Pseudomyrmex pallidus

A common and widespread species that opportunistically nests within a wide range of cavities, from dead stalks of herbaceous plants to dead twigs in trees.

Identification
Ward (1985) - This is the most common and widespread member of the pallidus group. P. pallidus shows considerable geographical variation in size, sculpture, and body proportions (note wide ranges of some metrics). However the workers are consistently orange-brown in color, with contiguous frontal carinae (MFC < 0.025), moderately long eyes (REL2 > 0.52), and (at least weakly) coriarious-punctulate sculpture on the vertex. No other Nearctic species possesses this combination of characters. Specific differences between P. pallidus and other orange Pseudomyrmex (Pseudomyrmex apache, Pseudomyrmex leptosus, Pseudomyrmex seminole and Pseudomyrmex simplex) are discussed under those species.

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Argentina, Belize, Bolivia, Brazil, Colombia, Costa Rica, Cuba, Greater Antilles, Guatemala, Honduras, Mexico, Paraguay, Trinidad and Tobago, Uruguay.

Biology
Ward (1985) - P. pallidus exhibits diversity in its choice of nesting sites. While it shows a preference for dead stalks or culms of herbaceous plants, it will also nest in dead twigs or branches of shrubs and trees in some localities.

By state, the Nearctic nest-site records are from the following plants (based on personal observations or on museum material which I have examined):

Florida: Ambrosia artemisiifolia, Andropogon, Bidens, Cladium jamaicense, Uniola paniculata.

Georgia: Callicarba.

Texas: Baccharis, Heterotheca subaxillaris, Iva ciliata, Melia azedarach, Prunus, Ptelea trifoliata, Uniola paniculata.

Arizona: Gossypium thurberi, Quercus emoryi, Q. oblongifolia.

California: Acacia greggii, Hyptis emoryi.

The number of functional queens in a colony varies widely. The majority of P. pallidus nests which I dissected from Texas and Florida were queenless or monogynous, but sometimes larger numbers of mated, dealate queens cohabited (up to a maximum of 22). Since P. pallidus colonies are often polydomous, the number of queens per colony may be higher.

P. pallidus alates have been collected in every month of the year, indicating that mating occurs in more than one season.

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.

Nomenclature

 *  pallidus. Pseudomyrma pallidus Smith, F. 1855c: 160 (w.) U.S.A. Wheeler, G.C. & Wheeler, J. 1956: 386 (l.); Petralia & Vinson, 1980: 381 (l.). Combination in Leptalea: Smith, M.R. 1951a: 788; in Pseudomyrmex: Wheeler, G.C. & Wheeler, J. 1956: 386. Subspecies of flavidulus: Enzmann, E.V. 1944: 66. Revived status as species: Smith, M.R. 1947f: 544; Creighton, 1950a: 80. See also: Blum & Callahan, 1963: 69; Ward, 1985b: 235.

Worker
Ward (1985) - Measurements (n = 70): HL 0.78-1.06, HW 0.68-0.89, MFC 0.011-0.024, CI 0.77-0.91, OI 0.54-0.62, REL 0.45-0.54, REL2 0.53-0.65, OOI 0.78-2.08, VI 0.67-0.84, FCI 0.015-0.033, SI 0.41-0.49, SI2 0.68-0.85, FI 0.37-0.45, PDI 1.10-1.52, MPI 0.022-0.054, NI 0.54-0.67, PLI 0.47-0.62, PWI 0.38-0.52, PPWI 0.85-1.18.

Diagnosis. - Medium-sized species (for the pallidus group), with moderately broad head (HW 0.68-0.89, CI 0.77-0.91); anterior clypeal margin medially flat, laterally angulate: distance between frontal carinae less than basal width of scape; eyes moderately long. EL greater than scape length: occipital margin convex, flat or weakly concave, in full-face, dorsal view; lateral margins of pronotum rounded; metanotal groove present but shallow; basal face of propodeum longer than declivitous face, and more or less differentiated from it; petiole slender, with a distinct anterior peduncle and anteroventral tooth. Head subopaque to weakly shining; frons densely punctulate on a coriarious background; punctures less dense on the vertex which remains (at least weakly) coriarious; dorsum of mesosoma and petiole sublucid, coriarious-punctulate, becoming coriarious-imbricate laterally; postpetiole and gaster weakly shining, covered with numerous, very fine piligerous punctures. Erect pilosity sparse, lacking on mesonotum, propodeum, and mid and hind femora; one to several erect setae on dorsum of head, pronotum, petiole, postpetiole, and abdominal tergite IV. Fine, appressed pubescence present on most parts of body, forming a moderately dense mat on abdominal tergite IV, which partially obscures the sheen of the integument. Body orange-brown, with paler mandibles and appendages: a pair of anterolateral fuscous patches sometimes present on abdominal tergite IV.

Type Material
Ward (1985) - One syntype queen (dealate), one syntype worker, "U.S.” (Examined). Syntype  worker here designated as LECTOTYPE.