Key to Pheidole tristis group

This worker key is based on:

This exclusively Neotropical group ranges from lowland Mexico to Argentina and throughout the West Indies. It rivals the other giant Pheidole assemblages of the New World, the diligens, fallax, and flavens groups, in its species diversity and magnitude of adaptive radiation. Like these other groups, it is vaguely bounded and connected to other assemblages by phenetically intermediate species. Nonetheless, a suite of traits allows reasonably secure placement of the great majority of species classified with the Pheidole tristis group in the present treatment. They include medium to large size, 4 or 5 hypostomal teeth, comparatively short antennal scapes in the major and moderately long ones in the minor, relatively small eyes set well back from the anterior genal border, and a mesonotal convexity either weakly developed or altogether absent. Also present among a third of the species are hornlike protrusions from the frontal lobes and mid-clypeal carina in the major caste and, in many, also decoration of the pronotum with conspicuous parallel transverse carinulae in the minor caste. Three very distinctive Cuban species (Pheidole alayoi, Pheidole macromischoides, and Pheidole naylae) as well as Pheidole avia and Pheidole bucculenta from Brazil, Pheidole bruchi from Argentina, Pheidole laeviventris from Colombia, Pheidole macracantha from Panama, Pheidole severini from French Guiana, and Pheidole microps and Pheidole minax from Peru, are so far known only from minor workers and are not included in the key that follows. However, they can be readily identified from the drawings and diagnoses provided in their individual species descriptions.

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 * Pheidole
 * "New World Pheidole" Wilson 2003

1

 * Very large species, Head Width of major about 2.6 mm and of minor 0.8-1.0 mm. Major: in side view, either the ventral profile of the postpetiole bulges forward to form a convexity (separate from the rest of the postpetiolar sternite) as large as the petiolar node, or else the ventral profile is covered with a dense brush of medium-length hairs . . . . . 2


 * Smaller species, Head Width of major usually under 2.0 mm and rarely over 2.5 mm. Major: ventral profile of postpetiole concave, straight, or convex, but if convex, the protrusion is much smaller than the postpetiolar node, and at most it bears 3 or 4 hairs . . . . . 3