Widespread in the Neotropics from Costa Rica to Argentina, and on many Caribbean islands. Costa Rica: common in northwest (dry forest habitats); also in Coto banana plantation in southwest.
This is a common dry forest species in northwest Costa Rica. Colonies can occur in very open, disturbed areas. For example, they have been observed in the central city park of Liberia, and in banana plantations at Coto. Workers are seed harvesters, and form conspicuous trunk trails to seed sources. They are also generalist foragers and will readily come to baits. Diurnal and nocturnal foraging have been observed. The nests are in bare soil, with conspicuous nest entrances and chaff piles. Workers have a foetid odor when collected. In Santa Rosa National Park, Longino once observed a colony emigration: a thick column of alate queens and brood-carrying workers extended many meters along the edge of a dirt road.
Forel, A., 1893:
[[ worker ]] [[ queen ]] [[ soldier ]] [[ male ]]. (No. 12 a).
[[ queen ]] (encore inedite). L. 7, 3 mill. Caracteres du [[ soldier ]]. Occiput lisse derriere. Mesonotum subopaque, strie en long, avec des points epars. Scutellum assez lisse, avec des points epars. Meta- notum grossierement ride en travers, aussi sur sa face declive, arme de deux epines pointues, un peu plus longues que la largeur de leur base. Abdomen subopaque, tres finement et vaguement reticule. Thorax assez eleve, aussi large et plus grand que la tete. Second n oe ud du pedicule plus de deux fois plus large que long. Ailes manquent.
[[ male ]]. L. 4,7 mill. Mandibules tridentees. Derriere de la tete convexe-arrondi, presque semicirculaire. Epistome et face declive du metanotum rides en travers. Tete avec des rides eparses. Le reste luisant et assez lisse. Face basale du metanotum plus longue que la face declive et munie de deux tubercules allonges. Pilosite dressee abondante, aussi sur les tibias et les scapes. D'un jaune brunatre sale, avec la tete (sauf les mandibules) d'un brun noiratre. Ailes d'un jaune tres pale, avec les nervures et le pterostigma assez pales.
(12). Low, flat land at the southern end of the island, near the sea. The nest is subterranean, with an opening about 1 / 2 in in diameter to the surface. I do not know how extensive the passages are. Only one formicarium observed.
(12 a). Lowlands, Great Head, southern end of island; in a subterranean nest. All the forms were obtained within six inches of the surface. Apparently the colony was a very large one.
Wilson, E. O.:
Pheidole fallax Mayr 1870b: 984. Syn.: Pheidole fallax r. columbica Forel 1886b: xliv, n. syn. ; Pheidole jelskii var. fallacior Forel 1901j: 356, n. syn. ; Pheidole fallax var. britoi Forel 1912g: 221, n. syn. ; Pheidole fallax var. ovalis Forel 1912g: 221, n. syn. Raised to species level in this monograph: infraspecific variants jelskii , obscurithorax , puttemansi .
Etymology L fallax , deceitful, false; allusion unknown.
diagnosis A member of the fallax group, similar to gigas , jelskii , obscurithorax , puttemansi , roushae , tobini , and valens , and especially the very abundant and widespread jelskii , with which it is easily confused.
Major: posterior half of dorsal surface of head primarily carinulate, with rugoreticulum extensive mesad of the eye most of the way to the occiput; pronotum transversely carinulate; anterior fourth to third of central strip of first gastral tergite shagreened; head tapered toward occiput in side view, as shown.
P. fallax differs from P. jelskii as follows and as depicted: in major, petiolar node higher and descending to peduncle by a much more concave curve, and scapes shorter (Scape Length/Head Width 0.50-0.59 as opposed to 0.60-0.70 in jelskii major); and in minor, occiput much broader and nuchal collar thinner than in jelskii .
Measurements (mm) Lectotype major: HW 1.72, HL 1.84, SL 0.90, EL 0.24, PW 0.80. Paralectotype minor: HW 0.60, HL 0.72, SL 0.92, EL 0.18, PW 0.40.
Color Major and minor: body medium reddish brown, with gaster sometimes dark reddish brown.
Range A circum-Caribbean species, which I have verified from the Greater Antilles (Cuba, Jamaica, Puerto Rico), Central America, Colombia, and Venezuela. No certain records exist from the Lesser Antilles, where the closely related jelskii abounds.
Biology Because fallax has a range enclosed by the more abundant jelskii and is so easily confused with it, natural history notes published in the past under the name of either species are generally unreliable.
Figure Upper: major (compared with lectotype); variation in hypostomal teeth shown is with specimens from Puerto Rico (4 teeth) and Cuba (3 teeth). Lower: minor (compared with paralectotype, which shares the long, thin propodeal spine depicted; the very short spine at the top is of a Panama specimen, and the medium-length spine in the middle is of a syntype of the synonymous " var. columbica "). CUBA: Soledad, Las Villas. (Type locality: Cuba.) Scale bars = 1 mm.
Wild, A. L., 2007:
Canindeyú , Pte. Hayes (ALWC).
Literature records: Pte. Hayes, “Paraguay” (s. loc.) (Fowler 1981, Kempf 1972).
Pheidole fallax is a Central American/Caribbean species highly unlikely to be conspecific with southern South American forms; Wilson (2003) gives distribution. Records probably refer to P. jelskii or P. obscurithorax .