Pseudomyrmex triplarinus

P. triplarinus has been collected from Triplaris americana (=T. noli-tangere Weddell), and other Triplaris trees not identified to species. The habits of P. triplarinus appear to be similar to those of Pseudomyrmex dendroicus, i.e. workers readily attack and sting intruders and they clear vegetation from the base of the host tree. An ecological study by Oliveira et al. (1987) in Brazil demonstrated that P. triplarinus workers were more efficient than a co-foraging Crematogaster species at finding and capturing termite baits on host foliage. (Ward 1999)

Identification
Ward (1999) - P. triplarinus may be recognized by the following combination of traits: relatively large species (worker HW > 0.99, LHT > 0.81; queen HW 1.46–1.60, queen LHT 1.19–1.41); head broad (worker CI > 0.91, queen CI 0.90–0.95), covered with fine punctures separated by one to several diameters; head not contrastingly darker than the mesosoma; pilosity abundant on mesosoma dorsum and external face of metatibia (worker MSC > 40, worker HTC > 8) but absent from side of head (frontal view); legs relatively long (worker LHT/HL > 0.76); petiole longer than wide, especially in the queen (worker PWI <1.00, queen PWI 0.75–0.84), and with a subtriangular subpetiolar process which is directed ventrally. The relatively slender legs alone separate P. triplarinus from all other Triplaris inhabitants except Pseudomyrmex dendroicus, from which it differs by the more abundant pilosity, ventrally directed subpetiolar process, and several other features (see P. dendroicus). P. triplarinus shows a moderate amount of variation, especially in body colour. Light-and dark-coloured workers may occur in the same population and within single nest series.

Distribution
Southern Colombia through the Amazon basin to Bolivia and the pantanal of southwestern Brazil.

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

Nomenclature

 *  triplarinus. Myrmica triplarina Weddell, 1850: 263 (footnote) (w.) BRAZIL. Wheeler, G.C. & Wheeler, J. 1990a: 464 (l.). Ward, 1999b: 505 (designation of neotype). Combination in Pseudomyrma: Wheeler, W.M. 1942: 186; in Pseudomyrmex: Wheeler, G.C. & Wheeler, J. 1956: 386. Senior synonym of arborissanctae: Wheeler, W.M. 1942: 186; of ecuadoriana: Brown, 1949a: 44; of cordobensis, rurrenabaquensis: Ward, 1999b: 505. See also: Kempf, 1961a: 408.
 * arborissanctae. Pseudomyrma arborissanctae Emery, 1894c: 147 (w.q.) BOLIVIA. Junior synonym of triplarinus: Wheeler, W.M. 1942: 186.
 * cordobensis. Pseudomyrma arborissanctae var. cordobensis Forel, 1914d: 265 (w.) ARGENTINA. Combination in Pseudomyrmex: Kempf, 1961a: 400. Subspecies of triplarinus: Wheeler, W.M. 1942: 188. Junior synonym of triplarinus: Ward, 1999b: 505.
 * rurrenabaquensis. Pseudomyrma triplarina var. rurrenabaquensis Wheeler, W.M. & Mann, in Wheeler, W.M. 1942: 188 (w.) BOLIVIA. Combination in Pseudomyrmex: Kempf, 1961a: 401. Junior synonym of triplarinus: Ward, 1999b: 505.
 * ecuadoriana. Pseudomyrma arborissanctae var. ecuadoriana Enzmann, E.V. 1944: 79 (w.) ECUADOR. Junior synonym of triplarinus: Brown, 1949a: 44.

Worker
Ward (1999) - Measurements (n=39). HL 1.03–1.46, HW 1.00–1.41, MFC 0.108–0.158, LHT 0.82–1.23, CI 0.92–1.00, REL 0.40–0.45, REL2 0.42–0.47, FCI 0.10–0.14, SI 0.43–0.48, FLI 1.45–2.09, FI 0.34–0.39, PLI 0.76–0.91, PWI 0.78–0.98, PPWI 1.37–1.76.

Relatively large species (HW > 1.00, LHT > 0.80). Basal margin of mandible with mesial tooth located notably closer to the apicobasal tooth than to the proximal tooth (MD4/MD5 approximately 0.75–0.80); masticatory margin of mandible with six or (less commonly) seven teeth. Palp formula 6,4. Median clypeal lobe anterolaterally rounded or bluntly angled (not sharply angulate), its anteromedial surface deflected ventrally. Frontal carinae well separated (MFC > 0.10), subparallel or converging slightly posteriorly (ASM ≈ PFC ≥ MFC). Median lobes of antennal sclerites not conspicuously exposed (PFC/ASD 0.67–0.83; FCI2 0.57–0.79). Scape of moderate length for the species group, expanded distally to twice its basal width; funiculus short, also expanded apically, the terminal segment about 1.5–1.6 times the width of the first segment; funicular segment 2 about as broad as long, funicular segment 3 as broad as long or slightly broader than long (FLI > 1.44); funicular segments 4–10 broader than long. Eye small for the genus, of moderate size for the species group (see REL and REL2 values), only moderately elongate (OI 0.58–0.65). Head rather broad (CI > 0.91), the sides convex and either subparallel or diverging slightly posteriorly; side of head rounding relatively abruptly into the posterior margin, which is flat or very slightly concave, in frontal view. Mesosoma dorsum more or less flattened, but mesonotum may be inclined slightly relative to the dorsal face of the propodeum. Metanotal groove deeply incised (MP 0.039–0.093, MPI 0.037–0.075). Dorsal face of propodeum varying from flat to rather convex, subequal to or somewhat longer than the declivitous face (PDI 0.92–1.28), and meeting the latter at a well rounded angle. Metapleural gland bulla well-developed and conspicuous. Legs relatively long, LHT/HL 0.78–0.93. Petiole slightly longer than high (PLI < 0.92), with a weakly differentiated anterior peduncle, followed by an increasingly convex anterodorsal face which rounds into the steep posterior face (lateral view). Summit of node behind the midpoint of the petiole (NI 0.52–0.64). Anteroventral petiolar process well developed, subtriangular in shape and pointing ventrally not posteroventrally. In dorsal view, the minimum (anterior) width of petiole generally less than or equal to half the maximum width (PW13 0.42–0.53), petiolar spiracles forming prominent lateral bulges, and the straight sides of the petiole notably diverging posteriorly. Postpetiole globular, notably broader than long (PPWI >1.35); ventral protrusion of postpetiolar sternite less prominent than in P. concolor; anteroventral process of postpetiole moderately developed. Mandible typically sublucid, with scattered punctulae and fine striolation; the striolae sufficiently dense in some workers to dull the lustre. Head dorsum with numerous fine punctulae (0.005–0.015mm diameter) on a smooth, shiny background. Punctures more or less evenly spaced and separated by about their diameters or less on anterior portion of head, becoming a little less dense on the upper half of head where they are separated by one to several diameters. Mesosoma dorsum sublucid, with numerous piligerous punctures (separated by one to several diameters), side of mesosoma with punctulae less well defined and with a tendency toward the development of corarious-imbricate and imbricate-costulate sculpture, with a corresponding dulling of the integument, especially on the metapleuron and lateral propodeum. Petiole, postpetiole and gaster sublucid, the reflectance dulled (especially on the gaster) by very fine punctulae and associated appressed pubescence. Standing pilosity common and conspicuous on most of body, including scape, mesosoma dorsum, and external faces of tibiae (MSC 43–84, HTC 9–21); erect setae absent from the side of the head, present or absent on the posterior margin. Appressed pubescence well developed on most of body; appressed hairs mostly short and inconspicuous on head, longer and moderately dense elsewhere, including the petiole, postpetiole and abdominal tergite IV where hairs are separated by much less than their lengths. Body varying in colour from uniformly light yellow-brown or orange-brown to dark-brown; head concolorous with or only slightly darker than the mesosoma; gaster may be constrastingly darker than rest of body. Scape, appendages, and frontoclypeal complex tending to be lighter in colour than rest of body.

Type Material
Ward (1999) - Syntype workers, Brazil, Bolivia, Peru (not located; see below). Neotype worker here designated: Estacion Biologica Beni, 42 km E San Borja, Depto. Beni, Bolivia, 210 m, 14°48’S, 66°23’W, P. S. Ward# 9075.

Pseudomyrma arborissanctae Emery, 1894:147. Syntype workers, queens, Bolivia (Balzan) [Examined].

Pseudomyrma triplarina var. rurrenabaquensis Wheeler & Mann, 1942b:188. Syntype workers, Rurrenabaque, Bolivia (W. M. Mann) (, MCZC) [Examined].

Pseudomyrma arborissanctae var. ecuadorianus Enzmann, 1944:79. Three syntype workers, Ecuador (MCZC).

Weddell (1850) introduced the name Myrmica triplarina in a footnote to a paper containing descriptions of new species of Triplaris and other plants. No type material is known to exist for P. triplarinus and Weddell’s herbarium specimens of Triplaris apparently do not contain ants (J. Brandbyge, pers. comm.). Hence I am designating a neotype which agrees with Weddell’s original (albeit scanty) description of the ant, and which corresponds to the species which has come to be known in the literature as P. triplarinus.