Dolichoderinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Additional images:
Queen, head, lateral view (small, large), mandible (small, large).
Worker, mandible (small, large).
Range
Costa Rica to Amazonian Brazil and Bolivia. Costa Rica: widespread.
Identification
Queen
Measurements (n=11): HLA 1.60 (1.52-1.65), HW 1.34 (1.27-1.37), SL 0.81 (0.79-0.84), CI 83 (82-85), SI 51 (49-53).
Similar to A. alfari in almost all respects; differing as follows: fourth abdominal tergum with > 10 erect setae (rarely fewer), exclusive of posterior row (< 6 in A. alfari); dorsal surface of head, when viewed in profile, often with setae bridging the gap between the ocellar region and the upper vertex, and often with setae extending up from the clypeus almost to the ocellar region (these areas devoid of setae in A. alfari); scape relatively long (SI 49-54 versus 45-49 in A. alfari); color usually light red brown, A. alfari usually black.
Worker
Measurements (n=5): HLA 1.16 (0.93-1.31), HW 1.02 (0.87-1.19), SL 0.71 (0.59-0.78), CI 92 (88-94), SI 61 (60-67).
Similar to A. alfari in almost all respects and not always distinguishable. In general A. ovaticeps is more setose, with a "scruffy" appearance on the mesosomal dorsum. There are always > 10 setae on the mesonotum, with median number about 20, and they are of irregular length. In contrast, A. alfari has a cleaner look, with fewer dorsal setae. There are 2-17 setae on the mesonotum, with median number 8, and they are of relatively more even length.
Similar Species
Azteca ovaticeps is distinguished from A. alfari as described above. Workers of A. ovaticeps may also be confused with workers of A. forelii. Mandibles of A. ovaticeps workers are smooth and shiny; mandibles of A. forelii workers are roughened and dull.
Natural History
The taxonomy and biology of A. ovaticeps is reviewed in Longino (1989a, 1991b). See also general treatment of the Cecropia-Azteca association in Costa Rica.
In many parts of the Neotropics there are two locally sympatric forms in the alfari complex, one of which is less setose than the other. Longino (1989a) treated them as two species, with the less setose species being alfari and the more setose species being ovaticeps. The distinction is often clear when members of the alfari complex are locally abundant. For example, in the Atlantic lowlands of Costa Rica, ovaticeps queens have a dense brush of setae on the abdomen, and are conspicuously distinct from alfari in the same area. However, in some areas the distinction is not as clear. In Monteverde, some colonies are identical to standard alfari s.s. from elsewhere in Costa Rica. Other colonies show a range of seta abundances, but are not as densely setose as the Atlantic lowland ovaticeps.
Azteca ovaticeps shares behavioral features and size with alfari, but tends to occur in areas of frequent disturbance which are embedded in primary forest: river margins in Brazil and Peru, new roadcuts or new clearings in otherwise forested areas of Costa Rica and Venezuela (Longino 1989a, Yu and Davidson 1997). In Costa Rica, ovaticeps will inhabit any of the myrmecophytic Cecropia species (Longino 1989a, 1991b). At low elevations on the Atlantic slope, most mature trees of Cecropia insignis are inhabited by ovaticeps.
Mature colonies have a dispersed colony structure (Longino 1991a). There is no central carton nest. Brood and any alate sexuals are in branch tips. Older parts of the tree are gradually abandoned, and internal passages are not maintained among occupied branches. Workers are relatively timid and will not defend a mature tree (small saplings are more aggressively defended). When a tree is disturbed, workers usually remain in the branches. Only when a branch is broken open will workers rush out to attack. The foliage of trees occupied by ovaticeps hosts a diverse insect fauna, including foraging ants of other species.
The alfari group, containing alfari and ovaticeps, is a lineage that has colonized Cecropia trees independently of other obligate Cecropia ants (Ayala et al. 1996). Azteca ovaticeps is more geographically variable than A. alfari and may be paraphyletic with respect to A. alfari (Longino 1989a, Ayala et al. 1996).
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
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