Temnothorax arboreus, Snelling, Roy R., Borowiec, Marek L. & Prebus, Matthew M., 2014

Snelling, Roy R., Borowiec, Marek L. & Prebus, Matthew M., 2014, Studies on California ants: a review of the genus Temnothorax (Hymenoptera, Formicidae), ZooKeys 372, pp. 27-89 : 32-33

Temnothorax arboreus sp. n. Figures 5, 19, 24-26

Temnothorax sp. CA-09; Ward 2005: 68.

Diagnosis of worker.

Promesonotum flat, followed by sloping dorsal face of the propodeum, so that in lateral view propodeal angles are relatively low on the declivity; head shiny, varying from weakly sculptured to smooth; petiole node robust and triangular in profile; propodeal spines reduced to small angles; body color dark brown.

Description.

Worker measurements (mm) (4 measured): EL 0.128-0.142 (0.136); HFL 0.201-0.444 (0.371); HFW 0.101-0.123 (0.112); HL 0.584-0.652 (0.614); HW 0.475-0.534 (0.502); IOD 0.416-0.453 (0.435); OMD 0.151-0.187 (0.168); PPW 0.197-0.217 (0.206); PSL 0.025-0.034 (0.030); PTW 0.136-0.151 (0.143); PW 0.328-0.369 (0.347); SL 0.395-0.447 (0.425); WL 0.647-0.761 (0.702). Indices: CI 79.6-85.6 (81.8); FI 83.1-84.4 (83.9); OI 21.6-23.0 (22.1); PI 142-145 (144); PSI 4.28-5.21 (4.88); SI 67.6-71.3 (69.2).

Head longer than broad in frontal view, lateral margins very weakly curved, posterior margin flat to weakly curved. Antennal scape ending below posterior margin by more than its apical width; apical club distinctly 3-segmented. IOD 3.04-3.33 × EL; EL 0.75-0.91 × OMD. Mandible finely longitudinally rugose. Clypeus with 1 or 2 short fine carinae on either side of median carina. Dorsum of head shiny, mostly smooth between scattered fine piligerous punctures; area around frontal carinae moderately shiny and weakly reticulate; malar area with several short fine longitudinal rugae, interspaces dull and sharply reticulate; posterolateral angles of head moderately shiny and weakly reticulate. Dorsum of head with sparse short, fine setae.

Mesosoma slender, WL 1.97-2.11 times longer than PW; mesosomal dorsum nearly flat in profile before sloping down to obtuse propodeal denticles. Mesosomal dorsum moderately shiny and weakly reticulate but pronotum posteriorly with transverse smooth band; side of pronotum moderately shiny and irregularly rugulose, interspaces inconsistently reticulate; posterior face of propodeum dull and reticulate. Metafemur 3.54-3.97 times longer than wide in dorsal view. Entire length of dorsum with>20 flattened setae that are distinctly longer than those of frons.

Petiole without anterior peduncle; node robust and subtriangular, no higher than thick, summit subacute; subpetiolar tooth short and acute. Postpetiole profile low; in dorsal view node 1.42-1.45 times width of petiole node. Both segments moderately shiny and mostly finely reticulate. Each node with 4-6 setae similar to those of mesosoma.

Gaster in dorsal view 2.86-3.02 times wider than postpetiole; disc of first tergite smooth and shiny between sparse piligerous punctures; disc with sparse suberect flattened setae similar to those of mesosoma and scattered finer prostrate pubescence.

Head and body dark brown, gaster darker posteriorly.

Gyne and male unknown.

Material examined.

Holotype worker, U.S.A.: CALIFORNIA: San Diego Co.: Wooded Hill, 3 km SW Mount Laguna, 1800 m, 32.85°, -116.43°, 26.v.2004 (P. S. Ward #15254), on low vegetation [beating on Pinus jeffreyi foliage], Pinus jeffreyi forest (CASENT0339243) [UCDC].

Paratypes. Same data as holotype, 1 worker (CASENT0339243) [PSWC], 2 workers (CASENT0339244) [UCDC].

Non-paratypic material examined. U.S.A.: CALIFORNIA: Riverside Co.: San Jacinto Mountains, Idyllwild, 1610 m, 33.7°, -116.7°, 10.vii.1962 (C. O. Eads) on trunk of Pinus jeffreyi , 4 workers (CASENT0005933, LACMENT299357, LACMENT299356, LACMENT299355) [LACM].

Etymology.

From Latin, arboreus - of trees, in reference to this being an arboreal species.

Remarks.

This species is similar to Temnothorax nitens ( Emery 1895) and in the key by Mackay (2000) it will run, with some difficulty, to Temnothorax melinus ( Mackay 2000), a synonym of Temnothorax nitens ( Ward 2005). From Temnothorax nitens it differs in the much darker color, the obtuse propodeal denticles that are shorter than the subpetiolar tooth, and the considerably more robust petiole node (Figure 19B & 21E).

As the name suggests, Temnothorax arboreus is an arboreal species. Workers have been collected from the trunk and beaten from foliage of Pinus jeffreyi . That this ant is arboreal further distinguishes it from Temnothorax nitens , a species that nests in soil, often under small covering objects such as stones.

A couple of collections of similar species are known from southeastern Arizona, but we feel the relationship of these samples will be better understood only when more material becomes available.