P. radoszkowskii prefers relatively open, dry habitats and does especially well in places modified by human activity. I collected it from along a hotel seawall on Tobago. On St. Vincent, H. H. Smith (cited by Forel 1893j, who described the accessions as “variety luteola”) found it common in open environments from sea level to the edge of the Soufrière Volcano at about 900 meters. Nests on St. Vincent, Smith noted, are usually in the soil beneath a stone or piece of wood in open ground, less commonly within pieces of rotting wood or in rubbish. When beneath an object, the nest is composed of a vertical chamber 8–12 mm wide that branches downward a half dozen cm or so and ends in small chambers 2–3 cm wide. Colonies grow to contain two or three thousand workers, about one-fifth of which are majors. There is apparently only a single fertile queen. In Costa Rica, Longino (1997) found “variety luteola” in similar habitats to those reported by Smith on St. Vincent, nesting beneath dead wood on the ground. Workers forage during the day over the ground and on low vegetation. On Tobago I found they could be recruited in large numbers with baits. Studying the species in Costa Rica, Roberts and Heithaus (1986) observed workers collecting seeds and thus helping to spread the seed shadow of Ficus hondurensis; the ants removed the seeds either directly from fallen fruit or from the feces of frugivorous lizards, birds, and mammals. Winged queens and males of radoszkowskii were found in the Cumberland Valley of St. Vincent in mid-October. (Wilson 2003)
See the description in the nomenclature section.
As presently conceived as one species, radoszkowskii ranges very widely through the New World tropics, from Jamaica, parts of the Lesser Antilles, and Central America south to Bolivia and to Argentina as far as Tucumán. It may prove to be a complex of sibling species, as noted in the Diagnosis (see description below). (Wilson 2003)
Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Bolivia, Brazil, Colombia, Costa Rica, French Guiana (type locality), Greater Antilles, Guatemala, Guyana, Honduras, Jamaica, Lesser Antilles, Mexico, Nicaragua, Panama, Paraguay, Peru, Suriname, Venezuela.
Distribution based on AntMaps
Distribution based on AntWeb specimens
Check data from AntWeb
The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.
- radoszkowskii. Pheidole radoszkowskii Mayr, 1884: 35 (s.w.) FRENCH GUIANA. Senior synonym of acuta, australis, luteola, opacissima, paranana, parvinoda: Wilson, 2003: 221; of medialis: Longino, 2009: 70.
- australis. Pheidole radowszkowskii r. australis Emery, 1890b: 50 (footnote) (s.w.) BRAZIL. Raised to species: Dalla Torre, 1893: 88. Subspecies of radoszkowskii: Emery, 1922e: 99. Junior synonym of radoszkowskii: Wilson, 2003: 221.
- luteola. Pheidole radoszkowskii var. luteola Forel, 1893g: 406 (s.w.q.m.) ANTILLES. Junior synonym of radoszkowskii: Wilson, 2003: 221.
- acuta. Pheidole radowszkowskii var. acuta Emery, 1894c: 154 (s.w.) BOLIVIA. Subspecies of radoszkowskii: Forel, 1909a: 258; Wheeler, W.M. 1925a: 21. Junior synonym of radoszkowskii: Wilson, 2003: 221.
- opacissima. Pheidole radoszkowskii var. opacissima Forel, 1901e: 364 (s.w.) JAMAICA. Junior synonym of radoszkowskii: Wilson, 2003: 221.
- parvinoda. Pheidole radoszkowskii r. parvinoda Forel, 1912f: 223 (s.w.) BRAZIL. Junior synonym of radoszkowskii: Wilson, 2003: 221.
- paranana. Pheidole triconstricta var. paranana Santschi, 1925b: 13 (s.) BRAZIL. Junior synonym of radoszkowskii: Wilson, 2003: 221.
- medialis. Pheidole medialis Wilson, 2003: 208, figs. (s.w.) COSTA RICA. Junior synonym of radoszkowskii: Longino, 2009: 70.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
From Wilson (2003): A widespread abundant species of the diligens group characterized by the following combination of traits.
Major: reddish brown; pilosity sparse, entirely absent from mesosoma; patches of rugoreticulum present mesad to the eyes and anterior half of the pronotal dorsum; longitudinal carinulae cover the frontal lobes and extend most of the way posteriorly to the occiput; all of head, mesosoma, and waist foveolate and opaque; part of first gastral tergite shagreened and opaque; promesonotal profile 3-lobed in dorsal-oblique view.
Minor: reddish brown; carinulae absent or nearly so from body, including dorsum of head; all of head, mesosoma, and waist foveolate and opaque; part of first gastral tergite shagreened and opaque, remainder of gaster smooth and shiny.
P. radoszkowskii as conceived by me is highly variable, and may contain sibling species in addition to named infraspecific forms. (I have split off var. inversa and subsp. pugnax.) The synonymy I propose must therefore be considered provisional. In particular, there is wide variation among nest series in body color, from light to dark reddish brown. The form of the inner pair of hypostomal teeth ranges from long spikes to small denticles that do not reach beyond the hypostomal border; this variation may be bimodal. The amount of shagreening and hence degree of opacity differs from place to place and colony to colony. The extent of the rugoreticular patches also varies considerably. There is, finally, substantial variation in the thickness of the propodeal spine and petiolar node; for example, in the types of “variety acuta” these parts are noticeably thinner, and in “race australis” they are thicker. Only studies of geographicaland local variation will resolve the question of the nature of this variation and the possible existence of a sibling-species complex. Meanwhile, I have chosen the conservative measure of recognizing a single, widespread species. Otherwise, radoszkowskii can be separated from the three species it most resembles, Pheidole diligens, Pheidole inversa and Pheidole pugnax by the following combination of traits in the major: occiput foveolate and opaque; rugoreticulum present mesad to each eye; dorsum of promesonotum devoid of all pilosity; pronotum carinulate or rugoreticulate; anterior third to two-thirds of median strip of first gastral tergite shagreened; color usually reddish brown; 4 teeth present on hypostoma.
MEASUREMENTS (mm) Lectotype major: HW 1.08 HL 1.08, SL 0.72, EL 0.20, PW 0.54. Paralectotype minor: HW 0.54, HL 0.60, SL 0.66, EL 0.14, PW 0.34.
COLOR Major: body and mandibles medium reddish brown, antennae and legs brownish yellow.
Minor: body very dark, almost blackish brown, with a slight tinge of red; appendages medium brown. Other series placed in this species range from light to dark reddish brown.
Figure. Upper: lectotype, major. Lower: paralectotype, minor. Scale bars = 1 mm.
From Wilson (2003): FRENCH GUIANA: Cayenne, collected by M. Jelski. Naturhistorisches Museum Wien, Vienna - as reported in Wilson (2003)
Named after O. Radoszkowsky, author of a list of the ants of Cayenne, French Guiana. (Wilson 2003)
- Forel, A. 1893j. Formicides de l’Antille St. Vincent, récoltés par Mons. H. H. Smith. Trans. Entomol. Soc. Lond. 1893: 333–418.
- Longino, J.T. 2009. Additions to the taxonomy of New World Pheidole. Zootaxa 2181: 1-90. PDF
- Mayr, G. 1884. [Untitled. Descriptions of eight new species.]. Pp. 31-38 in: Radoszkowsky, O. Fourmis de Cayenne Française. Tr. Rus. Entomol. Obshch. 18:30-39. (page 35, soldier, worker described)
- Roberts, J. T. and E. R. Heithaus. 1986. Ants rearrange the vertebrate-generated seed shadow of a Neotropical fig tree. Ecology 67(4): 1046–1051.
- Wilson, E. O. 2003. Pheidole in the New World: A dominant, hyperdiverse ant genus. Harvard University Press, Cambridge, MA. (page 221, Senior synonym of australis, luteola, acuta, opacissima, parvinoda, reflexans)