Azteca flavigaster

Most observations of A. flavigaster have been made in the southern Pacific lowlands of Costa Rica, in moderately seasonal evergreen forest. Azteca flavigaster is a generalist cavity nester with conspicuous surface-foraging workers. In a degraded patch of forest near Quepos, at a pasture edge, I observed abundant workers on the trunk of a live, 40cm diameter tree, emerging from a long narrow fissure at the base. Abundant workers were also on the base of another small tree in the same forest patch. This tree had a dead branch at ground level with workers, brood, and scattered alate females in two parallel cavities, each with horizontal carton partitions. Large columns of workers went up the trunk to a larger dead branch further up. In a patch of mature forest near Ciudad Neily an aggregation of workers were in cavities in the main stem of a sapling of Grias (Lecythidaceae). At Sirena in Corcovado National Park I made several observations of this species. I observed a column of foraging workers on the ground surface, flowing in and out of a 4cm diameter hole extending horizontally into the ground. I observed workers 18m high in the canopy of a Perebea trophophylla (Moraceae) tree, with an aggregation of workers in a small knot. I observed an incipient colony in an ''Acacia alleni'' tree, the common myrmecophytic acacia in Corcovado. The tree was in poor shape, without a dominant Pseudomymex colony. The Azteca occupied several of the thorns, one of which contained a physogastric queen and small brood. Finally, I observed two founding queens in a dead and tattered Costus (Costaceae) inflorescence. The inflorescence was filled with many old chambers containing dead Azteca queen remains. The two living queens were in adjacent chambers, but not in contact. Each had brood, and one had nanitic workers. When I put the queens together in the same vial, they immediately locked mandibles in combat. Other researchers at Sirena have collected founding queens in chambers of Tetrathylacium costaricensis and T. macrophyllum. (Longino 2007)

Identification
Longino (2007) - Among the species with 6,4 palpal formula, A. flavigaster has the smallest queen head size. The most similar species are Azteca quadraticeps, Azteca velox, and Azteca nigra, all of which have larger queen head size. The workers have a unique coloration, with bright yellow gastral dorsum and contrastingly dark brown mesosoma.

Although workers matching A. flavigaster have been found on the Atlantic side of Costa Rica and in other countries, no queens have been collected to confirm these identifications. However, the new species A. quadraticeps is known only from queens from the Atlantic lowlands. It is possible that A. quadraticeps and A. flavigaster are allopatric or parapatric sister taxa with similar workers, and that the Atlantic slope workers with yellow gasters are actually the workers of A. quadraticeps.

Distribution based on Regional Taxon Lists
Neotropical Region: Costa Rica, Ecuador, Mexico, Panama, Peru.

Biology
Longino (2007) - Workers with the same coloration and habitus of Azteca flavigaster occur in the Atlantic lowlands of Costa Rica, but are rare. At La Selva Biological Station these workers have been collected twice. A worker was collected in a Berlese sample of canopy soil and epiphytes, and a nest or nest fragment was found in a live branch of Coussapoa (Cecropiaceae). The nest also contained workers of Camponotus atriceps, in a parabiotic association.

Nomenclature

 *  flavigaster. Azteca flavigaster Longino, 2007: 30, figs. 3, 4A, 5, 6A, 6E, 6F, 8 (w.q.) COSTA RICA.

Worker
(n=4): HLA 1.19 (1.16–1.23), HW 1.20 (1.15–1.26), SL 0.96 (0.94–0.98), CI 101 (99–102), SI 81 (80–82).

Palpal formula 6,4; middle and hind tibia with prominent pectinate apical spur; dorsal surface of mandible smooth and shining, 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 convex sides, strongly cordate posterior margin; in lateral profile promesonotum forming single convexity; 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; side of head with 1–5 erect setae on malar area, otherwise lacking setae; posterior margin of head with abundant erect setae; pronotum, mesonotum, and dorsal face of propodeum with abundant long erect setae; anterior and anterolateral portions of head light yellow brown, variable extent of darker brown on medial vertex and posteriorly, mesosoma variably light to dark brown, gastral dorsum bright yellow, contrasting with darker mesosoma.

Queen
Holotype: HLA 1.62, HLB 1.59, HW 1.53, HW 1.53, SL 1.03, EL 0.44, OC 0.10, MTSC 30.

(n=5): HLA 1.55 (1.54–1.60), HW 1.52 (1.51–1.55), SL 1.04 (1.01–1.04), CI 98 (96–100), SI 67 (65–67).

Palpal formula 6,4; ocelli small; middle and hind tibia with prominent pectinate apical spur; dorsal surface of mandible with small piligerous puncta, setae in puncta short, subdecumbent, interspaces between puncta smooth and shiny on apical half of mandible, gradually becoming faintly microareolate at base; medial and lateral clypeal lobes at about same level; head subquadrate, posterior margin not strongly cordate, very shallowly excavate; petiolar node tall, strongly compressed into thin scale at apex; posteroventral petiolar lobe evenly convex from front to back; scape with abundant erect setae, about as long as one half 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 20–35); sides of head without erect setae; posterior margin of head with erect setae; pronotum with erect setae on posterior margin; mesoscutum, scutellum, and propodeum with abundant erect setae; petiolar node with irregular pubescence and sparse short erect setae, 0–2 pairs of erect setae extending above apex in profile, posterior border of sternal lobe of petiole with uniform layer of short erect setae; gastral terga with sparse long erect setae; most of head dark brown, with lighter orange coloration restricted to anterior malar area near mandibular insertions.

Type Material
Holotype alate queen: Costa Rica, Prov. Puntarenas, Punta Quepos, 9°24'N, 84°10'W, 5m, 4 Jun 1989 (J. Longino) [, specimen (pin) code JTLC000005689].

Paratypes: same data as holotype; 4 workers, 3 alate queens [JTLC000005689, INBC; JTLC000005687, ; JTLC000005688, ; INBIOCRI001281548, ].

Etymology
The name refers to the bright yellow gaster of the worker.

References based on Global Ant Biodiversity Informatics

 * Adams B. J., S. A. Schnitzer, and S. P. Yanoviak. 2019. Connectivity explains local ant community structure in a Neotropical forest canopy: a large-scale experimental approach. Ecology 100(6): e02673.
 * Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
 * Longino J. T. 2007. A taxonomic review of the genus Azteca (Hymenoptera: Formicidae) in Costa Rica and a global revision of the aurita group. Zootaxa 1491: 1-63
 * Longino J. et al. ADMAC project. Accessed on March 24th 2017 at https://sites.google.com/site/admacsite/
 * Longino, J.T. 2010. Personal Communication. Longino Collection Database