Myrmica Species Groups of North America
The genus Myrmica is primarily a Holartic genus. These ants are a common element of the ant faunas of large parts of Europe and North America. Species identification can be difficult and frustrating. Radchenko and Elmes have been been steadily and consistently improving the taxonomy of the Palearctic species for more than 2 decades, with Seifert also making important contributions in this effort. Franceour has been studying the North American Myrmica for decades but little of his research has been finalized and published.
What follows are a few species groups that have been presented by Franceour for some of the North American species. These groups are 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.
Species group treatments for the rest of the world are found here: Myrmica Species Groups
This group contains two sister species. The females are characterized by the following combination of morphological characters. Head rounded. Clypeus not elongated, with anterior margin evenly convex. Eyes oval. Frontal lobes relatively wide, upwardly produced, with a strongly convex margin on nearly half of the length, follow carinae curving outwards to merge with front rugae; front area sagitally elongated. Scapes slightly shorter than head length; angularly bent basally, bend surrounded by a lamina small to spoonlike. Mesosoma profile convex with a promesonotal furrow very shallow; body coarsely striato-rugulose. Spines of medium length, shorter than the distance separating their tips, subdiverging. In lateral view metasternal flanges bilobate or bidentate from a thin rectangular base. Wings translucid. Western species occuring in dry and warm habitats.
This group includes three eastern species sharing the following exclusive combination of morphological characters for females. Clypeus elongate, with anterior margin angulo-convex. Frontal lobes laterally developed over the antennal socket as triangular or angulo-convex surfaces; frontal area transverse-rectangular. Eyes oval, of medium size. Antennal scapes evenly bent basally, smooth and shining, shorter than head length; base flattened dorsally. Mesosomal profile typically with a rather flattened promesonotum, higher than the propodeum; in dorsal view promesonotum pear-shaped, posterior end of mesonotum narrower and angulo-convex. In lateral view metasternal flanges shaped as inverted triangular lamellae. Petiole and postpetiole short. First gastric (fourth abdominal) segment with large, rounded piliferous punctures. Wings tinted brown. In addition their distribution occurs within the range of the same biogeographic biome: the northeastern deciduous forest.
Taken alone a character may not be exclusive to this group. Similar characteristics of the antennal scapes and the triangular shape of the frontal lobes also occur in the M. incompleta group. This latter group includes Myrmica incompleta, Myrmica alaskensis, Myrmica lampra and Myrmica quebecensis. The last two species are workerless parasites (Francoeur 1984). A third parasitic species, Myrmica semiparasitica, has retained the worker caste. Large gastral punctures exist also in Myrmica striolagaster.
Although M. punctinops is a Pacific coast species, inhabiting a very different ecobiogeographical range, it is provisionally included in the punctiventris group with which it shares the cephalic features. However, the mesosomal profile is quite different, similar to that of the crassirugis group, the first gastral segment lacks enlarged punctures, and the erect hairs of the gastral dorsum are longer than in the eastern species. The frontal lobes are similar to those of Myrmica alaskensis. Based on general examination of Palearctic species I believe that M. punctinops (together with another species) belongs to what I named a “Pacific ant fauna” in my Formica fusca group revison (Formica subelongata is an example) (Francoeur, 1972). This term is used to mean that there exist Nearctic species limited to the Pacific Coast of which equivalent forms occur in the Asiatic side of the Pacific ocean. Such a faunal trend is also observed for the genera Formicoxenus (Francoeur et al., 1985) and Temnothorax (unpublished). Such a phenomenon can be expected for ants as well in the history of the Holarctic region. A comparative study of this myrmecofauna should be most significative not only in terms of phylogeny, but also of evolutionary eco-biogeography.