Dolichoderinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Additional images:
Queen, mandible (small, large), petiole, lateral view (small, large), tibia (small, large).
Worker, mandible (small, large), petiole, lateral view (small, large), tibia (small, large).
Range
Southern Mexico to Ecuador and west to the Santa Marta region of Colombia. Costa Rica: Pacific lowlands.
Identification
Queen
Measurements (n=5): HLA 1.94 (1.86-1.98), HW 1.59(1.55-1.70), SL 0.96 (0.89-0.98), CI 85 (79-87), SI 49 (48-50).
Palpal formula 5,3; middle and hind tibia with prominent pectinate apical spur; dorsal surface of mandible coarsely punctate, puncta bearing stiff erect setae, mandible appearing bristly; medial and lateral clypeal lobes at about same level; head subrectangular, posterior margin moderately excised medially; petiolar node short, triangular; posteroventral petiolar lobe strongly convex from front to back, laterally compressed and tectiform; scape with sparse and inconspicuous erect setae, about as long as one third maximum width of scape; hind tibia devoid of erect setae or with at most 1 or 2, side of head with 0-5 very short, inconspicuous subdecumbent to suberect setae, posterior margin of head with sparse, long, erect setae; pronotum with posterior row of erect setae; mesoscutum, scutellum and propodeum with moderately abundant erect setae; petiolar node in profile with rim of whitish erect pubescence, no erect setae projecting above apex, posteroventral lobe with abundant setae; gastral terga with sparse erect setae; general body color dark brown, the following lighter yellow brown: thin strip of anterior clypeus and area near mandibular insertions, thin anterior and posterior bands on gastral terga, gastral sterna.
Worker
Measurements (n=9): HLA 1.46 (0.90-1.74), HW 1.38 (0.94-1.69), SL 0.80 (0.61-0.92), CI 95 (94-104), SI 58 (53-68).
Palpal formula 5,3; middle and hind tibia with prominent pectinate apical spur; dorsal surface of mandible with abundant small piligerous puncta, setae in puncta conspicuous, erect, mandible appearing bristly, surface between puncta microareolate, dull; medial and lateral clypeal lobes at about same level; head subquadrate with weakly convex sides, moderately excavate posterior margin; in lateral profile pronotum shallowly convex, mesonotum strongly convex and forming separate convexity that strongly protrudes above level of pronotum; scape with sparse, inconspicuous erect setae, length of setae about one half maximum width of scape; hind tibia lacking erect setae; side of head with 1-2 short erect setae near mandibular insertion, absent elsewhere; posterior margin of head with sparse erect setae; pronotum, mesonotum, and propodeum with abundant erect setae; color red brown.
Similar Species
The bristly mandibles ally this species with A. brevis and A. nigricans. Queens of A. forelii are much larger than either A. brevis or A. nigricans. Workers of A. forelii are superficially similar to workers of A. alfari, but can be differentiated by the setae and dull surface sculpture of the mandibles.
Natural History
Azteca forelii favors tropical dry forest or seasonal wet forest. In Costa Rica it occurs at low density throughout the Pacific slope but is not known from the wet Atlantic slope. It needs large trees in which to nest, and thus mature forests are favored, but large trees along roadsides or pasture edges will suffice.
This species has been collected from ramifying systems of carton galleries on the surfaces of trees. Forel (1899) reported var. xysticola with carton galleries on granitic rocks or on tree trunks. The galleries were reported to be indistinguishable from those of Crematogaster stollii. He later described var. raptrix and concluded that the Azteca had actually invaded and taken over the carton galleries of a Crematogaster stollii nest (Forel 1912).
I have observed colonies of this species three times. One was in Corcovado National Park, Costa Rica, in a canopy Ficus (Moraceae). Fresh carton galleries occurred on nearly every branch and multiple galleries extended down the bole. Another was at Ciudad Neily, also in Costa Rica's southern Pacific lowlands. A similar set of galleries covered the branches of a canopy Sapium (Euphorbiaceae). In this case I discovered that the carton galleries covered the entrances to numerous small cavities in the live branch tips. These cavities were filled with ant brood and coccoid Hemiptera, and occasionally there were alate queens. A third colony was near Santa Marta, Colombia, in Tayrona National Park. A system of carton galleries covered a small roadside Inga (Mimosaceae) tree. A part of the colony occupied the dead core of a live branch. In each case, a few galleries extended all the way down the trunk and into the soil at the base of the tree. No foragers were ever observed outside of the galleries unless the galleries were broken open. Although I found the occasional hemipteran under the surface galleries, I never found ant brood there. All brood and the vast majority of the hemipterans occur in plant cavities to which the galleries lead.
These ants can be difficult to locate in a tropical forest because workers are never exposed on the surface and the galleries are superficially similar to those of the ubiquitous nasutiform termites. However, on close inspection the carton is quite different from termite carton. It is a light-colored coarse thatch instead of the dark mud-like material of termite galleries. The thatch-like galleries are unique in the genus and do not resemble the more papery carton typical of other Azteca (e.g. A. aurita and A. chartifex groups) or the very friable carton of ant garden species. What is remarkable, and this was also observed by Forel, is how similar the carton material and gallery systems are to those of Crematogaster stollii. Crematogaster stollii is broadly sympatric with A. forelii, occurring in about the same densities in the same kinds of habitats. Forel thought that A. forelii might usurp C. stollii nests, and there is also the possibility that C. stollii usurps A. forelii nests, but I have seen no evidence of this. In all the colonies I have seen of both A. forelii and C. stollii, the extensive system of carton galleries was fully occupied and there were areas of fresh carton construction.
Queens were unknown prior to this study. The Ciudad Neily collection is the only one for which workers and queens were associated. A few alate queens have been collected at scattered localities, all of them from blacklights.
Comments
Workers of this infrequently collected species can be recognized by 1) densely punctate/striate mandibles which are opaque nearly to the masticatory margin, and 2) reduced pilosity on the appendages. There are five infraspecific taxa: eiseni (Mexico), championi, raptrix, xysticola (all from Santa Marta area, Colombia), and ursina (Trinidad). The differences among them are minor color differences and I see no evidence of multiple species. I synonymized them all under forelii in Longino (2007).
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
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