Comprehensive DescriptionRead full entry
Leptothorax (Mychothorax) canadensis calderoni Creighton HNS 1950a: 276. [First available use of name.] Three syntype workers, one syntype alate queen, Lake Tahoe , California , 6325' ( Calderon ) [ MHNG ] [Examined]
Comments. Leptothorax calderoni HNS is a large, bicolored species with short standing pilosity and a robust petiole. In California it is sympatric with another species in the L. muscorum-complex HNS , here called Leptothorax HNS sp. CA-01 (this second species might correspond to L. canadensis Provancher HNS ). In contrast to Leptothorax HNS sp. CA-01, the petiole of L. calderoni HNS has a less peaked appearance, with the anterior and dorsal faces forming a right angle in lateral view. The two pairs of standing hairs visible in profile on the dorsum of the petiole are separated by notably more than their lengths, whereas in L. sp. CA-01 HNS they are separated by about their lengths or less (compare Figures 5 and 6). In addition, L. calderoni HNS is larger (worker HW 0.66-0.81; n = 35) with disproportionately longer legs (worker FL 0.56-0.66; n = 35) compared to L. sp. CA-01 HNS (worker HW 0.56-0.70, worker FL 0.44-0.56; n = 70). The mesosoma, petiole and postpetiole of L. calderoni HNS are orangebrown, the head medium brown and gaster dark brown. Color contrasts tend to be less marked in L. sp. CA-01 HNS .
Most records of L. calderoni HNS come from coniferous forest at moderate to high elevations in the Sierra Nevada of California (1470-2680 m), with outlier populations in the northern Coast Ranges and in the San Bernardino Mountains of southern California. Colonies are found in cavities in hard, dead wood. Workers are often conspicuous as foragers on downed logs.
Bolton (1995b) incorrectly listed L. calderoni HNS as an unavailable name, overlooking that fact that Creighton’s (1950a) treatment of it as a trinomen rendered it available. Creighton considered L. calderoni HNS to be a subspecies of L. canadensis HNS and a senior synonym of L. canadensis septentrionalis Wheeler HNS (1917a). Actually L. c. septentrionalis HNS would have seniority if the two were synonyms, but they are not conspecific. They have a similar color pattern but L. c. septentrionalis HNS (described from Banff, Alberta and Emerald Lake, British Columbia) has longer setae, a more peaked petiole, and is smaller in size (syntype workers in MCZC examined).