A detailed study of the holotype of Sphecomyrma canadensis Wilson, 1985 from Canadian amber has led to the conclusion that the specimen belongs to a new genus, here named Boltonimecia gen.n. Since the taxonomy of stem-group ants is not well understood, in order to find the taxonomic position of this genus, it is necessary to review the classification of stem-group ants in a study of their relation to crown-group ants. In the absence of data for traditional taxonomic approaches, a statistical study was done based on a morphometric analysis of antennae. Scape elongation is believed to play an important role in the evolution of eusociality in ants; however, this hypothesis has never been confirmed statistically. The statistical analysis presented herein lends support to the view that antennal morphology reliably distinguishes stem-group ants from crown-group ants to determine whether a species belongs to one or the other group. This, in turn, may indicate a relationship exists between eusociality and scape elongation. A review of Cretaceous records of ants is made and the higher classification of Formicidae with definitions of stem and crown groups is proposed. Newly obtained data are discussed focusing particularly on the origin, evolution and diversity of ants. Examination of the amber inclusion.Photographs were taken with a Nikon D1X digital camera attached to the microscope Leica Z6 APO. The photographs were used to make drawings, which were then computer generated and adjusted using Adobe Photoshop. All measurements were made with an ocular micrometer and are in millimeters. The following measurements were recorded: HL -head length (measured in full-face view as a straight line from the anterior-most point of median clypeal margin to the mid-point of the posterior margin of the head), HW -head width (maximum head width in full-face view), SL -scape length (maximum length excluding articular condyle) F1L-F9Llength of flagellomeres (1 st -9 th ), AL -antenna length, ML -mandible length (maximum length of its horizontal part), WL -Weber's length (the distance from the anterodorsal margin of the pronotum to the posteroventral margin of the propodeum), TL -total body length.Taxon sampling and morphometry. I used all morphometric data on antennae and heads of stem-group ants available from the literature; also I either made measurements or used published data on antennae and heads of crown-group ants representing all extant subfamilies ( Тable S1). For the measurements, only species with both a detailed description in the literature and high resolution images available from AntWeb (Fisher 2002) were selected. I also aimed that the species would cover the broad phylogenetic diversity. All subfamilies in the data set are represented by one species, except for the largest ones (Ponerinae, Dolichoderinae, Formicinae, Myrmicinae), which are represented by two species. Recently, six subfamilies of the dorylomorph group have been subsumed into a single subfamily, Dorylinae (Brady et al. 2014), but here in order to cover bro...

Based on field surveys, museum specimens, and published literature, we document 73 ant species in three subfamilies and 12 genera for the province of Saskatchewan, Canada. An additional 16 species are known from surrounding regions and are likely to occur in Saskatchewan.

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