Pseudomyrmex elongatulus

This species is widely distributed in eastern Mexico, from Tamaulipas to Chiapas, with outlying populations in Guatemala and Belize. The record from Morelos needs to be conﬁrmed since it lies outside the expected range of this species. It may represent a transient introduction. There are records of P. elongatulus being intercepted at U.S. ports of entry in Texas and California, from shipments originating in Puebla, San Luis Potosí, and Guatemala (see list of material examined in Ward & Branstetter (2022)), indicating that this species has a propensity to be transported by human commerce. A single worker collected recently by Mark Deyrup in a natural setting in south Florida evidently represents an accidental introduction. It is unclear if P. elongatulus is established in that state; a second visit to the site failed to locate additional workers (Deyrup, personal communication). P. elongatulus has been recorded from lowland rainforest, rainforest edge, second-growth rainforest, mixed tropical/temperate mesic forest, shaded coffee, tropical dry forest, and roadside habitats, at elevations ranging from 20 m to 1355 m (mean 417 m; n = 53). Nests are found in dead twigs of various plants. Speciﬁc nest site records include dead stalk of grass, dead twig of liana, and dead twigs/stems of Cecropia, Heliocarpus appendiculatus, Gliricidia sepium, Mimosa, Orchidaceae, woody Asteraceae, and unidentiﬁed woody plants.

Identification
Medium-sized species (HW 0.93–1.06, LHT 0.80–0.97); head only moderately elongate (CI 0.81–0.90) and with rounded posterolateral corners in full-face view (Fig. 10); eyes relatively large (see REL and REL2 values); frontal carinae separated by less than basal scape width; metanotal groove strongly impressed, conspicuous in proﬁle; dorsal face of propodeum ﬂat, rounding into declivitous face, the two subequal in length; petiole slender, elongate-triangular in proﬁle (PLI 0.47–0.53, PL/HL 0.57–0.61, PL/ LHT 0.75–0.80); petiole with slight anterior peduncle, in proﬁle the anterodorsal face ﬂat to convex, ascending gradually to summit in posterior quarter of node, then rounding into steeply descending posterior face; profemur moderately robust (FI 0.43–0.47); hind leg moderately long (LHT/HL 0.74–0.79). Head subopaque to sublucid, densely punctulate-coriarious, the punctures becoming less dense on vertex (separated by their diameters or more). Standing pilosity sparse, absent from propodeum and mesonotum (MSC 2–4). Typically light yellow-brown to orange-brown, with darker brown anterolateral patches on abdominal tergite 4 (ﬁrst gastric tergite) and brown transverse bands on abdominal tergites 5–7 (gastric tergites 2–4); in some samples from Guatemala and Belize head and mesosoma more infuscated, and gaster tending to be more uniformly medium brown. (Ward & Branstetter, 2022)

Distinctive features of this species are the moderately elongate head with rounded posterolateral corners, large eyes (worker REL 0.47–0.53, queen REL 0.44–0.46), conspicuous metanotal groove in the worker (Fig. 10), and slender elongatetriangular petiole (worker PLI 0.44–0.52, queen PLI 0.45–0.51). Pseudomyrmex elongatulus is typically light yellow-brown to orange-brown with darker transverse maculation on the gaster, but some specimens from Guatemala and Belize are darker brown overall. Leaving aside Pseudomyrmex ereptor, the closest relative of P. elongatulus is Pseudomyrmex exoratus (Fig. 1), easily told apart by its much more elongate head (worker CI 0.67–0.69, vs 0.81–0.90 in P. elongatulus). (Ward & Branstetter, 2022)

Distribution based on Regional Taxon Lists
Neotropical Region: Belize, Guatemala, Mexico, United States.

Nomenclature

 * elongata. Pseudomyrma elongata Smith, F. 1877b: 67 (w.) MEXICO. [Junior primary homonym of elongata Mayr, 1870a: 413, below.] Replacement name: elongatula Dalla Torre, 1892: 89.
 *  elongatulus. Pseudomyrma elongatula Dalla Torre, 1892: 89. Replacement name for elongata Smith, above. [Junior primary homonym of elongata Mayr, 1870a: 413, below.] Combination in Pseudomyrmex: Kempf, 1967c: 6. Senior synonym of decipiens: Kempf, 1967c: 6.
 * decipiens. Pseudomyrma decipiens Forel, 1899c: 95, pl. 4, fig. 9 (w.q.) MEXICO. Wheeler, G.C. & Wheeler, J. 1956: 382 (l.). Combination in Pseudomyrmex: Creighton, 1953b: 132. Junior synonym of elongatulus: Kempf, 1967c: 6.

Type Material

 * Pseudomyrma elongata. Syntype worker, Mexico (BMNH) [examined by Ward & Branstetter, 2022].
 * Pseudomyrma decipiens. Syntype workers, queens, Teapa, Mexico (H. H. Smith) (BMNH, MHNG) [examined by Ward & Branstetter, 2022].

References based on Global Ant Biodiversity Informatics

 * Del Toro, I., M. Vazquez, W. Mackay, P. Rojas, and R. Zapata-Mata. "Hormigas (Hymenoptera: Formicidae) de Tabasco: explorando la diversidad de la mirmecofauna en las selvas tropicales de baja altitud." Dugesiana 16, no. 1 (2009): 1-14.
 * Del Toro, I., M. Vázquez, W.P. Mackay, P. Rojas and R. Zapata-Mata. Hormigas (Hymenoptera: Formicidae) de Tabasco: explorando la diversidad de la mirmecofauna en las selvas tropicales de baja altitud. Dugesiana 16(1):1-14.
 * Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
 * Forel A. 1912. Formicides néotropiques. Part IV. 3me sous-famille Myrmicinae Lep. (suite). Mémoires de la Société Entomologique de Belgique. 20: 1-32.
 * Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
 * Vasquez-Bolanos M. 2011. Checklist of the ants (Hymenoptera: Formicidae) from Mexico. Dugesiana 18(1): 95-133.
 * Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133
 * Wheeler W. M. 1925. Neotropical ants in the collections of the Royal Museum of Stockholm. Arkiv för Zoologi 17A(8): 1-55.
 * Wheeler W.M. 1935. Check list of the ants of Oceania. Occasional Papers of the Bernice Pauahi Bishop Museum 11(11):1-56.
 * Wheeler, William Morton. 1911. Additions to the Ant-Fauna of Jamaica. Bulletin American Museum of Natural History. 30:21-29.
 * Wheeler, William Morton. 1934. Ants From The Islands Off The West Coast Of Lower California and Mexico. The Pan-Pacific Entomologist. 10(3):131-144.
 * Wheeler, William Morton. 1934. Some Ants From The Bahama Islands. Psyche. 41(4):230-232.