Lasius peritulus

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)

Distribution
This taxon was described from.

Nomenclature

 * † peritulus. †Tetramorium peritulum Cockerell, 1927: 165 (m.) U.S.A. (Oligocene). Combination in Lasius: Carpenter, 1930: 58. See also: Wilson, 1955a: 58.

Queen
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.

Male
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.

Type Material
Wilson (1955) - HOLOTYPE. According to Carpenter, the unique type is a well preserved male now located in the British Museum.