Pseudomyrmex dendroicus

A mutualist with plants in the genus Triplaris. The ants patrol and aggressively defend the plant they nest in from intruders.

Identification
Ward (1999) - Workers and queens of P. dendroicus and Pseudomyrmex triplarinus can be separated from all other Triplaris-inhabiting Pseudomyrmex by the longer legs and tendency towards a broader head. P. dendroicus can be distinguished from P. triplarinus by the worker characters mentioned above and in the key. Queens of the two species are more distinct, those of P. dendroicus being absolutely larger (queen HW 1.72–2.01 and queen HL 1.82–2.12 compared with HW 1.46–1.60 and HL 1.60–1.73 in P. triplarinus) and having the mandible more modified (with a strong basal incision, and more marked deformation of the upper surface of the mandible).

Distribution
Widely distributed in the western Amazon basin.

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil, Ecuador, Peru.

Biology
Ward (1999) - P. dendroicus is a strict Triplaris associate that co-occurs with Pseudomyrmex triplarinus and Pseudomyrmex triplaridis at some localities. The workers prune vegetation around the host tree, leaving a cleared area at the base of the tree (Ule, 1906b). Davidson et al. (1988) present experimental evidence that this behaviour reduces the invasion success of dominant (and generalist, non-mutualistic) neighbouring ants such as Crematogaster. Additional information on the biology of P. dendroicus is contained in papers by Ule (1906b, 1907), Wheeler (1942), Schremmer (1984) and Davidson et al. (1988, 1989). Schremmer’s investigations of P. triplarinus from Villavicencio, Colombia refer to P. dendroicus, while his observations of P. triplarinus from Since, Colombia represent another species, Pseudomyrmex mordax. Most museum specimens of P. dendroicus are labeled as coming from “Triplaris” (unidentified to species) but some collections are associated specifically with Triplaris americana Linnaeus, including those of Brandbyge, Davidson, Toft, Ule and Ward (part).

Nomenclature

 *  dendroicus. Pseudomyrma dendroica Forel, 1904c: 40 (w.m.) BRAZIL. Combination in Pseudomyrmex: Kempf, 1961a: 408. Junior synonym of triplarinus: Kempf, 1961a: 408. Revived from synonymy and senior synonym of emarginata: Ward, 1989: 436. See also: Ward, 1999b: 490.
 * emarginata. Pseudomyrma dendroica var. emarginata Forel, 1904e: 684 (w.q.) BRAZIL. Junior synonym of triplarinus: Kempf, 1961a: 408; of dendroicus: Ward, 1989: 436.

Worker
Ward (1999) - Measurements (n=34). HL 1.09–1.55, HW 1.07–1.51, MFC 0.126–0.196, LHT 0.92–1.36, CI 0.94–1.04, REL 0.40–0.46, REL2 0.41–0.45, FCI 0.11–0.14, SI 0.42–0.48, FLI 1.74–2.24, FI 0.35–0.40, PLI 0.70–0.85, PWI 0.72–0.86, PPWI 1.29–1.76.

Similar to Pseudomyrmex triplarinus (q.v.) except as follows. Posterior margin of head more markedly concave (frontal view). Frontal carinae better separated, on average. Scape tending to be longer in relation to HL. Petiole less expanded posterolaterally. Subpetiolar process generally subrectangular or fin-shaped, and pointing posteroventrally. Punctulate sculpture slightly denser on upper third of head, on average. Standing pilosity longer but less common, MSC 7–53, HTC 1–11, absent from the posterior margin of the head; erect hairs on the petiole and postpetiole tending to be more notably curved. Head (except for mandibles, scapes and frontoclypeal complex) brown to dark brown and nearly always contrasting with the lighter-coloured mesosoma.

Type Material
Ward (1999) - Lectotype worker, Rio Purus, Brazil (A. Goldi) [Examined].

Pseudomyrma dendroica var. emarginata Forel, 1904c:684. Syntype workers, queen, Mavany Jurua, Amazonas, Brazil (Ule) (, MHNG) [Examined].