Sunday, July 13, 2014

Blue-fronted vs Blue-tipped Dancers

I think I have a handle on identifying Blue-fronted and Blue-tipped dancers. These small damselflies are often very common on roadsides and forest paths. They are usually hardly noticed by casual hikers. I found both of these dancers along the road next to the river at the Cannon River Wilderness Area in Rice County, Minnesota.

Dancers are a large group of New World odonates. These two species are in the genus Argia. They are recognized by scientists by their long tibial spines.  I generally look for their habit of holding their wings high above their abdomens.

The top two photos are of Blue-fronted Dancers. On the blue male, note the very thin black stripe both on top and on the sides of the thorax. The last three abdominal segments are blue. Look closely at the eighth segment—it has a small black notch on it, a field mark often, but not always present on Blue-fronted Dancers. The female is harder to identify.  You may have to enlarge your view of the photo on your computer to note the pale tan stripe that runs across the sides of the last couple of abdominal segments.

The last two photos are of Blue-tipped Dancers. The male is “easily” identified by his broad purple thoracic stripes, whitish sides, and only having the last two abdominal segments blue. The female is tougher. Note that her last abdominal segment is pale.  Then look for a tiny tan triangle at the back of her dark thoracic stripe.

Just when a fellow thinks he has this identification riddle solved, along come blue-form females of both species. I will, for the time being, ignore those! In any case, both species fly for most of the summer, from June through August. Two good books for identifying damselflies are Bob Dubois’ Damselflies of the North Woods (if you can find it) and Ed Lam’s stunningly illustrated Damselflies of the Northeast.

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