Dolichoderinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Additional images:
Queen, face view (original line drawing, reduced line drawing), lateral view (original line drawing, reduced line drawing), mandible (small, large), petiole, lateral view (small, large), petiole, posterior view (small, large), tibia (small, large).
Worker, mandible (small, large), petiole, lateral view (small, large), tibia (small, large).
Range
Guatemala south through Central America to north coastal Colombia, Venezuela, and Guyana. Costa Rica: throughout.
Identification
Queen
Measurements (n=12): HLA 1.75 (1.56-1.79,6), HW 1.61 (1.45-1.73), SL 0.87 (0.79-0.94), CI 94 (91-98,6), SI 51 (49-53,6).
Palpal formula 5,3; middle and hind tibia with prominent pectinate apical spur; dorsal surface of mandible roughened, dull, with sparse small piligerous puncta, setae in puncta short, larger puncta with long setae near masticatory margin; medial and lateral clypeal lobes at about same level (medial lobe not projecting anteriorly); head quadrate, with sides somewhat convex, weakly cordate posteriorly; petiolar node low, triangular, acute, but apex rounded, not sharp; posteroventral petiolar lobe evenly convex, shallow, not strongly developed, ending before posterior margin of sternite, leaving small rim formed by posteriormost portion of sternite; scape with abundant erect setae, about as long as one half to two thirds maximum width of scape; middle and hind tibia with abundant erect setae, longest of these about as long as maximum width of tibia (MTSC 20-35); sides of head with erect setae variably abundant, from nearly absent to moderately abundant; posterior margin of head with abundant very long setae; pronotum with abundant long setae on posterior third; mesoscutum, scutellum, and propodeum with dense brush of abundant setae; petiolar node with variable number of long setae on apex, abundant long setae on posteroventral lobe; all gastral terga with abundant erect setae; color black.
Worker
Measurements (n=10): HLA 1.36 (1.24-1.44,3), HW 1.01 (0.68-1.35), SL 0.76 (0.53-0.89), CI 94 (94-101,3), SI 64 (60-69,3).
Palpal formula 5,3; middle and hind tibia with prominent pectinate apical spur; dorsal surface of mandible faintly roughened, not smooth and shining, with sparse small piligerous puncta, setae in puncta short to long, larger puncta with long setae near masticatory margin; medial and lateral clypeal lobes at about same level, medial lobe at most weakly projecting beyond lateral lobes; head with convex sides, strongly cordate posterior margin; mesosoma in lateral profile with promesonotum forming a broad convexity, promesonotal suture weakly impressed, such that pronotum and mesonotum tend toward being separate convexities, mesonotum more strongly convex than pronotum; metanotal groove broad; petiole in profile with node less massive than sternal lobe, perpendicular distance from tergosternal suture to apex of node less than distance to ventral margin of sternal lobe (in contrast to A. xanthochroa, on which the petiolar node is larger relative to sternal lobe); scape with abundant erect setae, length of setae about one half maximum width of scape; mid and hind tibia with abundant erect setae, longest setae about one half maximum width of tibia; sides of head with abundant short erect setae from mandibular insertions to level of eye, becoming sparse to absent posterior to eye; posterior margin of head with abundant long curved setae; mesosomal dorsum with abundant erect setae, those on pronotum long, on mesonotum shorter, on dorsal face of propodeum very short, grading into pubescence; color brown.
Similar Species
The queens of A. constructor are very distinctive and not easily confused with any other species. Workers of A. constructor and A. xanthochroa are very similar. Large workers of A. constructor retain a chocolate brown color, while large workers of A. xanthochroa become more mottled orange. The petiolar node of A. constructor workers is relatively low, while the posteroventral lobe is relatively deep and strongly convex. Workers of A. xanthochroa are the reverse, with relatively taller node and shallower ventral lobe.
Natural History
The taxonomy and biology of A. constructor are reviewed in Longino (1989b, 1991a, b). See also general treatment of the Cecropia-Azteca association in Costa Rica.
Azteca constructor is an obligate Cecropia ant. It occurs throughout Costa Rica, in a wide variety of habitats and in a variety of Cecropia species. I have found queens in Cecropia saplings from sea level to 1500m. Queens occur abundantly in saplings of C. peltata, C. obtusifolia, and C. insignis, and I have occasionally found queens in saplings of C. angustifolia, a non-myrmecophytic cloud forest species which does not harbor Azteca colonies when mature. In the lowlands, A. constructor colonies are common in mature trees of C. peltata on the Pacific coast and C. obtusifolia on the Atlantic coast. In the Atlantic lowlands, mature C. insignis trees are dominated by A. ovaticeps (D. and D. Clark, pers. com., and pers. obs.). This contrasts with the uplands, where in relatively undisturbed forest C. insignis is the only myrmecophytic Cecropia species. In these upland sites, saplings are filled with queens of A. constructor and A. xanthochroa, which implies that nearby mature trees of C. insignis must harbor reproductive colonies of A. constructor. Thus, hostplant use appears to vary with region and elevation.
Pleometrosis at colony founding is very common, particularly at upland sites, and I have found up to 10 queens in a single internode. Mixed-species associations are common, with queens of A. constructor and A. xanthochroa inhabiting the same internode. Colonies at a stage where there are hundreds of workers and the queen has become physogastric are generally monogynous, but I have twice observed colonies at this stage with two physogastric queens. In both cases, the queens have been close together in the central carton nest of the colony. Multiple physogastric queens in young colonies are apparently common in Monteverde, Costa Rica (D. Perlman, pers. com.). I have dissected two mature colonies of A. constructor, and both were monogynous.
Mature colonies occupy a single carton nest in the bole of the tree. The nest is spindle-shaped and causes a deformation of the trunk. All larvae and alate sexuals are concentrated in this single nest. Branchtips, which all communicate internally with the carton nest, contain only workers and Homoptera. Workers of this species are extremely aggressive, and respond to any disturbance by pouring out of large fissures near the carton nest and blackening the trunk surface.
Alate queens of this species and another common Cecropia ant, A. xanthochroa, are relatively common in Malaise trap samples from the Atlantic slope rainforests of Costa Rica. No other Azteca species are common in Malaise traps, even though they are common in the environment. Even the other common Cecropia ants, A. alfari and A. ovaticeps, are not common in Malaise samples. This implies that there is something distinctive about the behavior of queens of these two species that makes them more susceptible to capture.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
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