Azteca nigra Forel, 2007

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, pp. 1-63 : 38-40

Azteca nigra Forel 1912 new status

Figures 3,4A,5,6A,6E,6F.

Azteca velox race nigra Forel 1912:48. Syntype workers, queen, males: Panama (Christophersen) [ MHNG] (examined).

Queen characters. Measurements (n=4): HLA 1.61 (1.61-1.63), HW 1.71 (1.64-1.73), SL 1.05 (1.02-1.08), CI 105 (102-107), SI 65 (63-67).

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 shiny, becoming faintly microareolate at base; medial and lateral clypeal lobes at about same level; head with convex sides, posterior margin weakly cordate, shallowly excavate; petiolar node tall, strongly compressed into thin scale at apex; posteroventral lobe of petiole deep, with posterior margin forming a separate convexity that extends as far posteriorly as posterior tergal lobe, with a small notch or concavity between the sternal convexity and the tergal lobe (Fig. 1D, 5); scape with moderately 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 25-30); side of head with 2-4 short erect setae near mandibular insertions, bare elsewhere; posterior margin of head with abundant erect setae; pronotum with erect setae on posterior margin; mesoscutum, scutellum, and propodeum with abundant erect setae; petiolar node rimmed with erect pubescence and sparse longer erect setae, 0-2 pairs of erect setae extending above apex in profile, posterior border of sternal lobe of petiole with dense layer of erect setae of irregular lengths; gastral terga with sparse long erect setae; light orange brown coloration on clypeus, malar area, antennal fossa, and side of head, variable extent of infuscation on medial and posterior vertex.

Worker characters. Measurements (n=4): HLA 1.06 (0.96-1.13), HW 1.04 (0.94-1.14), SL 0.93 (0.90- 0.96), CI 100 (96-101), SI 88 (85-94).

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 moderately to weakly convex sides, moderately cordate posterior margin; in lateral profile promesonotum forming single convexity; posteroventral lobe of petiole with small posterior notch, similar to queen, but small and barely discernable; 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 about 5 erect setae on malar area, short erect setae variably present along entire side of head; 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 and gaster brown.

Similar species. Queens of A. velox , A. quadraticeps , and A. flavigaster are all very similar to A. nigra but differ in head size (Fig. 6A) and the lack of a posterior notch on the posteroventral petiolar lobe (Fig. 1E versus1D). Workers of A. flavigaster , A. nigra , and A. velox are all very similar in terms of size and shape (workers of A. quadraticeps are unknown but are expected to be in this group as well). Workers of A. flavigaster are distinguished from A. nigra by the bright yellow gastral dorsum. Workers of A. velox are most similar to A. nigra in terms of general size and coloration. Azteca velox workers tend to have relatively shorter scapes (Fig. 6F). On the largest workers of A. nigra the presence of a small posterior notch on the posteroventral petiolar lobe may distinguish them from both A. flavigaster and A. velox .

Range. Costa Rica, Panama.

Biology. Azteca nigra occurs in lowland wet forest, where it forms ant gardens in the understory. I have observed two colonies, both in the Atlantic lowlands of Costa Rica. One was in Tortuguero National Park and the other at La Selva Biological Station. The Tortuguero collection was a cluster of small ant gardens in low vegetation. One nest was adjacent to a group of rotten sticks, inside of which were males and winged queens. Inside another stick was an aggregation of Camponotus atriceps workers, living parabiotically with the Azteca . The La Selva collection was also a series of small carton nests sprouting a few epiphytes. The nests were scattered on stems and leaves of a cluster of low melastomes. The nests covered coccoid Hemiptera and contained ant brood. A few higher nests on individual melastome leaves contained alate queens. One basal, central nest was built around a 50cm long dead branch. Camponotus atriceps were parabiotic in the central nest and some of the satellite nests. The Camponotus and Azteca occupied separate chambers, but the chambers were connected and the two species moved freely among each other as the nests were being disturbed. In the central nest, which was a combination of carton chambers and chambers in the dead branch, the Azteca were clearly associated with the carton areas. It appeared that the Camponotus were living parabiotically in the nest of the Azteca , with the Azteca being the primary architects and owners of the nests.

Additional material examined. COSTA RICA: Heredia: La Selva Biological Station , 10°26'N, 84°01'W, 50m , 28 Jan 1989 (J. Longino) - alate queens and workers ; 11km ESE La Virgen , 10°21'N, 84°03'W, 300m , 19 Feb and 20 Mar 2004 (D. Brenes) - worker ; Limón: Tortuguero , 10°32'N, 83°31'W, 5m , 1 Jul 1985 (J. Longino) - workers ; same locality, 5 Jul 1985 (J. Longino) - workers, alate queens, males .