Leptothorax ambiguus pinetorum

The type series of this species was found nesting in a small, hollow, dead root covered by pine needles on the edge of a dry piney bluff. Four colonies and several stray workers were taken in or near the type locality (Jackson County, Ohio, USA). All were small, comprising 10-25 workers. The second of these four consisted of a small hollow twig, another of a curled-up dead leaf, both just under the pine needles. The fourth colony was nesting in the bark of a pine log.

Distribution
Known only from type material from Jackson County, Ohio, USA.

Distribution based on Regional Taxon Lists
Nearctic Region: United States.

Nomenclature

 *  pinetorum. Leptothorax ambiguus var. pinetorum Wesson, L.G. & Wesson, R.G., 1940: 97 (w.q.m.) U.S.A. Combination in L. (Myrafant): Smith, D.R. 1979: 1392. Currently subspecies of ambiguus: Creighton, 1950a: 263.

Taxonomic Notes
Creighton (1950): In 1940 the Wessons recognized a variety of Temnothorax ambiguus to which they gave the name pinetorm. The principal differences between Temnothorax ambiguus foveatus and ambiguus are to be found in the more robust petiolar nodes and a slightly stronger impression of the sides of the thorax at the mesoepinotal suture in foveatus. According to the Wessons, the epinotal spines of pinetorum are notably longer than those of ambiguus and the thoracic rugae of pinetorum are feebler. In both cases the differences are clearly discernible only when the variants can be compared with the typical form. For this reason I have made no attempt to include either foveatus or pinetorum in the key. The problem of distinguishing between these variants and the typical ambiguus is by no means the only difficulty involved. We know practically nothing about the range of either insect. The two type specimens of foveatus were taken at Plainfield, Illinois. The type series of pinetorum and several other nests of this form came from Jackson County, Ohio. Since it has been customary to regard the range of the typical ambiguus as extending from eastern Canada and New England to the Dakotas, there is little present help to be secured from the occurrence of both foveatus and pinetorum at points approximately in the middle of this range. But it is by no means certain that the population which has previously been regarded as the typical ambiguus is a uniform one. It may be recalled that Emery utilized material coming from South Dakota, Ohio and New York as type specimens of ambiguus. In order to reduce confusion which might arise from a mixed type series, I propose to restrict the type series of ambiguus to those specimens which were taken in Hill City, South Dakota. There are two reasons why this is advantageous. Specimens from this same series, which are authentic and presumably cotypes, are present in three American museums. In the second place, if there is any tendency for ambiguus to produce geographical races, it may be safely assumed that the Hill City specimens represent the western race, for this station appears to be close to the western limit of the range of the species. Before anything certain can be stated as to the exact relationship of foveatus and pinetorum to the typical ambiguus it will be necessary to make a survey of the eastern population of ambiguus and determine to which of the three described forms this population belongs. Either foveatus or pinetorum may prove to be an eastern race of the typical ambiguus. I confess that it seems very unlikely that both will prove to be valid subspecies and perhaps both may prove to be inconsequential variations which lack any distributional significance. Until the matter can be definitely decided the two forms may be retained provisionally as subspecies.

Worker
Differs from Temnothorax ambiguus in the length of the propodeal spines and in the sculpture. The propodeal spines are longer in proportion to the mesosoma than in our specimens of T. ambiguus, the length of the spine divided by the length from the declivity of the pronotum to the base of the spine being 0.33 to 0.24 in T. pinetorum, while the corresponding ration in T. ambiguus is 0.24 to 0.15. The course longitudinal rugae on the thorax are less conspicuous in T. pinetorum.

Queen
Differs from the queen of T. ambiguus in smaller size and in the length of the propodeal spiens. The length is 2.5-2.9mm in T. pinetorum, 3.2-4.2mm in T. ambiguus. The propodeal spines are rather slender, twice as long as broad at the base; they are about as long as broad in T. ambiguus.

Male
Differs from the male of T. ambiguus in smaller size, 1.95-2.2mm (length of T. ambiguus male, 2.2-2.4mm), and in the fewer erect hairs on the surface of the body.