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) (original line drawing) (reduced line drawing); head, lateral view (original jpeg) (reduced jpeg); mandible (original line drawing) (reduced line drawing); petiole (original jpeg).
Identification
Nests in live stems Triplaris melaenodendron.
Queen: head subrectangular, head length greater than or equal to 1.3 times head width; head width 0.84-0.91mm (n=7); color black; mandible always with row of piligerous puncta along masticatory margin, but large puncta sparse to absent on mandible surface proximal to this row, and with at most four puncta bearing setae; head strongly rectangular, with flat sides and lateral margin of vertex relatively sharp; head length greater than 0.275 + 1.3(head width); petiolar node relatively high, anterior face somewhat concave; propodeum with setae sparse or abundant; mandible with about 5 large puncta proximal to masticatory margin.
Worker: promesonotum with abundant pilosity; head width of largest workers up to 0.92mm (n=5); propodeum with more than 5 conspicuous erect setae; mandibles with or without bristles; head relatively narrow.
Range
Costa Rica (Alajuela, Guacimal River Valley).
Natural History
The species is now known from the type queen, collected in Alajuela before the turn of the century, and seven collections, all from between 700 and 900m elevation in the Guacimal river valley below Monteverde. The type has no biological data. The seven new collections are all from live stems of Triplaris melaenodendron. Some collections are from mature colonies, and others are founding queens from stump sprouts. Extensive collections in the area have not revealed longiceps using any other plant species, and so longiceps is probably a host specialist in T. melaenodendron.
The following observations, derived from field notes, describe the nesting habits of A. longiceps:
5 July 1991, Longino #2956: I climbed a Triplaris tree and cut out 3 small branches that all contained parts of a colony. No workers appeared as I climbed the tree, nor after I cut branches. A few workers emerged from cut branch bases. Only as I began to split stems did large numbers of workers swarm out. Abundant Homoptera were inside stems, and a few males and a few alate queens. There was abundant worker brood throughout.
I examined a 24cm long section in detail. The internodes contained "knollen," discrete mounds of sticky bran-like material filled with nematodes, tiny dipteran larvae, and what appeared to be abundant stylets of Homoptera. (Knollen are also found in nests of Cecropia ants (Mueller 1880-1881, Longino 1991), and are probably common to many or all stem-nesting Azteca.) There were pink coccids in the occupied internodes: 5, 7, 32, 31, 8, 7, 4 coccids in the 7 occupied internodes. There was a single pseudococcid in these 7 internodes. Many of the exit holes were originally large enough to accommodate a queen, but had been reduced to worker size with resinous carton. Some of the internodal septa were perforated, others not. There were perforated partitions made of resinous carton, which formed artificial septa. Some were found in the middle of internodes, others were partially closing chewed-out internodal septa.
There was one unoccupied internode in the middle of the branch, with solid septa on both sides. The sclerenchyma was thicker on the occupied side than the unoccupied side of the septa, as though the sclerenchyma were a secondary response to ant presence. The walls of ant-occupied internodes were black. The walls of unoccupied internodes were covered with flaky red brown material. Inner diameters of occupied internodes were greater than inner diameters of unoccupied internodes, but the sclerenchyma layer was thicker in the former, again suggesting that the sclerenchyma layer was a response to the ants. The ant entrance holes were irregularly scattered, not in any predictable location. The terminal internodes, near the unoccupied apical shoot area, were the most recently entered.
5 July 1991, Longino #2972: I climbed a 4m tall Triplaris tree. It contained a populous colony, and workers emerged onto trunk when I climbed tree. The largest branch segments I examined from this tree were 3cm dia., and still contained hollow internodes with ants. A large basal section contained relatively few workers and scattered pseudococcids, with no coccids. Exit holes were still maintained through 1cm of wood. I dissected 180cm of occupied branch. There were abundant brood, workers, carton partitions, and exit holes, much like #2956. There were scattered alate queens, and at least one male. Unlike #2956, there was no trace of pink coccids, and pseudococcids were widespread and common.
5 July 1991, Longino #2969-s: I cut one branch from a Triplaris tree. The terminal 20-40cm, the leafy part, was unoccupied. Lower in the branch, 2 founding queens of longiceps and beltii occupied adjacent cavities. The cavities of the two queens formerly were continuous through a perforated septum, but a plug of particulate matter separated the two. The plug was asymmetrical, as though built from the beltii side.
Literature Cited
Longino, J. T. 1991. Azteca ants in Cecropia trees: taxonomy, colony structure, and behavior. Pp. 271-288 in C. Huxley and D. Cutler, eds. Ant-Plant Interactions. Oxford University Press, Oxford.
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.
Mueller, F., 1880-1881. Die Imbauba und ihre Beschutzer. Kosmos 8:109-116.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
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