Monday, July 21, 2014

Home and away, Part One

Our yard has reached that degree of perfection that essentially come spring we don't plant anything, we don't weed anything, we just step back and let it all come up of its own accord, and each year it comes up taller and thicker. Our favorite habitat in the world is the tropical rain forest, and this is as close as we can come in our temperate clime. Oh, it might be a bit overgrown, in places there are thickets we no longer have access to, there is so much aquatic vegetation in our pond we can no longer see the water surface. But the only regret I might sometimes have is that when we were first here I kept planting more and more trees, tiny saplings that have now grown into big trees, and it is getting as shady as the woods across the road from us (which is itself getting overgrown), and that might reduce some biodiversity, but there is still plenty here to keep us occupied.

For example last year I found an amazing 104 species of spiders here in our yard (and house), and, when I used to keep track, we regularly found over 60 species of butterfly in the yard every year (though I doubt we still could find that many as the yard becomes more enclosed in the woods, and also as butterflies continue, as I suspect they are, their steep decline generally).

There is still lots of butterfly activity. The brash and bright colored Zabulon Skippers have taken over the pond and chase off everyone (including me) who comes by.

All in the hopes of winning the  heart of the quiet and gentle female of the species.

The handsome Black Swallowtails are laying their eggs on our bronze fennel, and these are hatching out and growing into big, striking caterpillars.

Horace's Duskywing (some classicist named a bunch of duskywings: Juvenal's and Propertius are others) are courting and mating.

A pretty little Sleepy Orange appeared in our garden, nectared on our flowers, then laid its eggs on our senna plants. The nearly microscopic eggs have now hatched and the rather ordinary looking caterpillars (the later instars are more attractive) are growing rapidly.

A Buckeye butterfly has just today eclosed from its chrysalis.

When it was ready, it flew off and we thought it was gone, but then Cheryl found it in a far corner of the yard and took this beautiful picture of what might be our most beautiful butterfly.

Of course there are a lot of interesting moths and moth caterpillars as well. We especially like this one, a Double-toothed Prominent. The back of the caterpillar mimics the double-toothed leaves of the elm trees on which it feeds. As it eats one leaf from the edge in towards the midrib, it fools birds into thinking it is merely the other half of the leaf.

There is a whole ecosystem beyond the lepidoptera, including a number of predators. For instance this very big Laphria grossa, a bumblebee-mimicking robber fly, here with its decorative prey (robber flies have a nice design sense), a flower scarab.

On a smaller scale, this tiny assassin bug has caught a Cuckoo Wasp. The wasp has such strong armor plating an entomologist would have a hard time sticking an insect pin into it, and yet this fragile bug has managed to stab it with its beak.

That was an assassin bug with prey. Here is an assassin bug as prey. The spider is the handsome Paraphidippus aurantius, the Emerald Jumper.

The Cuckoo Wasp was prey, but here are some wasps in their more usual role as predator. I read in my Eric Eaton Kaufman Field Guide to Insects that there are 280 species of wasps in the subfamily Eumeninae, the Mason Wasps and Potter Wasps. These are all very similar appearing black and white or black and yellow wasps that make use of abandoned nests of mud daubers or carpenter bees or other cavities for their own nests. They fill these cavities with paralyzed caterpillars and then lay an egg in them. One of these wasps right now is using a space where canvas is folded over the top of one of the chairs on our front porch. It seems like every time we come out it is dragging another hapless caterpillar up the chair leg.

Some members of this group, those in the genus Eumenes, are called potter wasps, because they make their own nests, exquisitely shaped clay pots using the coil method of construction that they invented millions of years before we did.

When I started this post I just called it "Home and Away," planning to contrast this account of what we are seeing around our home right now with what we see going out for the day to one of our favorite places. But now I see that I could go rambling on about what we are seeing around the house almost endlessly. So I'm going to stop here, and in the next post (Part Two) I'll do "Away."

Well, I'll mention one more thing. What I have done for the last couple of nights is to go out at late twilight and try to take pictures of the fireflies just at the instant they are flashing. What I do is run over to where I see flashing, look in its direction through the view finder focusing frantically back and forth till I catch the tiny flying black dot in the near darkness, follow it trying to keep focused on it, then try to catch it in mid flash. What I usually end up with after several tries is one picture where the firefly is in quite good focus, but not flashing, and one that is flashing, but out of focus. If I knew something about photo-shopping, maybe I could meld them together. Anyway, try it. It's fun.

Sunday, July 6, 2014

The Black-and-yellow Garden Spider, Argiope aurantia

If you have an overgrown garden you have benignly neglected for many years, if you never use pesticides, if you have fervently absorbed Oliver Rackham's (in his great book, The Illustrated History of the [English] Countryside) sternest and most important dictum about having a garden, "Learn to detest neatness," then by mid summer you are bound to have at least a few Argiopes behind bushes or in ignored corners, those enormous golden garden spiders sitting in the center of their big webs with the zig-zag stabilimentum going down through the middle. I have been observing them for years, always learning new things.

Now, these big brightly colored spiders seem to appear out of nowhere. They aren't there one day, and the next day suddenly there they are. Well, if you start really looking you find they are there all the time, only in smaller, less recognizable instars. It might take you a couple of seasons, but eventually you push them back to the beginning. Maybe the first day of summer, June 20th, is a good day to start looking out for them.

What you'll see first, down low in thick vegetation, is a white thing about the size of a postage stamp.

Take a close-up with your digital camera and you will see a tiny spider. The only similarity it has with a full-grown Argiope is that it is sitting head down with two pairs of legs forward and two back. The stabilimentum, instead of going up and down in a zig zag, is a tightly woven squarish circle just the size to hold the spider's body and legs.

Nobody knows precisely the purpose of a stabilimentum, though recently it has been shown that they reflect ultra-violet light, and thus might act as an attractant to insects. But this baby stabilimentum has its own neat little function. Now you see the spider, but at the least disturbance, the spider vanishes quicker than you can see.

After another instar the silk mat is a bit larger, to hold a spider that is beginning to look more like an Argiope.

By another instar the spider is still too small to be noticed unless you are deliberately looking for it, but now the baby mat is beginning to extend into the up-and-down zig zag of the adult.

It can still perform its disappearing act.

With the next instar it has its adult stabilimentum.

And then, its adult color and pattern, though its abdomen still has its long narrow shape, not yet its rounded adult shape.

Interestingly, I saw all these different stages on the same day last week. The progress is very irregular. I think the tiniest spider must set up shop, and just wait for insects to come. If they don't, it stays the same size, if it makes a couple of lucky catches, it molts up to the next stage, and the more insects it catches, the quicker it moves from stage to stage, while the unlucky spider with a poor spot sits waiting. Even quite late in the summer I have seen that first postage stamp size, while the huge fat adult females are laying egg nest after egg nest.

At any rate, with decent luck, at last the spider reaches the penultimate molt, and males, battling one another, begin hanging around the edges of the web, to be the first one there when she sheds into full adulthood ready to mate. Here is that next to last molt, and she still has her girlish waistline, before it starts ballooning out with eggs.

If you want to follow the story, I've done an album of the life history of Argiope aurantia which includes a life history of Argyrodes, the tiny spiders that live parasitically in Argiope's web.

Click here