Key to Temnothorax of California

A key to Temnothorax  workers of California. Based on Snelling, R.R., Borowiec, M.L. & Prebus, M.M. 2014. Studies on California ants: a review of the genus Temnothorax (Hymenoptera, Formicidae). ZooKeys 372:27–89. doi:10.3897/zookeys.372.6039

The following worker-based key includes the 20 species of Temnothorax known from California, plus two additional species (Temnothorax nuwuvi, Temnothorax carinatus) known from neighboring states to the east.

In California, Temnothorax can be most easily confused with Leptothorax, Tetramorium and Myrmica, but all these genera have at least six mandibular teeth. Additionally, Tetramorium and Myrmica possess mid- and hind tibial spurs. In western North America, workers of Temnothorax can be recognized by a combination of a waist consisting of two segments (petiole and postpetiole); postpetiole attached to anterior face of abdominal segment 4 (first gastral segment); absence of promesonotal suture from mesosoma; antennae 11- or 12-segmented and with differentiated 3-segmented club; eyes present and consisting of at least several facets; frontal carinae not laterally expanded or extending posteriorly past the eye; presence of median clypeal carina; clypeus elevated slightly above mandibles in profile view, not an anteriorly projecting lobe that fits tightly over the base of the mandibles; mandibles with five teeth; propodeal spines present at least as distinct tubercles and tibial spurs on middle and hind legs absent.

1

 * Antenna 11-segmented . . . . . 2
 * Antenna 12-segmented . . . . . 5

2

 * Propodeal spines longer than 0.5 × distance between their bases, PSI 19–30; pronotal dorsum coarsely areolate-rugose or at least irregularly rugose . . . . . 3


 * Propodeal spines dentiform, always much less than 0.5 × distance between their bases, PSI 6–10; pronotal dorsum dull and reticulate, without coarse areolae or rugae . . . . . 4

3

 * Petiole node profile subacute dorsally, with dorsal face rounding evenly into posterior face of node; petiole 0.97–1.04 times longer than high in profile when length is measured on a plane parallel to the venter of the petiole, from the anterior flange of the peduncle to the posterior margin of the petiole and the height is measured from the top of the node to the ventral margin of the petiole in a plane orthogonal to the length measurement; metafemur slender, 4.0–4.7 times longer than wide in dorsal view; groundnesting species, occasionally aboreal . . . . . Temnothorax rugatulus


 * Petiole node broadly rectangular, with an oblique angle between the dorsal and posterior faces of node; petiole 1.04–1.18 times longer than high in profile; metafemur stout, 3.5–4.2 times longer than wide in dorsal view; exclusively arboreal nesting species . . . . . Temnothorax caguatan

4

 * Head, especially posteriorly, with extensive smooth shiny areas; promesonotum often with smooth or weakly sculptured areas; summit of petiole node blunt in profile . . . . . Temnothorax whitfordi


 * Dorsa of head and mesosoma reticulate and dull; summit of petiole node acute in profile . . . . . Temnothorax oxynodis

5

 * Eye round to oval . . . . . 6


 * Eye elongate, approximately kidney-shaped . . . . . Temnothorax obliquicanthus

6

 * Mesosomal dorsum with metanotal groove impressed, pronotum distinctly higher than the base of propodeum . . . . . 7


 * Mesosomal dorsum without a distinctly impressed metanotal groove . . . . . 8

7

 * Dorsum of head and mesosoma slightly shiny and finely reticulate, without longitudinal rugae . . . . . Temnothorax paiute


 * Dorsum of head and mesosoma shiny between fine to coarse longitudinal rugae . . . . . Temnothorax myrmiciformis