Monday, April 2, 2012

Beautiful Polistes and Ichneumons

The advantage of being obsessed by insects is that you can scarcely go outside the house without seeing some new creature or some new bit of behavior you have never seen before. There is so much diversity (and so little time) you can't possibly exhaust it.

Here are a few things we have seen recently, just in our garden.

To begin with, a few weeks ago the holly hedge in our front yard was blooming, attracting numbers of bees, flower flies, and, particularly, the big Polistes paper wasps, the ones that hang their pizza-shaped nests under your eaves (if you allow them to). I confess I haven't paid a lot of attention to this group of insects, so when I started photographing them at the holly, I was surprised we had such a variety of species. In fact I could do the first six letters of the alphabet with their Latin names, and still not be done. Here they are:

Polistes annularis

Polistes bellicosus

Polistes carolinus

Polistes dorsalis

Polistes exclamans

Polistes fuscatus

And there's still one more, Polistes metricus

P. metricus, exclamans, and carolinus nest around our house every year. Exclamans seem to be nervous, but not aggressive, and I've never been attacked by one. Metricus are pretty placid and I've only a few times been stung by them, usually my fault. But carolinus, the big red jobs: They are very aggressive, and I can't count the times I have been stung by them. The first time was about thirty-five years ago, when we first moved here. I was walking through a field and inadvertently came near a nest in the top of a bush. One flew out and stung me on the hand, and the next day the skin on that side of my hand peeled off as if I had had a severe sunburn. After that the stings have never bothered me very much (I wonder if you acquire a sort of immunity), and so I tolerated them around the house. But then Cheryl was stung in the eye by one, and her cornea swelled up, very frightening to see, and I took her to emergency. Since then we have been on a war footing. We practice ahimsa, reverence for life, but if we are attacked, all bets are off. The red carolinus get under the eaves of our house and nest inside the walls, and it is impossible to stop them completely.

So here's how it works. At first when they are building up their numbers, they are very quiet and sneak in and out, and are no problem. But about mid summer, when they have built up to about 150 members (this will be in each of two or three nests), then they start to get obstreperous, and I have to take action. I go out in front of the house where I can see the openings they use, and sit in a folding chair in the early evening, with a long-handled net in one hand and a glass of wine in the other. When I see one heading in for the evening, I leap up and try to net him before he makes it into the entrance. That's my adrenalin rush. Then I try to isolate him in one section of the net without getting stung (that's my second rush) then I smack him with my stick. It's my annual courage test. For a while they think of me as a predator, and get sneakier and faster with their entrances. Then they get mad. They start gathering at the mouth of the nest and I shake my net at them to enrage them, I poke the net at them until they charge me, then I frantically whip the net round and round trying to get them before they get me, and hoping Cheryl isn't watching my gyrations through the window (she has a terrible way of taking movies of these things). From time to time my nerve breaks and I run clear out to the road. I can handle the frontal assaults, but they have a deadly one where they shoot in from behind me at top speed, and somehow sting me in the back of the head without even a pause in their flight. Anyway, I try to catch twenty every night, and after five nights I have taken them down far enough they are no further trouble, at least for another month or so.

But that's way ahead of the story. Right now all the Polistes Wasps are single queens sitting on a nest of three or four cells, trying to produce some workers as quickly as possible.

There are other hymenopterans of interest in the yard right now. Last year I took some  6-foot-long cypress sticks and tied them together on the top to make a sort of tripod for morning glories. Cheryl and I were standing by it the other day when a big red ichneumon wasp flew up and landed on one of the sticks.

We looked it up in BugGuide and believe it is Labena grallator, or something close, and it had come to our sticks because they were infested with wood-boring beetle larvae, which some of these big ichneumons specialize in. They listen with their antennae, and when they hear the movement of a grub, they saw their way down to it with their immensely long ovipositors, and deposit an egg on it. I was especially interested in the color pattern of this one. A lot of mimicry goes on in insects, a harmless species putting on the appearance of an insect known for its painful sting or bite, or its bad taste, and that way birds and lizards might hesitate to pick up the harmless one too. When this one first arrived, I thought it was a Polistes Wasp (and I wouldn't have picked it up). Here is how it fooled me.

The Polistes Wasps are a highly advanced group of social insects. Among other high-tech changes they have made, they have converted their long ovipositors into painful stingers hidden inside the tip of their abdomen, and then, having these dangerous defense weapons, they have painted themselves in black and red and yellow warning colors, colors that mean you'd better not touch me. Birds and lizards and people know these colors well. The Ichneumons are a primitive group of wasps, with no stings, instead still using their ovipositors to deliver eggs. A great long ovipositor therefore gives away the fact that they are stingless. So note first of all in the picture above that this ichneumon's ovipositor is yellow on the basal half, then black. So from many angles it doesn't look like a long ovipositor. The yellow part just looks like one of its yellow legs, the black part disappears in shadow. Now note the colors: They are the black and yellow and red warning colors of a Polistes. Look at the next picture, of P. dorsalis: Not a bad match at all.

Here is this ichneumon in action, drilling down to the beetle grubs. The yellow part is the sheath that carries the ovipositor. The black thing is the ovipositor itself. It looks a lot like a well-drilling rig.

At the same time, another beautiful ichneumon, also a wood-boring beetle specialist, Dolichomitus irritator, was busy on another part of the tripod.

From time to time I might be able to write more about ichneumons. After all, there are roughly 4000 species north of Mexico.


  1. Wonderful post about wasps and ichys, Norman! Keep up the good work, Jeff.

  2. Wonderful post about wasps and ichys, Norman! Keep up the good work, Jeff.