Dolichoderinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Additional images:
Lectotype worker, face view (small, large), lateral view (small, large), labels (large).
Different worker from type series (MCZ syntype), face view (small, large), lateral view (small, large), labels (large).
Queen, petiole, lateral view (small, large).
Worker, petiole, lateral view (small, large).
Range
Southern Mexico to Costa Rica. Costa Rica: widespread.
Identification
Queen
Measurements (n=5): HLA 2.19 (2.18-2.20), HW 2.37 (2.33-2.47), SL 1.14 (1.11-1.20), CI 108 (107-113), SI 52 (50-55).
Palpal formula 6,4; ocelli small; middle and hind tibia with prominent pectinate apical spur; dorsal surface of mandible with abundant piligerous puncta, setae in puncta a combination of longer erect setae and shorter subdecumbent setae, interspaces between puncta faintly microareolate with varying development of roughened, acicular sculpture; medial and lateral clypeal lobes at about same level; head with convex sides, posterior margin strongly cordate; petiolar node in lateral view varying from triangular to flattened and scale-like at apex; posteroventral lobe of petiole deep, with posterior margin forming a concave or vertical surface, meeting tergum anterior to posterior limit of posterior tergal lobe; 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 one half maximum width of tibia (MTSC 20-40); side of head with 0-1 erect setae near mandibular insertion, lacking elsewhere; posterior margin of head with abundant long erect setae; pronotum with erect setae on anterior margin and posterior margin, leaving bare space medially; mesoscutum, scutellum, and propodeum with abundant erect setae; petiolar node rimmed with erect pubescence and irregular longer erect setae, 2-3 pairs of erect setae usually extending above apex in profile, posterior border of sternal lobe of petiole with dense layer of erect setae of irregular lengths; gastral terga with moderately abundant long erect setae; almost entire body uniform dark red brown, lighter orange brown around antennal fossa.
Worker
Measurements (n=14): HLA 1.24 {1.00-1.44), HW 1.29 (1.01-1.47), SL 0.94 (0.81-1.01), CI 105 (101-109), SI 77 (70-85).
Palpal formula 6,4; middle and hind tibia with prominent pectinate apical spur; dorsal surface of mandible smooth and shining near masticatory margin, grading to microareolate and dull at base, with moderately abundant small piligerous puncta, setae in puncta short, erect, larger puncta with long setae near masticatory margin; medial and lateral clypeal lobes at about same level; head with strongly convex sides, strongly cordate posterior margin; in lateral profile pronotum evenly sloping, slightly convex, mesonotum more strongly convex, forming separate convexity; posteroventral lobe of petiole well developed, deep; scape with abundant erect setae, length of setae about one half to equal to maximum width of scape; mid and hind tibia with abundant erect setae, longest setae about one half to two thirds maximum width of tibia; side of head with 2-5 erect setae irregularly distributed along side; posterior margin of head with abundant long erect setae; pronotum, mesonotum, and dorsal face of propodeum with abundant long setae, those on dorsal face of propodeum sometimes shorter, sparser, less erect than those on pronotum and mesonotum; most of body light to dark brown.
Similar Species
The queens of A. gnava are most similar in size and shape to queens of A. instabilis and A. sericeasur. They differ from A. instabilis by the small ocelli (OCW < 0.15 for A. gnava, > 0.20 for A. instabilis), and from A. sericeasur by the uniformly brown face (with extensive yellow coloration on A. sericeasur). Azteca gnava differs from both species in the deep posteroventral petiolar lobe, with vertical to concave posterior face. Workers of A. gnava are difficult to distinguish from A. velox and A. nigra. They tend to be somewhat larger than both. The ventral petiolar lobe is more strongly developed than A. velox, and the scapes tend to be relatively shorter than A. nigra.
Natural History
Azteca gnava occurs in the canopy of wet to moist forest habitats, where it forms ant gardens. Ant gardens are moderately abundant in Costa Rica, usually in the canopy of wet to moist forest, and often in trees overhanging streams or river margins. Costa Rican ant gardens are formed by a number of species, including Odontomachus panamensis (in parabiotic association with Crematogaster carinata), C. jardinero, C. longispina, Pheidole violacea, Azteca gnava, and A. nigra.
Azteca gnava ant gardens are large and their associated epiphytes usually appear dense and well established (e.g. robust Aechmea (Bromeliaceae) plants, dense mats of Peperomia (Piperaceae), hemiepiphytic Coussapoa). In Corcovado National Park, Costa Rica, A. gnava ant gardens often have abundant growth of Peperomia macrostachya and Aechmea tillandsioides var. kienastii. Colonies usually occur as one or more large central nests and numerous smaller satellite nests, forming an "archipelago" of ant gardens. Larger nests may be over 50cm diameter. Invariably, large populations of coccoid Hemiptera are sheltered beneath the ant gardens, attached to the supporting branch of the host tree and sometimes on the epiphytes on the nest. Ant brood can be found dispersed throughout the gardens.
Queens were unknown prior to this study and they are very rarely encountered. In the one case in which I observed a colony queen, it inhabited the central and largest ant garden. Very occasionally alate queens are taken in Malaise traps. On Barro Colorado Island, Panama, I collected an alate queen flying in the forest at 1700hrs.
Comments
Azteca gnava may be close to or the same as A. ulei, the ants from Ule's classic studies of Amazonian ant gardens (Ule 1901).
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
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