Pogonomyrmex theresiae

Robert A. Johnson, 2015, A taxonomic revision of South American species of the seed-harvester ant genus Pogonomyrmex (Hymenoptera: Formicidae). Part I, Zootaxa 4029 (1), pp. 1-142 : 132-134

Pogonomyrmex theresiae

( Figure 68)

Pogonomyrmex theresiae Forel, 1899 b: 303 (worker). Holotype worker [ZSM, CASENT0281108], ECUADOR, Guayas: Estero Salado near Guayaquil; Forel, 1899c: 274 (worker redescribed as new).

Worker. Diagnosis. The combination of: (1) first gastral tergum lacking striae, (2) superior propodeal spines consisting of small tubercles or denticles, and (3) transverse rugae on dorsum of postpetiole uniquely characterize this species ( Figure 68).

Measurements —holotype. HL 1.45; HW 1.46; MOD 0.30; OMD 0.39; SL (scapes missing); PNW 1.01; HFL 1.42; ML 1.67; PW 0.36; PPW 0.52. Indices: SI (scapes missing); CI 100.69; OI 20.55; HFI 97.26.

Redescription. Head quadrate (CI = 100.69), widest just posterior to eye; posterior margin weakly convex in full-face view. Longitudinal rugae on cephalic dorsum prominent, weakly wavy; in full-face view, medial rugae diverging weakly toward posterior corners of head. In profile, cephalic rugae converging approximately midway between posterior margin of eye and vertex. Cephalic interrugae moderately granulate, weakly shining; vertex weakly to moderately rugose, interrugae smooth, strongly shining. Anterior margin of clypeus concave; dorsal surface with numerous subparallel, longitudinal rugae. Mandibles with six teeth; mandibular dorsum coarsely rugose. Numerous moderately long, curved, bristle-like, cream to light yellowish hairs project from basolateral margin of mandibles. MOD = 0.21x HL. In profile, eyes situated near middle of head, OMD = 1.30x MOD. Scapes missing; scapes not reaching vertex as per Forel (1899c). Psammophore well-developed.

Mesosomal profile moderately convex; all mesosomal surfaces with prominent rugae. In profile and dorsal views, humeral shoulders of pronotum enlarged, angulate. Dorsum of promesonotum and sides of pronotum rugoreticulate to vermiculate. Mesopleura with irregular rugae angling posterodorsally. Dorsum of propodeum with irregular rugae to rugoreticulate. Superior propodeal spines consist of small denticles or tubercles; inferior propodeal spines weakly developed, consisting of a small, broadly rounded, triangular process. Propodeal spiracles narrowly ovate facing posterad. Interrugae on mesosoma moderately granulate, dull to weakly shining. Legs weakly coriarious, weakly shining to smooth and shining.

Peduncle of petiole about as long as petiolar node, anteroventral margin with bluntly rounded triangular process. In profile, posterior surface of petiolar node weakly convex; petiolar node asymmetrical with anterior surface slightly shorter than posterior surface, apex weakly rounded to subangulate. In dorsal view, petiolar node longer than wide, narrowest at posterior margin, gradually widening to spatulate anterior margin; posterior surface with moderately strong, wavy to irregular transverse, sometimes discontinuous rugae. Dorsum of postpetiole convex in profile; in dorsal view, widest near posterior margin, narrowing to anterior margin; maximal width about equal to length; dorsum and sides with wavy transverse rugae that are finer, denser, more regular than those on posterior surface of petiolar node. Interrugae on posterior surface of petiolar node and dorsum of postpetiole weakly granulate, weakly shining to smooth and shining. Base of first gastral tergum weakly coriarious, shining, remainder smooth, strongly shining.

Short, erect, whitish pilosity sparse on head. Scapes missing; as per Forel (1899c) scapes with a few scattered oblique, short, stiff, yellowish hairs. Mesosoma, petiolar node, postpetiole, and gastral terga mostly lacking hairs except for several short, suberect hairs on legs, mesopleura, posterior declivity of propodeum, and ventral surface of postpetiole. Head ferruginous orange; mesosoma slightly darker ferruginous orange; petiolar node, postpetiole, gaster, and legs blackish-orange ( Figure 68).

Queen. Unknown .

Male. Unknown .

Additional material examined. None.

Etymology. Forel dedicated this interesting species to her Royal Highness Princess Therese of Bavaria, who collected this ant.

Discussion. Pogonomyrmex striatinodis is the only congener known to occur in Ecuador, but it is only known from mesic forests, lacks a psammophore, and has long superior and inferior propodeal spines. Alternatively, P. theresiae has a well-developed psammophore and lacks superior and inferior propodeal spines. Pogonomyrmex naegelii might also occur in Ecuador; P. theresiae is easily distinguished by transverse rugae on the posterior surface of the petiolar node and dorsum of the postpetiole (rugoreticulate in P. naegelii ) and absence of superior propodeal spines (present in P. naegelii ).

Forel described P. theresiae twice in the same year. The original description (Forel, 1899b) indicated that the type locality was Colombia, while the redescription gave the type locality as Estero Salado, near Guayaquil, Ecuador. The label on the holotype gives the locale as Estero Salado, verifying that the correct type locality was given in the redescription (Forel, 1899c).

Biology. Nothing is known about the biology of P. theresiae , which appears to be known from only one worker that was collected over 100 years ago at Estero Salado near Guayaquil, Ecuador, in the Western Ecuador Moist Forests ecoregion as defined by Olson et al. (2001) ( Figure 69). Guayaquil is currently the largest and most populous city in Ecuador, such that the type locality is probably urbanized or destroyed. However, it might be productive to search for P. theresiae along roadsides in agricultural areas surrounding Guayaquil, as many North and South American congeners commonly occur in disturbed habitats. Other areas in which to search for P. theresiae would seem to be those that have a tropical savanna climate similar to that of Guayaquil, including western portions of Guayas and Manabí Provinces and the southernmost part of Esmeraldas Province (see also Lattke, 2006).