Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Images available: Worker: face view (original jpeg) (reduced jpeg); mesosoma, lateral view (original jpeg) (reduced jpeg). Queen: face view (original jpeg) (reduced jpeg); head, lateral view (original jpeg) (reduced jpeg); mandible (original line drawing) (reduced line drawing); petiole (original line drawing) (reduced line drawing).
Identification
Nests in live stems.
Queen: head subrectangular, head length greater than or equal to 1.3 times head width; head width 1.10-1.15mm (n=9); color black; mandible with even covering of coarse, piligerous puncta; mandible surface appearing bristly; petiolar node low and blunt, ventral lobe deep; scape relatively short.
Worker: promesonotum with abundant pilosity; head width of largest workers up to 1.0mm (n=3); propodeum lacking setae or with at most one or two short erect setae; mandibles bristly; scapes relatively short; mesosomal pilosity relatively long.
This is a member of the Azteca nigricans complex, the queens of which have the mandibles with an even cover of large piligerous puncta, so that the mandibles are bristly. Azteca nigricans s.s. is known only from the type queen from Panama, JTL-001 occurs in the Pacific lowlands of Costa Rica, and JTL-002 occurs in the Atlantic lowlands. The three "species" differ in queen head size and relative scape length. However, samples are available from few localities, and knowledge of geographic variation in these characters is inadequate to confidently establish species boundaries.
Range
Costa Rica (Pacific lowlands).
Natural History
This species is known from a number of nest collections from lowland rainforest in southwestern Costa Rica, and two alate queens in collections: one from Golfito, and one from Cerro el Hacha near Santa Rosa. The nests were collected from live stems of several plant species.
The following observations, derived from field notes, describe the nesting habits of this species:
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 JTL-001 to be one of the most common inhabitants. This ant-plant has pre-formed chambers that split, allowing entrance of ants without excavation.
Literature Cited
Longino, J. T. 1996. Taxonomic characterization of some live-stem inhabiting Azteca (Hymenoptera: Formicidae) in Costa Rica, with special reference to the ants of Cordia (Boraginaceae) and Triplaris (Polygonaceae). Journal of Hymenoptera Research 5:131-156.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
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