inner hypostomal teeth of the majors are larger on synarmata than subarmata and the antennal scrobe is more developed. Usually the elevated frontal lobes are acute and relatively sharp in synarmata, more broadly rounded in subarmata, but this character shows considerable variation in South American material of subarmata. Majors of both synarmata and subarmata can be distinguished from hasticeps by the lack of a median hypostomal tooth and the presence of a diverging fan of longitudinal carinae on the face posterior to the clypeal triangle. On hasticeps this region is smooth or with a few parallel, non-diverging carinae laterally. Also, the major of hasticeps has the frontal lobes more rounded and less elevated.

Minor workers of synarmata have foveolate katepisternum and dorsal face of proposeum, while subarmata and hasticeps are completely smooth and shining. The propodeal spines of subarmata are absent or extremely small, while the spines of synarmata and hasticeps are more often visible as distinct, albeit small, spines.

Wilson (2003) identified as synarmata specimens from Cuiaba, Mato Grosso (Trager). These are quite different and not the same as synarmata. The frontal carinae of major are triangular and laterally expanded, not upturned.

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: 2 September 2008.
Previous versions of this page: 7 October 2003, 21 March 2007.
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