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

 * Node of petiole in lateral view strongly elevated, with an almost vertical posterior face. Anterior clypeal border unarmed, straight. Palp formula 2,2 => 2
 * Node of petiole in lateral view low and rounded, or triangular, without an almost vertical posterior face. Anterior clypeal border subconvex, rectangular or triangular. Palp formula 3,2 or 4,3 => 4

2

 * Mesosoma in profile not evenly convex, but flattened or indented at posterior third. Node of petiole in lateral view almost as wide at apex as at base. Total length > 3.7 mm. Frontal area broader than 1/3 of the maximum head width. Virginia into Florida, west into Illinois and Texas => Proceratium croceum


 * Mesosoma in profile evenly convex. Petiole narrower, or more like a truncated triangle. Total length < 3.5 mm. Frontal area at most slightly more than 1/4 of the maximum head width, or, if the frontal area is 1/3 of the maximum head width (P. mancum), then the mid and hind basitarsi with hairs about ½ of their length => 3

3

 * Second gastral tergite densely punctate and densely hairy, with most punctures only one or two puncture widths apart. Each frontal carina only slightly expanded laterally (about 1/4 of head width), and the flat area between the two carinae gently diverging posteriorly. New York into Florida, west into Mississippi and Arkansas => Proceratium crassicorne


 * Second gastral tergite sparsely punctate and hairy, with most punctures several puncture widths apart. Each frontal carina strongly expanded laterally (broader than 1/4 of head width), and the flat area between the two carinae strongly diverging posteriroly. Ontario south to Florida, west into Illinois and Texas => 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. Node of petiole in lateral view a rounded triangle with a distinct posterior face => Proceratium californicum


 * Propodeal suture absent. Clypeus anteromedially rectangular. Propodeal sides with lamellae. Long hairs suberect and distributed on the whole body. Node of petiole in lateral view smoothly rounded, not at all triangular => 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
into Iowa and Texas => Proceratium pergandei
 * Gaster short, opaque, with dense and short hairs. Second gastral tergite in lateral view broadly projecting rearward. Massachusetts south into Florida, west


 * Gaster longer, shinier, with sparse and longer hairs. Second gastral tergite narrowly protruding rearward. Florida, Georgia, Alabama => Proceratium chickasaw

7

 * Scapes surpassing the vertexal margin. TL ≥ 5.5 mm. Southeastern: Sandhills of northern Florida and southern Georgia => Proceratium creek


 * Scapes reaching the vertexal margin. TL < 5.0 mm. Southwestern: northern Mexico and south Texas => Proceratium compitale