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

8

 * First gastral tergum moderately to slightly shiny, most of disc distinctly finely sculptured . . . . . 9


 * First gastral tergum smooth and shiny, appearing polished, devoid of sculpture other than scattered minute piligerous punctures . . . . . 10

9

 * Head and mesosoma reticulate and dull, without longitudinal rugae; propodeal spines broad at base (in profile) and slightly less than the distance between their bases, PSI 14–17 . . . . . Temnothorax anaphalantus


 * Head and mesosoma reticulate and dull between distinct longitudinal rugae; propodeal spines slender and distinctly longer than distance between their bases, PSI 22–29 . . . . . Temnothorax morongo

10

 * Dorsal mesosomal profile flat or weakly convex; mesosoma slender and distance from dorsal mesonotal margin to base of mesocoxa 0.30–0.34 × WL; eye oval and EL at least 0.8 × OMD . . . . . 11


 * Dorsal mesosomal profile distinctly convex; mesosoma compact and distance from dorsal mesonotal margin to base of mesocoxa 0.5 × WL; eye round and EL about 0.7 × OMD . . . . . Temnothorax quasimodo

11

 * Petiole node triangular to subtriangular in profile . . . . . 12


 * Petiole node rounded to rectangular in profile . . . . . 15

12

 * Propodeal spines as long as, or longer than, distance between their bases, PSI 20–26; arboreal species nesting in galls and dead twigs . . . . . Temnothorax gallae


 * Propodeal spines distinctly shorter than the distance between their bases, PSI 10-16; arboreal or ground nesting species . . . . . 13

13

 * Color dark brown; propodeal spines reduced to slight angles, much shorter than distance between their bases, PSI 4–5; arboreal nesting species . . . . . Temnothorax arboreus


 * Color yellowish brown to brown; propodeal spines present and acute in profile, up to one-half the distance between their bases, PSI 10–16 . . . . . 14

14

 * Head reticulate and with variably extensive smooth shiny areas; mesosomal dorsum weakly to moderately reticulate, pronotum often shinier than propodeal dorsum; ground nesting species . . . . . Temnothorax nitens


 * Head uniformly reticulate but with smooth shiny median stripe; entire mesosomal dorsum strongly reticulate . . . . . Temnothorax chandleri

15

 * Propodeal spines as long as, or slightly shorter than the distance between their bases, PSI 15–24; light to dark brown ground nesting species . . . . . 16


 * Propodeal spines distinctly shorter than the distance between their bases, PSI 4–17; either arboreal or ground nesting; color variable . . . . . 17

16

 * Mesosomal dorsum reticulate, often appearing lineoreticulate, sometimes with weak longitudinal rugae; petiole node, in profile, less robust . . . . . Temnothorax nevadensis

Note: As presently understood, Temnothorax nevadensis is a variable species, occurring over a wide range of habitats (Wheeler and Wheeler 1986), and its taxonomic status is in need of further study (see also Ward 2005: 16).


 * Mesosomal dorsum reticulate between moderately coarse longitudinal rugae and usually promesonotum partly coarsely areolate; petiole node, in profile, more robust . . . . . Temnothorax rudis

17

 * Postpetiole wide, PPW 1.47–1.98 × PTW . . . . . 18


 * Postpetiole narrow, PPW 1.23–1.43 × PTW . . . . . 21

18

 * Postpetiole narrow relative to petiole, PPW 1.47–1.76 × PTW; mesosomal dorsum reticulate and variously rugulose in part, but not coarsely areolate with microreticulate interspaces . . . . . 19


 * Postpetiole wide relative to petiole, PPW 1.79–1.98 × PTW; pronotal disc and dorsal face of propodeum coarsely areolate with microreticulate interspaces . . . . . Temnothorax wardi

19

 * Postpetiole dorsum reticulate and dull; head shiny and with weakly defined fine rugulae, but extensive areas without rugae . . . . . 20


 * Postpetiole shiny between weak punctures and with medial impunctate area; head with distinct coarse longitudinal rugae, interspaces variably reticulate . . . . . Temnothorax nuwuvi

20

 * Mesosomal dorsum with variably extensive smooth areas, otherwise reticulate; propodeal spines acute in profile and, when viewed obliquely from above, surface between them nearly flat; dark brown species . . . . . Temnothorax neomexicanus


 * Mesosomal dorsum reticulate; propodeal spines robust in profile, nearly right angular at tips and, when view obliquely from above, surface between them approximately semicircular; light brownish yellow species . . . . . Temnothorax carinatus

21

 * Cephalic venter with scattered fine setae; frons, in profile, with short setae present along entire length, from base of clypeus to posterior margin . . . . . Temnothorax andrei


 * Cephalic venter without setae; frons, in profile, with few or no setae, but with 2 on lower vertex and 4 across posterior margin . . . . . Temnothorax pseudandrei