Key to US Proceratium species

The following key to the Proceratium workers of the United States has been modified from Baroni Urbani & de Andrade (2003). For all North and South American species see the Key to Nearctic and Neotropical Proceratium species.

1

 * Petiole rectangular. Anterior clypeal border unarmed, straight. Palp formula 2,2 => 2
 * Petiole convex. Anterior clypeal border subconvex, rectangular or triangular. Palp formula 3,2 or 4,3 => 4

2

 * TL > 3.7 mm. Frontal area broader than 1/3 of the maximum HW => Proceratium croceum


 * TL < 3.5 mm. Frontal area at most slightly more than 1/4 of the maximum HW, or, if the frontal area is 1/3 of the maximum HW (mancum), then the mid and hind basitarsi with hairs about ½ of their length => 3

3

 * Frontal area about 1/4 of HW and the carinae gently diverging posteriorly. Standing hairs on the postpetiole and gaster sparse and short => Proceratium crassicorne


 * Frontal area broader than 1/4 of HW and the carinae strongly diverging on the two anterior thirds. Standing hairs on the postpetiole and gaster denser and longer => Proceratium silaceum

4

 * Propodeal suture impressed. Clypeus anteromedially triangular. Propodeal sides without lamellae. Long hairs subdecumbent or decumbent, rare on the antennae and absent from the legs => Proceratium californicum


 * Propodeal suture absent. Clypeus anteromedially rectangular. Propodeal sides with lamellae. Long hairs suberect and distributed on the whole body => 5

5

 * Scapes much short of the vertexal margin. First funicular joint about 1/5 longer than broad. Funicular joints 2-10 about as long as broad or slightly broader than long. Mid basitarsi shorter than fore basitarsi. First gastral tergite strongly angulate on the curvature => 6
 * Scapes reaching or surpassing the vertexal margin. First funicular joint 1/2 longer than broad. Funicular joints 2-10 longer than broad. Mid basitarsi as long as or longer than fore basitarsi. First gastral tergite at most weakly angulate on the curvature => 7

6

 * Gaster short, opaque, with dense and short hairs => Proceratium pergandei


 * Gaster longer, shinier, with sparse and longer hairs => Proceratium chickasaw

7

 * Scapes surpassing the vertexal margin. TL ≥ 5.5 mm. => Proceratium creek


 * Scapes reaching the vertexal margin. TL < 5.0 mm. => Proceratium compitale