Dolichoderinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Additional images:
Queen, face view (small, large), mandibles (small, large), petiole, lateral view (small, large).
Worker, mandible (small, large), petiole, lateral view (small, large), tibia (small, large).
Range
Mexico to Colombia and Venezuela. Costa Rica: widespread.
Identification
Queen
Measurements (n=11): HLA 1.72 (1.66-1.81), HW 1.72 (1.63-1.84), SL 1.06 (1.03-1.14, 10), CI 100 (98-103), SI 63 (60-65).
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 but faintly microareolate at base to weakly roughened near masticatory margin; medial and lateral clypeal lobes at about same level; head with convex sides, 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 third maximum width of tibia (MTSC 15-30); 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 rimmed with erect pubescence and sparse longer erect setae, 1-2 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
Measurements (n=7): HLA 0.98 (0.76-1.26), HW 0.99 (0.77-1.28), SL 0.82 (0.68-1.01), CI 101 (97-102), SI 84 (78-89).
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 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. quadraticeps have a more quadrate head shape and are less narrowed anteriorly (Fig. 6B). Queens of A. nigra have a somewhat shorter head and the ventral petiolar lobe is deeper and ends before the posterior tergal lobe. Queens of A. flavigaster have smaller heads (Fig. 6A).
Natural History
Azteca velox is a common species in a wide variety of habitats. It occurs most abundantly in seasonally dry areas, synanthropic habitats, and beach margins. Workers are common diurnal surface foragers. They are generalized scavengers and frequently visit extrafloral nectaries. The nests are polydomous, dispersed in multiple plant cavities. The cavities can be in live or dead stems. Colonies have also been associated with myrmecophytic orchids: Epidendrum bicornutum in Costa Rica (Forel 1906) and Caularthron bilamellatum in Panama (Fisher 1992). Colonies also develop, to variable extent, carton nests as extensions of nests in plant cavities.
In Santa Rosa National Park, Costa Rica, I observed several colonies. An incipient colony was in the hollow live stems of an understory shrub, Cassia hayesiana (Fabaceae). The total stem length of the occupied space was about 1m, with inner cavity diameter of 0.5-1.0cm. There was one physogastric queen and no other reproductives. At two entrance sites they had built small globular carton dwellings, 2cm across and packed with workers and brood. The section of hollow stem near the queen was entirely plugged with a mass of eggs and young brood. The nest also contained a Microdon (Syrphidae) puparium.
A second incipient colony was in a shaded Cordia alliodora tree, a myrmecophyte usually occupied by Azteca pittieri. A lone physogastric queen was in one of the internodes, and workers and brood were dispersed in other nodes of the tree. Some of the Cordia nodes had small carton nests built on the surface.
In the forest at Santa Rosa I also observed a parabiotic association between Azteca velox and Camponotus atriceps. Workers of Azteca and Camponotus were running in and out of the same fissure in a tree trunk, showing no aggressiveness toward each other.
I observed a colony near Punta Quepos, at the edge of a small patch of degraded forest surrounded by pasture. About 4m of trailside had 10-20cm long carton nests scattered in the vegetation, on larger stems. I scraped one nest into a plastic bag - it contained a very high density of workers but no brood. A dead branch, in contrast, was packed with brood, males, and alate females. The dead branch was 3cm diameter with a 1-1.5cm diameter continuous internal cavity. The ants had constructed rather regular perforated platforms inside the branch, every 1-1.5cm, making the inside look much like a Cecropia branch interior.
Comments
Neither the morphological definition of this species nor the use of the name A. velox are very well supported. The differences among A. sericeasur, A. velox, A. nigra, A. quadraticeps, and A. flavigaster are subtle. I base the differences among the species mainly on the queens. The Azeca velox queen is smaller than A. sericeasur, larger than A. flavigaster, with more rounded head than A. quadraticeps, and longer head than A. nigra. These conclusions are based on very small sample sizes of available queens. Workers of A. flavigaster have a distinctive color pattern (contrasting yellow gaster and brown mesosoma), and the workers of A. quadraticeps are unknown. The workers of A. sericeasur, A. velox, and A. nigra are very similar. The largest workers of A. velox and A. nigra are always relatively small. In the field even large populous colonies are entirely composed of small workers. In contrast, populous colonies of A. sericeasur (and A. instabilis, which is hard to distinguish from this group in the field) have much larger workers in amongst the small workers. Azteca velox and A. nigra workers differ slightly in scape length, with A. velox having proportionately shorter scapes. Azteca nigra appears to be a wet forest version of A. velox, having similar nesting behavior of using a combination of dead sticks and carton nests, but with much greater development of the carton nests into ant gardens.
The types of A. velox are a few small workers from Mexico, collected in the late 1800's. They have erect setae on the posterior margin of the vertex, distinguishing them from A. sericea, the size is small, separating them from A. sericeasur, and the scapes are relatively short, separating them from A. nigra. The fact that the species I am calling A. velox is common in the open, seasonally dry habitats of Santa Rosa National Park, and Santa Rosa has many ant species that are widespread in similar habitats from there to southern Mexico, further strengthens the identity.
Forel (1899) discovered the Pergande homonym fasciata and proposed the replacement name velox. At the same time he described the queen and male, based on additional material from Costa Rica (Tonduz); Panama, Bugaba (Champion); and Colombia, pied de la Sierra Nevada de Santa Marta (Forel). It was not clear from which specimens he described the various castes. He noted that the species lived in hollow trunks, including fallen dead trees, and that it was uncertain whether carton construction was used for the nest. Some of this non-Pergande material has been incorrectly labeled as types and distributed to museums (MCZC, AMNH). The USNM, however, has true syntypes from Pergande's original collection (type #4481), in the type collection.
In the same paper Forel described the subspecies nigriventris, based on his material from the Santa Marta region of Colombia. The syntypes included queens. I examined this material and it matched my concept of A. velox. Forel (1906:241) later identified additional Costa Rican material as nigriventris. This material was collected by Biolley in Esparza, from pseudobulbs of Epidendrum bicornutum, with the note "in constant symbiosis." I examined this material and it matches my concept of A. velox.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
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