Dolichoderinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Additional images:
Queen, mandibles (small, large), petiole, lateral view (small, large), tibia (small, large).
Worker, mandibles (small, large), mandible (small, large), petiole, lateral view (small, large), petiole, ventral view (small, large), petiole, second ventral view (small, large), tibia (small, large).
Syntype worker Azteca schimperi, face view (small, large), lateral view (small, large), mandibles (small, large), labels (large).
Range
Mexico to Argentina. Costa Rica: widespread.
Identification
A member of the A. aurita group.
Queen
Measurements (n=3 queens from Colombia, Brazil, and Paraguay): HLA 1.44 (1.40-1.47), HW 1.05 (1.04-1.06), SL 0.97 (0.94-1.01), CI 72 (71-76), SI 69 (65-69).
Palpal formula 4,3; middle and hind tibia lacking apical spur; apical tooth of mandible about twice as long as penultimate tooth, dorsal surface shiny, smooth, with sparse piligerous puncta; medial clypeal lobe strongly convex and protruding, extending well beyond lateral clypeal lobes; head rectangular, sides parallel and flat, posterolateral margins subangular but rounded, posterior margin a moderately developed V-shaped impression; petiolar node triangular; posteroventral petiolar lobe developed, moderately convex from front to back, laterally compressed and tectiform; scape, sides and posterior margin of head with dense vestiture of short, erect setae; femora with similar setae but erect setae nearly absent from outer margins of middle and hind tibia; pronotum and mesoscutum with these short setae very sparse, more abundant on scutellum and propodeum; petiolar node and ventral margin of petiole with abundant short setae; gaster devoid of erect setae; entire body red brown, with smooth, highly polished and reflective surface.
Worker
Measurements (n=4): HLA 1.42 (1.16-1.51), HW 1.41 (1.18-1.45), SL 0.94 (0.85-1.01), CI 99 (96-102), SI 68 (64-73).
Palpal formula 4,3; middle and hind tibia lacking apical spur; mandible of typical thickness at base, with microareolate sculpture, dull, becoming smooth and shiny, somewhat flattened toward masticatory margin; masticatory margin concave, curving toward enlarged apical tooth, apical tooth much larger than penultimate tooth; medial clypeal lobe strongly convex and protruding, extending well beyond lateral clypeal lobes; head with convex sides, strongly cordate posterior margin; in lateral profile promesonotum forming single convexity, evenly convex to middle of mesonotum, posterior mesonotum drops steeply to depressed basal face of propodeum; petiolar node somewhat pillow-shaped, blunt and weakly bilobed apically, posteroventral lobe shallow, weakly convex from front to back, ending posteriorly in a somewhat abrupt shelf, rising steeply to tergosternal suture, leaving distinct posterior rim on sternite, laterally very strongly compressed, forming sharp median carina (this character less developed on South American material); scape, entire head capsule, mesosoma, legs, petiolar node, and gastral dorsum with appressed pubescence but completely lacking erect setae; color clear yellow orange to red brown, face shining.
Natural History
This species makes large external carton nests. I have observed four nests, three in Costa Rica and one in Panama, and all have been in Cecropia trees (C. peltata, C. obtusifolia, and C. longipes). Benson (1985) also observed A. schimperi in Cecropia trees. However Forel (1908b), describing the queen and male from a collection from Bahia, Brazil, explicitly stated that the carton nest was perched on the branches of a tree that was not Cecropia.
The three nests I have seen in Costa Rica were all at the edges of roads in highly human altered landscapes (pasture edges, coffee farms) in seasonally dry areas. The globular carton nests are very conspicuous on the highly visible branches of Cecropia trees, and in my studies of Cecropia in Costa Rica I always looked for them. Yet I have only seen these three over many years of work in Costa Rica. I have never been able to examine a nest closely, but I have been able to observe the base of the trees in which they occurred. In one case workers were foraging not only on the base of the tree but also on surrounding low vegetation. In another case, on a tree with stump sprouts at the base, workers were swarming over the sprouts but not actually entering the internodes. These observations contrast with typical Cecropia ants, which never forage off the host plant and usually enter and occupy any sprouts at the base of the tree. Thus A. schimperi seems to occupy Cecropia trees more "lightly" than the dominant obligate Cecropia ants.
Azteca schimperi could be a temporary social parasite of Cecropia ants, usurping an existing Azteca colony as a means of establishing its own. Such a scenario might explain the somewhat less specialized use of Cecropia by A. schimperi; it may be a specialist on Cecropia ants rather than Cecropia trees.
Comments
Azteca schimperi has a very broad range, vying with A. alfari for the Azteca species with the largest range. It is a relatively distinctive species with little discernable variation over the range; specimens from Argentina and Paraguay look very like specimens from Central America and Mexico.
See additional discussion of A. aurita group.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
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