Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
Minor worker: head length 0.62mm, head width 0.56mm, scape length 0.54mm, Webers length 0.78mm (n=1). Head somewhat flattened behind; promesonotum evenly arched, mesonotal suture absent; propodeal spines short, sharp, upturned; face smooth and shining, or with faint sculpture on vertex and stronger punctatorugose sculpture between eye and frontal carinae; katepisternum and side of propodeum punctate; dorsal pilosity abundant, long, flexuous; color red brown.
Major worker: head length 1.45mm, head width 1.27mm, scape length 0.61mm (n=1), CI 88-91 (n=3). Face punctatorugose on anterior half lateral to frontal carinae; areas beneath sweep of scapes shallowly foveolate; medial area between frontal carinae with parallel longitudinal carinae; posterior half of face smooth and shining; clypeus with prominent medial tooth, tooth laterally compressed, keel-like, concave shiny area on each side of tooth, bounded laterally by prominent carinae extending obliquely from base of frontal carinae; bases of frontal carinae not elevated; hypostomal margin with no medial tooth, pair of subtriangular teeth located close to midline, less than one quarter distance to recessed teeth flanking mandibles; dorsal pilosity abundant; head with abundant setae projecting from sides of head in face view.
Similar species: Pheidole JTL-110.
Costa Rica, Panama (type locality).
This species occurs in mature wet forest. It is very common in Winkler samples, and occurs in leaf litter up to the highest elfin forest in Monteverde. Nests have been found under loose bark of dead trees and in dead wood on the ground.
I recently separated low and high elevation forms of this species because the two forms were found sympatrically at two different mid-elevation sites in Costa Rica: the Volcan Barva transect at 500m elevation and the Peľas Blancas valley at the Poco Sol field station, at 800m elevation. I am guessing that the types of P. rhinoceros match the upland form, but cannot be certain until the types are examined. The types are from Bugaba, Panama. The lowland form is assigned the morphospecies code JTL-110 (the same morphospecies code used previously).
The related species JTL-110 has similar habitus, and the major worker has the same median clypeal keel or horn. JTL-110 differs in the major by having the clypeus with sharp median horn, single sharp lateral carina, and the interspace very smooth and shiny with no other carinulae, and strongly concave. The frontal carinae are strongly elevated and tooth-like. Also the head in face view appears a bit shorter and with more convex sides. P. rhinoceros has the median horn shorter, the lateral carina sometimes double, and the interspace duller, often with faint carinulae, and less concave. The frontal carinae are less strongly elevated. The head in face view appears somewhat larger and more quadrate. JTL-110 differs in the minor in having the katepisternum and side of propodeum largely smooth and shining. P. rhinoceros has these areas largely foveolate.
JTL-110 is very close to P. unicornis Wilson 2003, from a 2100m elevation site near Cali, Colombia. The P. unicornis major has the lateral clypeal carina low and less sharply defined; in lateral view the median clypeal horn is rounded; the inner hypostomal teeth are larger; and the head appears somewhat larger and relatively more elongate. The JTL-110 major has the lateral clypeal carina tall, sharp, and strongly differentiated from more lateral carinulae; in lateral view the median clypeal horn forms a distinct angle and is tooth-like; the inner hypostomal teeth are smaller; and the head appears somewhat smaller and relatively broader. The minors of the two are indistinguishable.
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. firstname.lastname@example.org
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