The bluets form a group of about 17 similar species in Wisconsin in which the males usually share the characteristics of having blue and black stripes on the thorax, and blue and black markings on the abdomen. In-hand examinations are usually needed to identify them, although they can be grouped into subcategories based on the amount of black showing on the abdomen. Males are easily identified, under magnification, by the shape of their terminal appendages. Females are generally duller than males, and they are more difficult to identify, which is accomplished by subtle differences in the shape of the mesostigmal plates on the top of the thorax. Generally, males are bright blue while the females are green or yellow-green or blue. There are some species that are yellow-orange, a mix of various colors, or black with some blue.
The male of this species is a blue-type bluet because of its predominantly blue abdomen. It is very similar to the Hagen's bluet in the field. The female is tan to green instead of blue. The body length of the marsh bluet varies from 1.0 to 1.3 inches.
Throughout northern United States and southern Canada, the marsh bluet is usually found in marshes, vegetated ponds, lakeshores, and quiet streams. This species generally are not found in acidic conditions. It is very common and widespread throughout Wisconsin.
Early June to early September in Wisconsin.