Dolichoderinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Additional images:
Queen, mandible (small, large, original line drawing, reduced line drawing); petiole, lateral view (small, large, original line drawing, reduced line drawing).
Syntype worker, face view (small, large), lateral view (small, large), labels (large).
Range
Costa Rica: southern Pacific lowlands.
Identification
Queen
Measurements (n=9): HLA 1.57 (1.49-1.59), HW 1.11 (1.10-1.16), SL 0.62 (0.60-0.64), CI 74 (72-76), SI 41 (40-42).
Palpal formula 5,3; middle and hind tibia with prominent pectinate apical spur; dorsal surface of mandible coarsely punctate, puncta bearing stiff erect setae, mandible appearing bristly; medial and lateral clypeal lobes at about same level; head subrectangular, posterior margin weakly excised medially; petiolar node short, broadly triangular; posteroventral petiolar lobe strongly convex from front to back, laterally compressed and tectiform; scape with sparse and inconspicuous erect setae, about as long as one third maximum width of scape; hind tibia devoid of erect setae or with at most 1 or 2, side of head with 0-2 short setae near mandibular insertion, setae lacking elsewhere, posterior margin of head with moderately abundant erect setae; pronotum with posterior row of erect setae and occasionally setae on medial area; mesoscutum, scutellum and propodeum with moderately abundant erect setae; petiolar node lacking rim of whitish erect pubescence, in profile with 2 erect setae projecting above apex, posteroventral lobe with abundant long setae; gastral terga with sparse erect setae; general body color dark brown.
Worker
Measurements (n=3): HLA 1.07 (0.99-1.09), HW 0.96 (0.89-1.00), SL 0.51 (0.48-0.51), CI 93 (92-94), SI 49 (48-50).
Palpal formula 5,3; middle and hind tibia with prominent pectinate apical spur; dorsal surface of mandible with abundant piligerous puncta, surface between puncta smooth and shining, variable extent of base faintly microareolate; medial and lateral clypeal lobes at about same level; head subquadrate with weakly convex sides, moderately excavate posterior margin; in lateral profile mesosoma compact, pronotum and mesonotum nearly forming a single convexity, with promesonotal suture very weakly impressed; scape with sparse, inconspicuous erect setae, length of setae about one half maximum width of scape; hind tibia lacking erect setae; side of head lacking erect setae; posterior margin of head with sparse erect setae; pronotum and mesonotum with abundant erect setae, dorsal face of propodeum lacking erect setae; color red brown.
Similar Species
The bristly mandibles ally this species with A. forelii and A. nigricans. Queens of A. brevis are smaller than queens of A. forelii. Queens of A. brevis have shorter scapes than queens of A. nigricans (SI 39-43 versus 50-52, respectively). Workers of A. brevis are distinguished from workers of A. nigricans by the reduced number of setae on the hind tibia, 0-2 on A. brevis versus > 5 on A. nigricans.
Natural History
In Costa Rica A. brevis is known only from the Pacific side, and mostly from the wet forests of the southern Pacific lowlands. Nests are in live stems of trees. Stems occupied by ants are covered with runways of characteristic crusty black carton, with the carton full of small round holes from which workers emerge. Colonies are polydomous, with workers and brood distributed in multiple branch tips. Colonies maintain large populations of coccoid Hemiptera inside the stems. Nests have been found in Licania (Chrysobalanaceae), Grias (Lecythidaceae), Myriocarpa (Urticaceae), Tetrathylacium costaricensis (Flacourtiaceae), Ocotea nicaraguensis (Lauraceae), and an unidentified tree in the Moraceae. Leanne Tennant, studying the incipient ant plant Tetrathylacium costaricensis, found A. brevis to be one of the most common inhabitants.
The following specific observations are from field notes:
28 Aug 1982, Longino #28Aug82/1500: In the uppermost crown area of a large Licania tree (Chrysobalanaceae), a colony occupied chambers in the center of nearly every branch tip I could reach. The chambers looked chewed out by ants, and were not a natural feature of the plant. The chambers had many pink coccids on the walls, and some chambers had brood. The branches showed a history of synchronous new growth flushes. Chambers in the latest flush were most active; chambers in older or dead stems were abandoned or had few workers. The chambers in sequential shoots were usually not connected. All the chambers were connected externally by an extensive system of galleries, made of a black, very crusty carton, filled with tiny, circular holes.
3 Sep 1982, Longino #3Sep82/1100: In the same canopy Licania, I observed a queen investigating a small hole in a living shoot. The hole was too small for her to enter.
25 Mar 1990, Longino #2651: A colony occurred in live stems of a small Grias tree (Lecythidaceae). Branch surfaces were covered with black, crusty carton, with a high density of small, circular entrance holes. Irregular cavities in stems contained abundant Homoptera.
28 Sep 1982 (Longino): Founding queens were in separate chambers at the tips of living branches, 10m high in a tree (Moraceae). The stems of this tree frequently had small, pre-formed internal chambers, some with dead Azteca remains.
Leeanne Tennant studied the ant-plant Tetrathylacium costaricensis (Flacourtiaceae) in Corcovado National Park, during July 1987. She found A. brevis to be one of the most common inhabitants. This ant-plant has pre-formed chambers that split, allowing entrance of ants without excavation.
Comments
This species was discussed in Longino (1996) as an unnamed morphospecies (JTL-001) similar to A. nigricans. Examination of the types of A. brevis revealed that it was conspecific with this morphospecies.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
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