Monday, June 7, 2010

Boreal Bluet (Enallagma boreale)

Without having examined the claspers it's equally possible that this is a Northern/Vernal Bluet (Enallagma cyathigerum ssp.). This damselfly complex may be distinguished from other "blue type" damselflies, such as the Familiar Bluet, by the large ocular spots and relatively narrow humeral stripe. And although the cerci cannot be seen in detail in lateral view they are clearly much shorter than would be expected on a Familiar Bluet. However, the aberrant longitudinal spot on S5 isn't shown in either of my field guides. This damselfly is about 30 mm long.

Since the mesostigmal plates weren't examined this female could be either a Boreal or a Northern Bluet. We do know it's one or the other because, in addition to the large eyespots and tapering humeral stripe, blue-type females of these two species have a blue spot on the side of S8, often fused at the top as in the damselfly below.

The colors and patterns on the following damselfly are the same as the insect above. This time I was able to take a closeup of the terminal abdominal segments before the damselfly took flight.

This is a Boreal Bluet (Enallagma boreale). The cerci or upper claspers on a Northern/Vernal Bluet would have a hook sharply upturned at the tip.