Dolichoderinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Additional images:
Holotype queen, face and lateral views (above images), tibia (small, large).
Non-holotype queen, mandible (small, large), petiole, lateral view (small, large).
Worker from type series of A. sericeasur: face and lateral views (above images).
Worker: mandible (small, large), petiole, lateral view (small, large), tibia (small, large).
Range
Guatemala, Costa Rica, Panama. Costa Rica: widespread.
Identification
Queen
Measurements of holotype: HLA 2.14, HW 2.13, SL 1.335, EL 0.518, OC 0.102, MTSC 30.
Measurements (n=10): HLA 2.00 (1.94-2.14), HW 2.00 (1.94-2.17), SL 1.31 (1.28-1.39), CI 100 (99-104), SI 66 (62-67).
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 broadly cordate with rounded sides; 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 to one half maximum width of tibia (MTSC 20-30); sides of head without erect setae; 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 with rim of dense erect whitish pubescence, sparse longer setae, one pair extending above apex in profile, posterior border of sternal lobe of petiole with dense layer of long erect pubescence and several erect setae that are about twice as long as pubescence; 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=9): HLA 1.32 (1.10-1.69), HW 1.31 (1.08-1.76), SL 1.09 (0.99-1.26), CI 99 (96-104), SI 83 (75-90).
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; sides of head without erect setae; posterior margin of head with erect setae; pronotum and mesonotum with abundant long erect setae, somewhat sparser erect setae on dorsal face of propodeum; color light to dark brown, if somewhat bicolored gaster is darker then mesosoma.
Similar Species
The shape and size of the queen head distinguishes this species from all others except A. sericea (a Mexican species). It differs from A. sericea in the presence of erect setae on the posterior margin of the head. It is very similar to A. velox, differing only in the larger size. Azteca gnava and A. instabilis are similar but larger. Azteca gnava has the head solid dark brown; A. sericeasur has much of the anterior and lateral head light orange brown. Azteca instabilis has large ocelli (OCW > 0.20mm); A. sericeasur has small ocelli (OCW about 0.10mm).
Natural History
Azteca sericeasur occurs in moist to wet forest habitats. Queens establish in live stems of understory trees, near the base. Mature colonies are polydomous and dispersed. Foraging columns extend across low vegetation and on the forest floor, connecting multiple small pavilions made of carton (paper-like material constructed by the ants from masticated plant fibers). Clusters of workers and brood occur in the pavilions, and the pavilions may cover membracids and pink scale insects, which the ants tend. Thus the queen is located in a permanent and well-protected site, while the colony is widely spread in a large number of small ephemeral nests.
Along the R’o San Luis near Monteverde, I found workers coming and going from a fissure at the base of a live Xanthoxylem (Rutaceae) at a pasture edge. A colony of Camponotus novogranadensis was using the same entrance, in an apparent case of parabiosis. I have several observations of colonies from the Osa Peninsula. One colony was spread over an area of several square meters, in the dead, hollow core of a live Chimarrhis parviflora (Rubiaceae), in nearby dead sticks, and filling hollow stems of an adjacent Tetrathylacium costaricensis plant (Flacourtiaceae). The Tetrathylacium contained workers, small brood, and mealybugs, but no sexuals or large brood. Small carton nests covered some of the stems and nest entrances. The dead core of the Chimarrhis contained a small pocket of carton, in which I found the grossly distended colony queen and abundant small brood. In another case I found workers streaming through low vegetation. A nest was in a small sapling; the lowest part of the nest was 4m above the ground. There were numerous small cavities and knotholes in the trunk; these were all filled with workers and brood. The lowermost knothole was covered with a carton nest, and the bulk of the workers were in the carton portion. I looked in the carton and in all the knotholes, but I never found a queen. Leanne Tennant, in her study of Tetrathylacium costaricensis in Corcovado, found at least two of her study plants inhabited by A. sericeasur. Males may be produced in large numbers in the small satellite nests. In August, 1982, I observed a series of carton shelters on vine stems at the base of a buttressed tree, and they were packed with hundreds of adult males. Alate queens are few in collections; two were collected in October and one in July. Nest series with alate queens have been taken twice, both in July. I collected a founding queen in the internode of a Cecropia sapling at Estacion Pitilla in the Guanacaste Conservation Area, and Joel Dunn found an incipient colony in a Cordia bicolor plant near Monteverde.
The queens are generally setose ants, with abundant fine flexuous setae on most body parts. An exception was the queen from the Chimarrhis plant described above. This queen was almost completely devoid of erect setae anywhere on the body, including the tibiae, and the pubescence was sparse and patchy. When collecting from this colony, it took me more than an hour to locate the colony center, chop into the Chimarrhis tree, and extract the physogastric queen. This is probably the oldest queen I have examined, the others being alates or foundresses in incipient colonies (and thus more easy to locate and collect). It may be that once queens establish and become sedentary in the middle of a large colony, they gradually become depilated, perhaps through constant grooming by workers.
Comments
This species is very similar to A. sericea, differing in the presence of erect setae on the posterior margin of the head. Azteca sericea is known from Mexico and Guatemala, where it is associated with myrmecophytic orchids.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
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