Key to Myrmica of the punctiventris group
This worker key is based on: Francoeur, A. 2007. The Myrmica punctiventris and M. crassirugis species groups in the Nearctic region. Pages 153-186 in R. R. Snelling, B. L. Fisher, and P. S. Ward, editors. Advances in ant systematics (Hymenoptera: Formicidae): homage to E. O. Wilson - 50 years of contributions. Memoirs of the American Entomological Institute, vol. 80, Gainesville, FL, 690 p.
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M. punctiventris group: Antennal scapes seen in profile evenly downcurved basally, base without any outgrowth. Clypeus entire and prominent, median anterior margin angulo-convex. Frontal lobes laterally developed over head dorsum into an angular surface with rounded angle. Eyes oval. In dorsal view promesonotum pear shaped, posteriorly angulo-convex, distinctly higher than propodeum in profile. First gastric segment with coarse, round punctures. If without such punctures, mesosomal profile is convex.
- First gastric segment with coarse, large piliferous punctures; mesosomal dorsum profile weakly convex to almost flat (eastern North America) . . . . . 2
- First gastric segment without coarse, large punctures; mesosomal dorsum profile convex; length of longest erect hairs on gaster dorsum equal to or longer than greatest diameter of eye (California) . . . . . Myrmica punctinops
- Propodeal spines elongated with a narrow, thin base; spine index < 1.5; subpetiolar process small and dentiform (larger species with normal queens . . . . . 3
- Propodeal spines short and dentiform with a large, thick base; spine index > 1.5; petiole sternal process lamelliform (smaller species with microgynes; parasitic species associated with Myrmica punctiventris) . . . . . Myrmica semiparasitica
- Dorsal surface of head coarsely striated; rugae high and thick with flattened top in cross section; frontal lobes smaller, difference between maximum and minimum width usually < 0.12 mm; propodeal spines distinctly longer than the distance separating their tips, usually deflected . . . . . Myrmica punctiventris
- Dorsal surface of head delicately striated, rugulae low and rounded in cross section; frontal lobes larger, difference between maximum and minimum width usually > 0.12 mm; propodeal spines shorter, about equal to the distance separating their tips, usually straight . . . . . Myrmica pinetorum