Temporal range: Late Eocene Florissant, Colorado, United States
This is a Lasius s. s. species of the Florissant shales, which deposits are considered lower to middle Oligocene in age (MacGinitie, 1953) and the best North American counterpart of the Baltic amber so far as the preservation of insects is concerned. Despite the fact that these specimens represent finely preserved rock fossils, they are still far inferior to the amber material and cannot be determined accurately beyond placement within the niger-neoniger species group. (Wilson 1955)
This taxon was described from Florissant, Colorado, United States (Late Eocene).
The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.
- †peritulus. †Tetramorium peritulum Cockerell, 1927: 165 (m.) U.S.A. (Oligocene). Combination in Lasius: Carpenter, 1930: 58. See also: Wilson, 1955a: 58.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
Wilson (1955) - Of 129 specimens examined, 5 were in a position to show the basal angle of the mandible, which is the crucial diagnostic structure in the subgenus. Each of the 5 possessed a "niger-type" mandible (see under description of Lasius niger), with the basal tooth as large as the adjacent teeth and aligned with them. Although the material is too badly crushed to allow precise measurements, the total size appears small, toward the lower limit of the range of size variation in niger.
Wilson (1955) - Of 91 specimens examined, 5 showed the entire mandibular outline. In each case this was unmistakably the "niger type", with the masticatory border shallowly impressed in its distal half, the basal angle broadly rounded, and the preapical cleft lacking. Two other specimens showed only the basal angle, which was also broadly rounded. The total size is approximately the same as for the modern Nearctic populations of niger and Lasius americanus.
Wilson (1955) - HOLOTYPE. According to Carpenter, the unique type is a well preserved male now located in the British Museum.
- Carpenter, F. M. 1930. The fossil ants of North America. Bull. Mus. Comp. Zool. 70: 1-66 (page 58, Combination in Lasius)
- Cockerell, T. D. A. 1927. Fossil insects from the Miocene of Colorado. Ann. Mag. Nat. Hist. 9(19): 161-166 (page 165, male described)
- Wilson, E. O. 1955a. A monographic revision of the ant genus Lasius. Bull. Mus. Comp. Zool. 113: 1-201 (page 58, see also)