Pseudomyrmex elongatus

Typically found nesting in dead twigs of live trees.

Identification
Ward (1989) - P. elongatus is a common and widespread species whose key features are its relatively small size (HW 0.56-0.68); densely punctate and predominantly opaque head; long eyes (REL ≥ 0.53, REL2 ≥ 0.73); and relatively short, high petiole (PU ≥ 0.79). Distinctions between it and Pseudomyrmex caeciliae, Pseudomyrmex cubaensis, and Pseudomyrmex urbanusare discussed under those species.

Distribution
This species occurs from Costa Rica to Texas and in Jamaica, and has been introduced into south Florida (Ward 1985). The Florida populations are isolated from the others. It is common in coastal mangroves, and could have arrived in Florida in floating trees. Moreover, Simberloff and Wilson (1969) showed that this species is likely to be a regular and early colonists of isolated mangrove islets, and must therefore have the habit of flying over open water for hundreds, if not thousands of meters. Pseudomyrmex elongatus could have moved around the Gulf when the climate was warmer. On the other hand, colonies can be found in small dead twigs on live trees and shrubs, and the chance of importation in nursery stock is good. The problem of deciding whether a species is exotic is shown by the two species Pseudomyrmex gracilis (an known introduced species) and Pseudomyrmex elongatus, which currently have similar distributions. If P. gracilis had been introduced into Florida just a few decades earlier, before systematic ant surveys, we probably would have concluded that this species was native to the area. (Deyrup, Davis & Cover, 2000.)

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Belize, Bolivia, Brazil, Colombia, Costa Rica, Cuba, Ecuador, El Salvador, French Guiana, Guatemala, Guyana, Honduras, Mexico, Nicaragua, Panama, Paraguay, Peru, Suriname, Trinidad and Tobago, Venezuela.

It is also found in Paraguay, Ecuador, Brazil, Peru, Venezuela, Suriname, French Guiana, Guyana, Mexico, Guatemala, Honduras, Panama, Costa Rica, Trinidad and Tobago and the United States.

Biology
Ward (1985, 1989) - P. elongatus nests in dead twigs in a variety of woody shrubs and trees. I have collected P. elongatus colonies in twigs of Avicennia germinans, Baccharis halimifolia, Laguncularia racemosa and Rhizophora mangle in Florida, and in Gliricidia sepium, Helicteres, and Inga in Costa Rica and Panama. Among museum material there are records of P. elongatus nesting in a "climbing vine" and "mangrove stems" in Florida, in Quercus virginiana and Prosopis (Texas), and in Quercus fusiformis (Nuevo Leon, Mexico). It has been collected in mangroves, old fields, along roadsides, and in forested habitats ranging from tropical dry forest to secondary and primary rain forest.

Cole (1983) studied the behavior of this ant in red mangroves occurring in southern Florida.

Gillette et al. (2015) in a Chaipas, Mexico field study of twig-nesting ants in coffee plants found C. striatus nesting on plants between 500-1250 m in elevation.

Koch et al. (2018) sampled this species in Caryocar barsiliense trees, in southeastern Brazil cerrado, as part of a study examining species interactions in ant-plants.

Philpot et al. (2018) reported this species was one of the most common ants in an experimental study examining colonization of twigs in shade coffee forests in Chiapas, Mexico (13.3% of the 202 nests found in 796 recovered twigs).

Nomenclature

 *  elongatus. Pseudomyrma elongata Mayr, 1870a: 413 (w.) COLOMBIA. Wheeler, W.M. 1905b: 86 (q.m.); Wheeler, G.C. & Wheeler, J. 1973d: 207 (l.). Combination in Leptalea: Smith, M.R. 1951a: 788; in Pseudomyrmex: Wheeler, G.C. & Wheeler, J. 1956: 384. Senior synonym of tandem: Creighton, 1957b: 18; of alliodorae (and its junior synonym allidora): Ward, 1989: 419. See also: Ward, 1985b: 227; Ward, 1999b: 519.
 * tandem. Pseudomyrma elongata var. tandem Forel, 1906d: 228 (w.) COSTA RICA. Junior synonym of elongatus: Creighton, 1957b: 18.
 * alliodorae. Pseudomyrma alliodorae Wheeler, W.M. 1942: 157, pl. 47, fig. a (w.q.) PANAMA. Wheeler, G.C. & Wheeler, J. 1956: 379 (l.). Combination in Pseudomyrmex: Wheeler, G.C. & Wheeler, J. 1956: 379. Senior synonym of allidora: Brown, 1949a: 42. Junior synonym of elongatus: Ward, 1989: 419.
 * allidora. Pseudomyrma allidora Enzmann, E.V. 1944: 77 (w.) PANAMA. Junior synonym of alliodorae: Brown, 1949a: 42.

Ward (1985): This is the smaller of two elongatus-like species in North America. I am considering it conspecific with P. elongatus Mayr on the basis of (i) the original description of P. elongates, particularly the indication that HL is 1.5 times HW, and (ii) worker material from Costa Rica (leg. Biolley) determined as P. elongatus by Mayr and Forel. There is a confusing variety of elongatus-like forms in Central and South America, which require detailed taxonomic study. Until such a study is carried out, it seems expedient to refer to the North American species as P. elongatus and to leave P. tandem Forel as a provisional synonym.

Pseudomyrmex subater Wheeler & Mann (1914), originally described as a subspecies of P. elongatus, was recognized as a distinct species by Creighton (1955). It may be distinguished from P. elongatus and Pseudomyrmex cubaensis by the shinier integument, conspicuous pilosity (grading insensibly from appressed pubescence to fine suberect and erect setae), broad head (CI 0.83-0.88), short eyes (REL2 0.54-0.58 in P. subater, > 0.62 in P. elongatus and P. cubaensis), distinct petiolar shape (gradually inclined anterior face rounded into a sharply declining posterior fact: so that NI 0.61-0.72), and conspicuous anteroventral tooth on the postpetiole. Apart from two "cotype" workers in the from Haiti, I have seen material of P. subater (misidentifiedd as P. elongatus) from the Bahamas (Andros Island, Nassau) and the same, or a closely related species, from Jamaica (Kingston). Wheeler's (1905) record of "elongatus" from the Bahamas appears to be based on a combination of P. subater and P. cubaensis, judging from material in the MCZ.

Recent collections of P. subater from the Bahamas by Blaine Cole show that this species has striking bright orange queens, which look superficially like those of P. pallidus. Cole also made a collection from a single Cladium culm which contained both 'P. subater' and P. cubaensis workers. These findings suggest that Wheeler's (1905) and Mann's (1920) records of dulotic associations between "flavidula" and "elongata" may have been based in part on pure colonies of 'P. subater', or mixed colonies of 'P. subater' and P. cubaensis.

Worker
Ward (1985) - (n = 24, except for HL, HW, CI, REL, REL2, and PLI, where n = 50): HL 0.78-0.91, HW 0.56-0.64, MFC 0.013-0.024, CI 0.68-0.74, OI 0.52-0.58, REL 0.50-0.58, REL2 0.73-0.82. OOI 0.13-0.48, VI 0.82-0.90, FCI 0.021-0.041, SI 0.42-0.48, SI2 0.55-0.64, FI 0.45-0.56, PDI 0.95-1.45. MPI 0.036-0.072, NI 0.55-0.63, PLI 0.76-0.91, PWI 0.62-0.74, PPWI 1.09-1.40.

A small, brown species with elongate head and eyes (HW 0.56-0.64, CI 0.68-0.74); frontal carinae subcontiguous; occipital margin flat or slightly concave, in full-face dorsal view; basal and declivitous faces of propodeum well differentiated; petiole short, broad, and rounded (PLI 0.76-0.91); postpetiole wider than long. Head densely punctate and usually more or less opaque; remainder of body finely punctate or coriarious-imbricate, varying from opaque to sublucid. Erect pilosity and fine appressed pubescence present on most parts of body, including mesonotum and propodeum; fourth abdominal tergite with a rather dense mat of appressed pubescence.

Type Material
Ward (1989): I found the type worker of P. elongatus, which had previously eluded discovery (Ward, 1985), during a visit to NHMW. It had been misplaced under Pseudomyrmex elongatulus (Daile Torre), a replacement name for the preoccupied P. elongatus (F. Smith, 1877), which is a markedly different species (see Kempf, 1967).

Syntype worker, S. Fe de Bogota, Colombia (Schaufuss) [Examined]; here designated as LECTOTYPE.

Pseudomyrma elongata var. tandem Forel, 1906:228. Syntype workers, EI Hiquito, near San Mateo, Costa Rica (P. Biolley) [Examined].

Pseudomyrma alliodorae Wheeler, 1942: 157. Syntype workers, queen, Ancon, Canal Zone, Panama (W. M. Wheeler) [Examined]. One syntype worker in MCZC here designated LECTOTYPE.

Pseudomyrma allidora Enzmann, 1945:77. Syntype workers, queen, Ancon, Canal Zone, Panama (W. M. Wheeler) (LACM, MCZC) [Examined].