Dolichoderinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Additional images:
Queen, face view (original line drawing) (reduced line drawing), mandible (small, large, original line drawing) (reduced line drawing), petiole, lateral view (small, large).
Syntype worker, Azteca prorsa Wheeler, face view (small, large), lateral view (small, large), mandible (small, large), labels (large).
Range
Costa Rica, Guatemala. Costa Rica: Central and northern cordilleras.
Identification
Queen
Measurements (n=9): HLA 1.47 (1.42-1.55), HW 0.86(0.84-0.91), SL 0.58 (0.56-0.61), CI 59 (57-60), SI 40 (38-41).
Palpal formula 5,3; middle and hind tibia with prominent pectinate apical spur; dorsal surface of mandible with row of large puncta at masticatory margin, these bearing long setae, about 4 large puncta posterior to this row, lacking setae, otherwise puncta small, surface microareolate, dull; medial and lateral clypeal lobes at about same level; head rectangular, posterior margin distinctly excised medially; petiolar node short, bluntly rounded; posteroventral petiolar lobe deep, strongly convex from front to back; scape with moderately abundant erect setae, about as long as one third maximum width of scape; middle and hind tibia with moderately abundant erect setae, longest about as long as one third to one half maximum width of tibia (MTSC 10-20), side of head with 0-4 short, inconspicuous erect setae, posterior margin of head with abundant long erect setae; pronotum with posterior row of erect setae, occasionally a pair of setae on the medial area; mesoscutum, scutellum and propodeum with moderately abundant erect setae; petiolar node in profile with 2-4 pairs erect setae projecting above apex, posteroventral lobe with abundant short erect setae; gastral terga with very sparse erect setae; general body color uniformly dark brown.
Worker
Measurements (n=6): HLA 1.10 (0.94-1.19), HW 0.84 (0.75-0.92), SL 0.54 (0.50-0.58), CI 77 (74-80), SI 50 (49-54).
Palpal formula 5,3; middle and hind tibia with prominent pectinate apical spur; dorsal surface of mandible smooth and shiny on apical half or more, becoming microareolate and dull near base, with sparse puncta, row of puncta along masticatory margin with setae, others lacking setae; medial and lateral clypeal lobes at about same level; head elongate with weakly convex sides, strongly excavate posterior margin; in lateral profile pronotum shallowly convex, mesonotum more strongly convex and forming separate convexity that weakly protrudes above pronotum; scape with moderately abundant erect setae, length of setae about one half maximum width of scape; mid and hind tibia with abundant erect setae, longest about one half maximum width of tibia; side of head with 5-10 short erect setae; posterior margin of head with abundant short erect setae; pronotum, mesonotum, and propodeum with abundant erect setae; color brown.
Similar Species
The 5,3 palpal formula, the presence of tibial spurs, and the elongate rectangular head places A. longiceps among the species treated in Longino (1996). The lack of conspicuous erect setae on the mandibles differentiates it from A. brevis and A. nigricans. The remaining similar species are A. beltii, A. oecocordia, and A. pittieri. Queens of A. longiceps differ from queens of A. beltii in the smaller size and brown color. They differ from A. pittieri in the relatively longer, more rectangular head. They differ from A. oecocordia in the less triangular petiolar node, more setose hind tibia, larger puncta on the mandible, and smaller size.
Natural History
All collections of A. longiceps for which there are biological data are from live stems of Triplaris melaenodendron. Some collections are from mature colonies, and others are founding queens from stump sprouts. Extensive collections in areas where A. longiceps occurs have not revealed it using any other plant species, and so longiceps is presumed to be a host specialist in T. melaenodendron (Longino 1996).
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.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
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