Temnothorax ambiguus ( Emery, 1895 )

Shattuck, Steve & Cover, Stefan, 2016, Taxonomy of some little-understood North American ants (Hymenoptera: Formicidae), Zootaxa 4175 (1), pp. 10-22 : 19-20

Temnothorax ambiguus ( Emery, 1895)

Leptothorax curvispinosus ambiguus Emery, 1895: 320 . Syntype workers, Hill City [43°56′N 103°34′W] , South Dakota, 8 July 1890 (Pergande) [https://www.antweb.org/specimen/CASENT0904763]; Cleveland [41°28′N 81°40′W] , Ohio (Wasmann) ; New York [40°44′N 73°56′W] , New York (Schmelter) (Museo Civico di Storia Naturale, Genoa).

Leptothorax foveata Smith, M.R., 1934: 211 . Holotype worker, Plainfield [41°36′N 88°12′W], Illinois, 25 May 1933 (Mary Talbot) (National Museum of Natural History, not seen). New synonym.

Leptothorax ambiguus pinetorum Wesson & Wesson, 1940: 97 . 12 worker, 1 dealate queen, 2 alate queen, 5 male syntypes, Jackson County [39°01′N 82°37′W], Ohio, 10 July 1938 (not seen). New synonym.

Smith (1934) described T. foveatus based on a single worker from Illinois. At the time he considered it “so different from all of the Leptothorax [now Temnothorax ] with which I am familiar that I am somewhat hesitant in trying to assign it to its proper taxonomical position.” However, some time later he reconsidered this view and Creighton (1950) reports that Smith “now regards the insect which he described as the species foveata in 1934 as very closely related to ambiguus if not actually a synonym of that species.” We concur with Smith’s later interpretation and consider T. foveatus to be a synonym of T. ambiguus . Note that Smith had two workers of this taxon, one of which was clearly abnormal. The abnormal worker has been imaged and placed in the USNM’s Ant Type database. The description makes clear that Smith did not consider it a type. Excepting its deformity in the structure of the petiole and postpetiole, it is otherwise a typical worker of Temnothorax ambiguus .

Wesson & Wesson (1940) established T. ambiguus pinetorum from specimens collected in Ohio, separating it from T. ambiguus based on the longer propodeal spines and less conspicuous mesosomal rugae. The queen and male were also described, the queen being separated from the queen of T. ambiguus by its smaller body size and longer propodeal spines, while the male was reported as differing from T. ambiguus in being smaller and less hairy.

Modern collecting has revealed T. ambiguus to be a geographically widespread species. There is variation in propodeal spine length, color, and queen size, and this is accompanied by comparable (but independent) geographic variation in nest site preference, colony size, and habitat selection. In the context of this bigger picture, the characters cited by Wesson & Wesson (1940) fall well within the observed variation in T. ambiguus . The types of T. pinetorum appear to come from a colony where the workers have somewhat longer propodeal spines and finer mesosomal sculpturing than average. Because of this we have no hesitation in considering T. pinetorum to be a junior synonym of T. ambiguus .

This taxon is known to occur from eastern and central Canada south to New Jersey, the Great Lakes region, and the northern Great Plains in the United States .