I’ve always thought dragonflies were some of the prettiest insects to watch. They’re not as spectacular as butterflies, but more graceful in flight. Walking along the “school path” (a gravel path through a wetlands area between our neighborhood and the elementary school) in the town where I grew up, I could usually count on seeing dragonflies and damselflies skimming over the water.
It doesn’t surprise me at all to see them around the pond at the nearby park, or at the pond where my company holds its annual children’s fishing derby each August. What did surprise me this evening was to see swarms of dragonflies around the treetops and telephone poles and wires, as Al and I took a walk around the neighborhood.
I’m more often looking down than up when we walk, as interesting things are more likely to be on the ground than in the air, but the unusual number of small flying creatures in the air caught my eye. They seemed too big to dragonflies, since I could make them out easily even so high above my head, but the ones that were closest were clearly too small to be birds. I could see nothing in the area that drew them there, but they continually looped around the area over the driveway we were passing.
Finally, mystified, we walked on. And I saw another swarm of them ahead, this time over a tree. Looking further, I saw more over another tree. And another. Each group stayed around its own tree – or set of telephone wires. I saw trees that didn’t have any, but I couldn’t see any pattern to explain why some trees had them and others didn’t.
I’d never seen dragonflies swarm before, and I couldn’t remember seeing any flying at treetop height before – though if they hadn’t been swarming I doubt I would have noticed them. I made up my mind to go online and see what I could learn to explain their behavior.
I quickly learned that it’s not unusual behavior – and also not unusual for people to go online wondering what caused that behavior. I also learned that there are several kinds of dragonflies, and that the kind my son and I saw this evening are most likely darners. These are among the largest dragonflies, and they do tend to fly at treetop height, and keep flying around rather than landing.
I also found out that they most likely were feeding. While I couldn’t see anything in the area to attract them, they no doubt could see the tiny insects that I could not. We’ve had a great deal of rain this summer, and a lot of hot muggy days in between. (By the time we took our walk this evening the temperature had dropped to 86 degrees, but the heat index was still 99.) I don’t know if that has produced an unusually large population of whatever insects these darners eat, but it seems a reasonable explanation.
One of the first websites I found was The Dragonfly Woman’s blog, specifically a post about dragonfly swarms. She asks readers to contribute information about swarms they have seen, so she can add them to her database to try to see patterns of where and when and under what conditions they are seen. I added mine; if you’ve seen some you can contribute your observations also.