Some interesting things happened this week. But first, let’s review the list of swarm locations. Swarms occurred in the following areas over the past week:
Fort Collins, CO
Marco Island, FL
Panama City Beach, FL (2 swarms)
Siesta Key, FL
Venus, FL (3 swarms)
Cape Elizabeth, ME
Port Tobacco, MD
Seaside Heights, NJ
New Braunfels, TX
West Jordan, UT
Yet another week of mediocre levels of activity, but I did see a few interesting things happen. Most importantly, there has been very little activity in Florida so far this year, but there was a lovely little surge this past week. I suspect it was because Hurricane Isaac was approaching. I can’t say for certain that the hurricane was the cause, but there is some good evidence that it was playing a role in the increase in activity. I was in Florida myself as Isaac approached, so I was able to make firsthand observations. I didn’t see swarms until the evening it got windy, cloudy, and the temperature dropped. Before you started to feel the effects of the storm, you didn’t see any swarms. After the first arms of the storm reached Archbold, suddenly there was swarming. I also received three reports of migratory swarms in which thousands of dragonflies were flying the wrong way for this time of year, coming north into Florida from over the water. The migration is upon us, so it is very strange to see swarms moving north when you expect to see them moving south. But, when you consider the gigantic swarm headed north from the same direction as the dragonflies, it suggests the dragonflies were responding to the hurricane’s approach.
Considering the similar patterns in swarming that were observed last year when Hurricane Irene hit the east coast, I’m going to tentatively suggest that hurricanes are major forces driving swarming behavior. I’ll have to see what happens after a few more hurricanes hit land in the US to say this with any sort of certainty, but the evidence suggests that this might be happening.
Also, I already mentioned this in my Friday 5 post from last week, but I got to add a new species to my list of confirmed swarming species last week. The more of these I add and the more countries where swarms are observed, the more it suggests that this is a rather universal dragonfly behavior and not simply a behavior of the known migratory species. (Hyacinth gliders could be migratory though – they’re very widespread.) They formed strange swarms too. They stayed in the same dense group as other species, but they flew differently within that group. Rather than doing the little rectangular or figure 8 flight patterns most commonly reported in other species, these were much more jerky in their flight, a lot less regular. They almost flew in little zigzags. They did, however, consistently do one thing over and over: they flew slowly straight into the wind, hovering several times as they advanced, then abruptly turned 180 degrees and flew 20 or 30 feet very quickly the opposite direction. Then they would turn around and do it all again, repeating this same motion for hours at a time. I haven’t seen anything like it in another species. It might be something unique to this species, though it might just be something no one has reported yet.
I could go on and on, but in the interest in getting this up on the blog sometime today, I’m going to leave you with a video of the hyacinth gliders swarming at Archbold during Bug Shot. I watched these swarms for a couple of hours altogether and they were truly magical!
Until next week!
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