Friday, May 30, 2014

Geolycosa and Geometer

Back in 2011 we were on the prairie portion of the Jonesboro Nature Center when Cheryl discovered a Geolycosa missouriensis, and took this very nice photo of it:

Here it looks more like a gopher or some other small burrowing animal. In fact it is a handsome and very interesting spider. Geolycosa, 'earth wolf,' is the genus name for the Burrowing Wolf Spiders. We were especially delighted with it because Peggy Dorris in the 60's and 70's published, in several papers, her wide-ranging survey of the spiders of Arkansas, and she had not found this species, nor any other burrowing wolf spiders, among the 435 she recorded. So, in addition to being handsome, it was rather uncommon, not very well known, and quite interesting in its behavior. But we were concentrating on grasshoppers that year, and didn't follow up on it.

This year, the beginning of our second year on spiders, we went back, and checked out the prairie with burrowing wolf spiders in mind. Here is what we discovered. We had often in the past noted, when we were in this sort of terrain (namely a rather flat area with sandy soil and lots of bare ground), that there were round holes in the ground often with bright orange fresh sand from recent digging scattered around them. There were also lots of solitary hunting wasps around, and we assumed these were wasp holes, dug to deposit an egg in along with a paralyzed caterpillar or whatever host animal they specialized in. This year we examined these holes more critically. If you look carefully at the picture above you will see that the sand right around the mouth of the spider burrow has been tied together with spider silk. Well, we noticed that was true of most of these holes we were examining, holes that in size went from a diameter too small to stick a pencil in, to one that would require a quarter to cover it. Some even had dried plant material sewn into the sand, to make a little turret around the entrance.

When we saw these holes in the past, they were always empty, and so were they this day. But I decided to sit down and wait quietly by one, and see what happened. I'm not a particularly patient person, but I thought I would give it a full minute, counting out sixty seconds, one one-thousand, two one-thousand....

And as you can see in the picture above, before I reached sixty, legs began appearing down inside the tube and slowly rising to the surface. I very quietly raised my camera and aimed it at the top of the hole.

I made the tiniest movement, and it disappeared in a flash.

You see the pattern of this spider: a black body with gray hairs over the top, two-tone black and orange legs, and the chelicerae, the sort of mustache in front of the face, covered with yellow hairs.

I've described the habitat. Sandy soil, because sand is easy to dig in. The land mainly flat, but with some areas raised a few feet in elevation from the rest, or places with gradual hillsides, and those were the places where we found all the holes (often half a dozen in view at a time). Obviously a design to avoid flooding in heavy rains. The holes always appeared empty to us because the spiders are so sensitive to the least vibration in the ground, and have such sharp eyesight, that before we got close enough to see into the hole, they had already dived to the bottom. The one-minute rule, however, appeared to be standard for all of them.

To the north of Jonesboro in Greene County is Scatter Creek WMA. There is an area there of abandoned quarries which had all the proper ingredients, and when we checked it, it was similarly full of holes in appropriate locations. Here are pictures of one spider I waited by, keeping very still so that I didn't disturb it before it was fully out.

After the sixty-second count it was up just below the top. There was a cautious wait there, and then it moved up so it could see over the top. Another wait. When it felt completely secure, it moved its second pair of legs straight out in front, and that was its final comfortable position for surveying the landscape in front of it for prey. I didn't catch it in the act myself, but Cheryl was watching another spider on the side of a hill when she saw a small beetle trundling down the slope towards it. When it was four or five inches away the spider noticeably tensed, the beetle suddenly froze, then the spider rushed out and grabbed it and carried it back down into the burrow.

If you are a follower of this blog you might remember that I showed some pictures of another large wolf spider, Hogna carolinensis, which had a burrow with a similar turret, but otherwise their behavior is different. Many of the Hognas make burrows that they conceal themselves in during the day, then at night they come out and wander around looking for prey. Geolycosa comes out by day, sitting at the top of its burrow waiting for prey. I don't know this for sure, but I suspect they go back down into their burrows to rest during the night. There are other parts of their behavior I will try to learn more about this summer while I have these two big populations to monitor. My understanding is that at this time of year both males and females live in their burrows, but in late summer and fall, the fully grown males leave their burrows and go looking for females.

Now, on a different subject, look at this picture and tell me what you see.

Geometers make up a large family of moths. Geo, 'earth,' meter, 'measurer.' Its the family whose caterpillars are the familiar "inchworms," or "measuring worms," that progress by arching up their long bodies and sending the front of their body as far forward as it will go, then arching up their body again to pull the back half up to catch up with the front. But some of the caterpillars in the geometer group have a much more remarkable ability. They can hold their long bodies absolutely straight, and keep them stiff and rigid for hours at a time. To go along with this ability, often their markings precisely mimic the wood and bark and complicated joints of twigs. Birds feeding on caterpillars use the shape of a caterpillar as a search image, and caterpillars go to extraordinary lengths to break up that pattern and look instead like something inedible.

Last week we found (droppings underneath it provided a clue) what must be the world champion in this type is dissimulation. The caterpillar (that's what you were looking at) is on the trunk of a small bald cypress in our front yard. Several new cypress shoots are growing on the trunk at just that angle, in just that color and texture. Since we discovered it, we have been keeping an eye on it, and it holds that position all day long. It's been doing it for at least the week we have been watching it (a bird with a good memory might note that it is in a slightly different place each day.) Last night we finally remembered to go out and check on it at night.

Sure enough, that was when the caterpillar (we still are unsure of its identity) climbed up into the cypress tree foliage to feed.

Sunday, May 11, 2014

The last days of the bird feeder

When winter closed in last year, and there were fewer and fewer insects and spiders around, we gave in to the inevitable and set up bird feeders. We  hung up a tube feeder of sunflowers seeds, a white sock of niger seeds, hung up some suet cages and scattered finch seeds and sunflower seeds on the ground outside our dining room window, and down our second, largely unused, driveway outside the kitchen window.

Of course you argue that you are saving the birds from starving during the bleak cold winter, but the truth is in most winters the birds can shift for themselves as they did for the thousands of years before our arrival. No, the feeders are set up so you have the pleasure of drawing the birds to your yard so you can watch them from close up. And you especially hope the gabble of feeding birds will be a magnet for any rarities that happen to be in the neighborhood.

Well, we did have all those pleasures this winter, more so than usual. You see, I used to be a keen bird watcher, but over the last fifteen or so years I have become enamored of insects, and more recently of spiders, and what I like most of all is recording them on camera, especially their behavior. I'm not primarily a "photographer," which is to say, I am not interested in the technical aspects of my equipment, nor do I know much about it. The camera is just a means to an end. I have an SLR with a 100mm Macro lens which I usually use with extension tubes so I can take pictures from only a few inches away. Cheryl has a very small camera which she carries in her pocket, with which she can focus on objects from less than an inch away. I can get large reasonably sharp images of shyer creatures from a few inches back; she can get up tight on extremely small subjects, especially ones in awkward corners my bigger camera can't get into.

Anyway, it happened that all the guys decided it was better to photograph insects from a distance with a 300mm telephoto lens, usually mounted on a tripod for steadiness. This produced perfect pictures of, for instance, dragonflies. Well, I wanted to be one of the guys, so I got one of these big lenses, and while it produced some nice pictures of dragonflies, I found it cumbersome and not very useful for pictures of smaller, more active, insects. I stuck the lens in a drawer and tried to forget how much it had cost.

But this winter when the birds started coming to our feeder, one day I attached the big lens to my camera, idly pointed it out the window and snapped a picture of a bird. To my amazement, even hand-held and through double panes it produced a sharp picture, even showing those neat barbs in all the feathers that are the vogue with professional bird photographers these days.

I was quickly hooked, and spent a lot of otherwise boring insectless winter days taking pictures of birds. The long-lens more than paid for itself with the fun I had. At first I couldn't believe how good my pictures were. Then after about a month I looked back at them, and realized they weren't all that good, and the new ones I was taking were much better. I went through this cycle periodically over the winter, at first thinking I was taking prize-winners, then later realizing they weren't even keepers compared to the pictures I was THEN taking. What it meant was, I was learning a new skill.

The other part of the fun was, we were drawing in some special birds. Rusty Blackbirds, for instance are a species of concern, their numbers going down rapidly. We are asked to keep track of them here in the south where they spend the winter. Well, that was easy for us: in the coldest part of the winter a small flock moved in with us and stayed. They are a kind of blackbird, all black in their nesting territory on wetlands in the upper mid-west, but here in their winter plumage they are every possible pattern of rustiness.

And we got another nice bird, an American Tree Sparrow. This is a rather scarce pretty little sparrow that normally we would see once or twice during the winter, just a glimpse of it out in the country mixed in with a flock of commoner sparrows. But this bird appeared at our feeder and stayed all winter. We got to know it, something we had never been able to do with all our brief glimpses in the past.

But just as in summer the days rushed on to autumn, the days shortening and darkening, the insects reaching their maximum numbers, then quickly declining, so suddenly (now that we were having fun) just before we left on our trip to Arizona in April we noticed the big flock of American Goldfinches that spent the winter at our feeder were changing. Goldfinches often seem to disappear for the winter. They don't. They just put on their dull gray winter plumage and you no longer recognize them. But now our big gray flock was coming out in yellow spots.

By the time we got back from Arizona their transformation into summer plumage was virtually complete.

Here was hard irrefutable evidence that winter was over, and instead of cheering I felt a sense of regret.

But at just that moment, we had the highlight of the year, a real rarity. The White-winged Dove is a western bird that is beginning to invade Arkansas from the west, but many good Arkansas birders still have never seen one in the state. Here we are in the eastern side of the state, and one morning when we went outside, we were quite sure we could hear one calling in the woods across the road. Sure enough, the next morning there it was at our feeder. It looks rather like our common Mourning Dove, but has a big white patch in the wing that you can see even when the wing is closed.

He stayed around for a few days, eating our seeds, singing from our trees, cruising some of the female Mourning Doves till their husbands expressed disapproval. Then he moved on.

The time for the bird feeder was over. I was nearly out of birdseed and wasn't going to buy any more. What we suspected was a raccoon had come in the night and stolen our suet feeders. Most of the birds had deserted us and headed north anyway. And then a funny thing happened: Mammals began to take over.

I have already told you about the voles that came from underground to share the seeds with the birds, and the Gray Squirrels had been vacuuming up stuff we put out all winter. Now a Hispid Cotton Rat appeared (hispid refers to his rough shaggy fur) and began feeding on the leftovers.

Then, only slightly bigger, a tiny smooth baby rabbit appeared, using its nose to find buried seeds the birds had missed.

Then a big gangling cottontail that looked halfway to being a jack rabbit.

The final finisher came minutes before darkness (I took this picture at 3200 ISO), looking off into space while using his deft hands to scrape up hidden seeds under the mud, and using the puddle from a recent rain to wash them in.

So that's it.  Bring on the bugs and spiders!