Even though I have learned to identify many dragonflies pretty well, I often feel clueless when it comes to damselflies. The differences between damselfly species are often subtle and difficult to see. I often get lost in trying to look at the relative size of eye spots or the length of various markings.
Fortunately for my self-esteem, there are some damselflies that I can confidently identify, like this female Ebony Jewelwing damselfly (Calopteryx maculata) that I spotted on Tuesday at Occoquan Regional Park. Ebony Jewelwings are the only damselfly species in our area with distinctively dark wings. It is even easy to distinguish the genders too, because only the females have white stigmas on each of their wings.
I was a little surprised this morning to learn that the male Ebony Jewelwings also have stigmas on their wings, but the stigma are black and do not show up very well on their black wings. According to a posting on the Nature Watch blog, “All damselflies (and dragonflies) have stigmas on their wings. A stigma (pterostigma) is a large, thick cell on the leading edge of the wing near the tip which helps stabilize the wing while the dragonfly or damselfly is in flight. It holds down vibration allowing increased speed during gliding flight. In many species the stigma is pigmented, in others, it is clear. Each wing has a stigma.”
I previously knew about stigmas, of course, but somehow thought of them as primarily decorative rather than functional elements. It is really cool to learn more about the physics of how that my magical little friends are able to fly. What really blows my mind, though, is thinking about how the world looks to them when viewed through their large, multi-faceted compound eyes. Wow!
© Michael Q. Powell. All rights reserved.
Read Full Post »
Mike Powell 