This summer, REU student Jill Gall collected ants from prairie remnants in Douglas County. Part of her project was identifying specimens to genus and sorting them by morphospecies (i.e. you know they're different species, but you don't know which species they are). This fall I met with Dr. Sean Menke, an ant ecologist at Lakeforest College, to look at the specimens she collected and get advice about how to identify ants. His advice has helped me make move forward in identifying the specimens we collected this summer.
The challenge with distinguishing ant species is that a lot of the most obvious characteristics, such as size and color, vary within species. The traits that do distinguish species vary across genera. For instance, in the genus Formica, species can be discerned based on the hairs covering certain parts of the body and the glossiness of certain body parts. In Lasius, one of the key traits is the orientation of the hairs on the antennal scape (the part of the antenna closest to the head). With some genera, species identification is especially difficult. One of these is the genus Myrmica.
After looking through a large number of specimens, I have come across four types that I believe are separate species. The differences are in the shape of the antennal bend and in the shape of the flange that covers the base of the antennae. I have circled this area in the pictures below. For three of the four morphospecies, I have included pictures of two individuals. See if you can spot the differences.