Sunday, May 31, 2015

What's happening right this minute.

The eastern United States is the only place you can see periodic cicadas. They are one of the world's marvels, but the catch is you can only see them every few years, and then for only a few weeks. There are three species of seventeen-year cicadas, and four species of thirteen-year cicadas. As I'm sure you all know the name stands for the number of years they spend underground as nymphs sucking the juice out of tree roots. There must be so many millions of them it is another marvel that the trees survive. They don't all emerge together on the thirteenth or seventeenth year. All those in a certain population do, but the generations are staggered. They are so well studied that all the differing populations have been named and numbered, so that biologists can say almost to the day when population XI or whatever will come out of the ground, change into adults (leaving their thousands of exuviae hanging to trees and bushes) and the males start singing to attract mates. That's still another marvel, their loud voices constantly in hearing over sometimes a square mile.

We learned early this year that thirteen-year cicadas would be emerging this summer in parts of Arkansas. So I wasn't surprised when, a few days ago, I arrived in Craighead Forest Park in Jonesboro, turned off my engine and opened the door to hear that sound. It was the first time in years.

They were some distance away, and I was in a hurry that day, so I didn't pursue them. But the next day Cheryl and I went to another area where we had seen them in the past, Lake Hogue in Bayou de View WMA in Poinsett Co. Sure enough they were singing at full volume when we arrived. There seemed to be at least two songs going, a high pitched melodic one which appeared to be constant on the same tone, and then a raspier one that surged up and down in volume. We walked a dirt road and saw them flying out from the tops of the trees like swarming bees. Their life as mating adults is so short we were already finding dead and dying on the road and picked up a dozen or so to take home and study. They were different sizes and slightly different colors. We knew there could be up to four species but we had no idea what to look for to try to separate them.

We had looked them up before and only found charts with roman numerals to designate the different populations and cohorts and emergence dates and it was so confusing that it made our (or anyway my) head swim, which is why we had never got anywhere trying to sort them out. But this time Cheryl made us stick to it and try to get some bearings, and we made a second trip and took photographs more intelligently and collected specimens with a better idea of what we were looking for, and we believe we found all four species. (However this was our first attempt at identifying the species, the color differences are subtle, the dead specimens perhaps changing color rapidly.)

Here's what we found, and here is our rationale, but keep in mind that our voice is very tentative.

If you have ever seen them, you will remember their dramatic appearance: big shiny black insects with bright red eyes and yellow veins on their large wings (they should only emerge during Halloween). Look at this first one.

Here the critical thing to look for is the orange spot directly behind the eye. Next let's look at it from another angle.

The underside of the abdomen is pale orange or yellowish. If we are correct, this is Magicicada tredecim, which is a more scientific way of saying "thirteen-year cicada."
Now look at this mating pair.

One is dangling unceremoniously off the branch, but after waiting thirteen years for this moment nothing is going to make them let go.  On the sitting one you see a brown spot behind the eye; on the dangling one a highly contrasting banded underbelly.

Here they have regained their position and a little dignity. You can see on both of them the brown spot behind the eye, which I think is quite different from the orange spot behind the eye of the previous example. Again if we are correct, this is Magicicada neotredecim.

Those are large cicadas. The next two I'm going to show you are noticeably smaller. First, here is an all black one. (In the hand the eyes on this one were still reddish, though the camera has not picked that up.)

No colored spot behind the eye, no yellow bands on the abdomen. This, we believe, is Magicicada tredecassini. And finally, this slightly different species, all black, but with narrow orange banding on the abdomen.

We believe this is Magicicada tredecula.

These are active in Arkansas right this minute. If you are driving through dense deciduous woods, stop from time to time to listen. If you hear them (you can't miss the sound) get out and observe them. It will be a long wait before you see them again. Only thirteen-year cicadas are out in Arkansas this year. In some other states (Kansas, for instance), I believe there are some seventeen-year cicadas around. I think our corner of northeast Arkansas might be especially good for finding all four thirteen-year species together. I don't actually know if we get any seventeen-year cicadas.

There are three species of seventeen-year cicadas, each one a sister species (some would say the same species) to one of the thirteen-year cicadas, and it is almost impossible tell between the sister species except by timing and location.

If we get them, I can't wait for a seventeen-year cicada emergence.

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