Description.

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.