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Today is a Good Day for Cicadas!

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Today is a Good Day for Cicadas!

Okanagana rimosa specimen

Despite the slow start for our Tibicen species of cicadas, I think we are at the peak of the emergence now for O. rimosa. If you remember, I started looking for this species earlier than usual this year because in previous years I would always get a late start. With the emergence of the periodical cicadas last year on Cape Cod, I really didn't have time to seek out O. rimosa then.

By now, there should be Tibicen cicadas calling in the trees but its' unusually quiet here in Massachusetts. Not only here, but it's quiet in other places as well in the Northeast.

Doesn't matter though, because I'll keep coming back to the Montague Plains until O. rimosa is done for the season, which should be very soon now. I'll be lucky if I come back here next week and they're still calling.

More On Other Fauna at Montague

Grey Tree FrogI arrived at Montague around 9:00am in the morning and I started walking around in the pine saplings underneath the power lines when all-of-a-sudden the cicadas started calling in the low vegitation! It would seem that when its cool at night, they migrate to the lower vegitation where its warmer and when the air heats up the next morning, they slowly make their way to the larger treetops.

Its during this transitional phase when I seem to catch most of these cicadas.

While doing my rounds, I noticed a grey tree frog resting in the branch crotch of one of the pine saplings. Even though they are green, they are still referred to as the Grey Tree Frog, go figure!

Five Cicadas Caught!

O. rimosa on pine saplingI think this has been the single-most successful day catching O. rimosa here at Montague. What is especially exciting today was that I caught a female specimen by sight. Like I've stated previously, I'm getting pretty good at spotting them in the pine saplings though I still suspect that I'm completely missing some because they camouflage so well. To the right is a zoomed in image of a male specimen resting on one of these pine saplings. I noticed it because it was calling. Notice how yellow it is! More on this specimen if you read below.

In the morning I caught the one female and 3 males in the first 1/2 hour that I was there. The calling from the low vegitation was quite intense. I even startled a few causing them to fly off into the high trees. However as the day grew long, they all seemed to move into the high trees where trying to locate them by sight is extremely difficult and really not worth the effort unless they are down low.

When I catch males and females, I like to keep them separate. I don't want any schenanigans going on in the same specimen container. So that is why I like to carry several specimen jars. I put the males in one jar with some scrub oak branches and I did the same for the female.

After spending several hours at Montague, I decided to do one more quick survey and found an additional male Okanagana on another scrub pine. It wasn't calling but I managed to spot it anyway. I stuck it in the jar with the other males and brought them home.

Female Okanagana rimosa lateral view

Female Okanagana Ovipositing.

Female OkanaganaI usually like to photograph all my specimens when I get home. Since catching the female is a rare occasion, I started with that specimen first. Females of this species have a tendancy to run a little larger than the males (at least from what I can see) and of course their anatomy is different from that of their male counterparts. For one thing, they lack the organs necessary to sing and they have something that males don't and that is an ovpositor. Despite this you can usually tell a male from a female based on the shape of the abdomen. In male Okanagana specimens the Uncus is always exposed causing a distinct change in shape of the abdomen dorsaly to that females (See Davis).

Female Okangana ovipositorThe female's ovipositor is a thing of ingenious evolutionary design. When in use, the very tip is shaped like an "arrowhead" and is serrated. They use this to make a series of small slits in branches of plants where they deposit their eggs. When the ovipositor is not in use, it rests medially along the abdomen nestled between a specially adapted elongated set of sternites. (click upper-right thumbnail for a closer look). You may find that the length of the ovipositor may differ among cicada species but the special adapation as to how it rests when not in use and the specialized tip for making slits in branches is pretty much the same among all species.

Okanagana egg slitsWhen I took the female out for photographing I did notice a series of three slits had been made in the oak branch that I added to the jar so that it could feed. I have often wondered since these Okanagana prefer areas with pitch pine trees, if the females actually oviposited in them. I have a hard time rationalizing the very thick and viscous sap that oozes from these pine trees and have thought that perhaps these trees may not be a good medium for their eggs. Cicada egg slitsAfter all, when the first instar nymphs hatch, wouldn't they get stuck in all that reson and be unable to make it to the ground for their long juvenile development cycle? Finding these egg slits in this oak branch really doesn't prove all that much, unless I can find evidence of egg slits in other scrub oak trees that I find at Montague. Maybe they really don't have a plant preference and will oviposit in just about anything. Who knows? I will put the female in a maple tree at my house to see if any more ovipositing occurs.

Okanagana eggsOkanagana eggs closeupThe female only made three slits in the branch. This is probably because the branch was too short and was only approximately a 16th of an inch in diameter. When I took the branch apart to get at the eggs (yeah, you knew I had to do it didn't you?), I discovered approximately 20 eggs distributed among the three slits. There is a possibility that I may have missed some of the eggs because they are very small (less than 2 millimeters long) and are very slim. Click the images and especially the one below to get a sense of exactly how big these eggs are. I used a ruler in millimeters to give you a sense of scale.

An Unusual Morphology Among the Males.

Yellow Male O. rimosa dorsal viewTypical orange male O. rimosaYou know, you can take this with a grain of salt but I noticed something with these male Okanagana that I collected today. One among them has yellow markings as opposed to the standard orange-red markings typical of this species. Reading several W.T. Davis papers on the subject of color variability in this species Davis mentions that given their wide range in distribution that color variability as well as physical characteristics may happen. In fact, Davis describes a variety of O. rimosa known as var. ohioensis. These apparently are more robust than regular rimosa and even exhibit "hairy" characteristics.

Yellow abdomen male O. rimsosusOrange abdomen Male O. rimosaAt first, I thought that this particular male may be a newly emerged teneral. When I got home and looked at the specimens from my previous trips to Montague that were still alive, I found that one of these was yellow as well. I thought perhaps that these may be O. canadensis which is a yellow Okanagana also found here in the Northeast but their calls are vastly different from O. rimosa and these males that I caught have virtually the same call as their orange counterparts. Also I believe that O. rimosa and O. canadensis are not sympatric (living in the same place). But, like I said, I need to find O. canadensis because I don't have any voucher specimens.

The four thumbnails above are positioned with the yellow variety on the left. Compare these to the standard orange-red variety thumbnails to the right. You can click on them to view larger versions of each.

Another physical characteristic that I have noticed with this yellow variety is that the two that I have tend to run smaller, being a lot "leaner" in the body than their orange counterparts. The two specimens that I have lived longer in captivity as well. I will be taking detailed measurements of these specimens as soon as I get them all pinned and labeled. Maybe I will notice something else when all's said-and-done.

Date Posted: 2009-07-11 Comments: (0) Show CommentsHide Comments


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