The following account is from Sarnat et al. (2015) and figure numbers refer to that publication.
Pheidole punctatissima is a small species with entirely punctate minor workers that are usually dark red brown to nearly black. The major workers are easily recognizable by the distinct bicolored head which is dark anteriorly and yellowish white posteriorly. Pheidole punctatissima is a member of the Neotropical P. punctatissima clade, together with P. anastasii and P. bilimeki (Economo et al. 2015). Among species treated here, it is easily confused with the aforementioned and with members of the P. flavens complex. Minor workers can also be confused with those of P. parva. Within the P. punctatissima clade, the major workers of P. punctatissima are immediately distinguished from those of both P. anastasii and P. bilimeki by their bicolored heads (Fig. 33). The minor workers of P. punctatissima tend to have relatively narrower posterior head margins and longer antennal scapes than those of P. anastasii and P. bilimeki, but separation can be difficult. See section under P. anastasii for identification notes.
Pheidole punctatissima is a weedy species that tends to be arboreal and prefers open, disturbed habitat (Longino and Cox 2009). It is most commonly found nesting in dead wood on the ground or in dead tree branches. Wilson (2003) reported winged reproductives were found in nests during April and July. Specimen records retrieved from Antweb.org indicate the species was collected from 10–2500 m elevation (570 m average). Pheidole punctatissima has also managed to establish indoors in several European countries. Colonies were found in Denmark infesting a hospital and in Norway inhabiting private homes and a nursing home (Birkemoe and Aak 2008). Birkemoe and Aak (2008)speculated that the species was inadvertently imported along with nursery plants.
Pheidole punctatissima is considered a nuisance pest that can infest structures both in its native and introduced ranges (Longino and Cox 2009). The presence of this species in hospitals and nursing homes suggest it could be a potential nuisance.
Diagnosis of worker among Antkey species. Worker castes bimorphic. Head shape ovoid (minor workers) or subrectangular with posterolateral lobes (majors), but never triangular. Antenna 12-segmented. Antennal club 3-segmented. Antennal insertions at least partly covered by frontal lobes; not surrounded by a raised sharp-edged ridge. Frontal lobes do not obscure face outline between mandible and eye; relatively close together so that the posteromedian portion of the clypeus, where it projects between the frontal lobes, is at most only slightly broader than one of the lobes. Posterolateral corners of head unarmed, without spines. Mandibles triangular. Mesosoma with erect hairs. Pronotal spines absent. Propodeum armed with spines or teeth. Slope of mesosoma steep. Waist 2-segmented. Petiole pedunculate with a distinct and upright node; lacking large subpetiolar process. Postpetiole attached to lower surface of gaster; not swollen; in dorsal view not distinctly broader than long or distinctly wider than petiole. Minor worker characters. Antennal scapes extend beyond posterior margin of head. Antennal scrobe lacking. Postpetiole not swollen relative to petiole. Hairs on mesosoma stout and stiff, arranged in pairs. Head punctate; posterior head margin relatively narrow and rounded. Color brown or reddish brown to black. Scape index (SI) = 114–125. Major worker characters. Antennal scapes do not extend beyond posterior margin of head. Posterolateral lobes distinctly punctate and lacking rugae. Head reddish brown or more rarely yellowish, but never bicolored with the yellowish posterior two-thirds contrasting with the darker brown anterior third and rest of body.
Diagnosis among introduced Pheidole. Body reddish brown to nearly black. Major | HW 0.86–1.06, HL 0.94–1.13, SL 0.56–0.63, CI 92–97, SI 57–68 (n=9, Longino pers. comm.). Head bicolored with the yellowish posterior two-thirds contrasting with the darker brown anterior third and rest of body (Fig. 34). Head subquadrate (Fig. 7); often entirely foveolate (Fig. 11), but portions of posterolateral lobes can be glossy. Posterolateral lobes never with distinct rugae. Promesonotum in profile forming a single dome (Fig. 4), lacking a distinct mound or prominence on the posterior slope. Promesonotal dorsum usually foveolate and never with distinct transverse striae. Postpetiole not swollen relative to petiole (Fig. 3). Postpetiole relatively broad; distinctly more than 2x petiolar width in dorsal view (Fig. 31). Gaster with at least anterior 1/3 of first tergite matte (Fig. 33). Minor | HW 0.44–0.50, HL 0.54–0.59. SL 0.55–0.58, CI 79–85, SI 114–125 (n=14, Longino pers. comm.). Head, including the area mesad of the frontal carinae, entirely covered by reticulated network of punctures (Fig. 37). Posterior head margin relatively narrow (Fig. 58). Antennal scapes lack standing hairs (Fig. 55); scapes surpass posterior head margin by a distance equal to or greater than eye (Fig. 40); scapes relatively long (SI 103–125). Promesonotum in profile forming a single dome (Fig. 42), lacking a distinct mound or prominence on the posterior slope. Hairs on mesosoma stout, stiff, of equal length and arranged in pairs (Fig. 53). Postpetiole not swollen relative to petiole (Fig. 3). Postpetiole broad in dorsal view, distinctly broader than petiole (Fig. 62). Gaster with at least anterior 1/3 of first tergite matte (Fig. 33).
Pheidole bilimeki, Pheidole anastasii
Pheidole punctatissima is considered here as broadly native to the Neotropics from southern Mexico to northern South America. We tentatively treat the Caribbean records as native but these might represent more recent human-mediated dispersal events. The records from southern Brazil, reported at least in part from 10 different urban centers (Lutinski et al. 2013), have not been verified with specimen examination. Should the records refer to P. punctatissima Mayr and not one of its many morphologically similar congeners we would consider this to be an introduced population. Indoor colonies were found in Denmark and Norway (Birkemoe and Aak 2008).