How to identify a dragonfly

I saw a brightly colored dragonfly perched nicely on the trunk of a tree and thought it would be easy to identify because its colors were so distinctive.

What is that the dragonfly has captured and is eating?

What is that the dragonfly has captured and is eating?

A closer look…yes indeed, this one is eating another dragonfly, probably a meadowhawk.

It's already devoured the head and part of the thorax of the meadowhawk.

It’s already devoured the head and part of the thorax of the meadowhawk.

After consulting my field guide (Dragonflies through Binoculars), I learned that this was one of a complex of 20 species of Mosaic Darners — named for the mosaic of spots on their abdomen — “many of which look alike and present a challenge for field identification.”  So much for an easy ID.

Maps of the distributions of the probable 20 species yielded 4 that could be found in MN currently, so I compared those side-by-side with my specimen using photos posted on the web.  The most important distinction seemed to be a side-view look at the thoracic stripes, which I didn’t really have among my photos from the field. (Note to self:  take more photos from different angles next time.)

They all look pretty similar.  But looking closely, there are some important differences.

They all look pretty similar. But looking closely, there are some important differences in the pattern of thoracic stripes.  Click on this composite to get a slightly larger image.

Complicating this identification somewhat is the variability of some of the species over their range, or even within their range (hence, the name Variable Darner!).

Using my two photos above, and the composite of the four species, I decided this must be a Canada Darner, (Aeshna canadensis), based on the square notch in the top (dorsal side) of the anterior thoracic stripe.  None of the others had this unusual patterned stripe.

So, a pretty minute little detail makes the difference between these otherwise very similar species.  Do you think a female really notices this?

Some of the important characteristics used to identify dragonflies.

Some of the important characteristics used to identify dragonflies.

7 thoughts on “How to identify a dragonfly

  1. Very enjoyable posting, Sue. It was interesting to see your approach to identifying the mystery dragonfly–it’s much more systematic and scientific than the way I tend to do it, which is by looking at different images and subjectively making a choice. Your dragonfly and your shots of it are wonderful. Most of the darners that I see are Common Green Darners, which rarely seem to perch. The remaining portion of the prey looks a bit like the Autumn Meadowhawk that I have been searching for, but there are other red-colored Meadowhawks too, so it’s hard to be sure. I like the way that you labeled the areas of the dragonfly to pay attention to when identifying them–that may prove helpful in focusing my attention.

    • Initially, I was terribly confused about which species I had photographed, and kept bouncing back and forth in choosing which one it was…until I compared those photos from the web side by side and finally started to see the differences. Took a looooong time, but I love a challenge. Thanks for your comments. I hope the approach helps you ID your dragonflies.

  2. Splendid shots! And unusual too with the smaller dragonfly prey. I am hopeless about identifying my subjects, apart from the few I know well because I see them often. Spiders really confuse me, as you may have noticed!

    • Some are, but I find that I need to know what to look for to be sure of the ID. I am still confused by some of the goldenrod species, and many of the yellow composites as well.

  3. Pingback: Beautiful Insects |

Please Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.