Sunday, June 19, 2016

75 Common Arkansas Insects

Most people don't seem to notice insects. If they do see one, there is first a look of revulsion, followed by a search for something to swat it with. I'm probably being optimistic, but I think if they had any idea how intricate and fascinating the life stories of insects can be, they might alter their attitude. I think anyway there are a lot of people who spend time out in nature, hikers, fishermen, gardeners, who notice things, and are at least a little bit curious about what they see. I'm contemplating writing a little booklet just for these people. If I can point out something to them that is commonly around, and is easy to recognize, and if I can tell them some little something of interest about it, maybe they will look at it a bit more favorably the next time they see it. This booklet (to be called 75 or whatever number I finally arrive at Common Arkansas Insects) will have a photograph of an insect at the top of each page, with a small paragraph about the insect beneath it. Here are some sample pages.

75 Common Arkansas Insects

American Carrion Beetle (Necrophila americana)

Don't confuse the name of this common species with that of the rare and endangered American Burying Beetle. But it is in the same lugubrious business: helping to clean up dead bodies. Its name Necrophila means 'lover of dead bodies.' When they get a whiff of a road-kill opossum or some other delectable, they head for it. They fly fast and directly, at about our eye-height, and something odd occurs. They are suitably black for their job, but note the yellow thorax with a dark patch in the center of it. This is the pattern of a bumble bee, with its fat black body and hairy yellow thorax with a dark bald spot in the center of it. When you see one of these beetles flying, you can't believe it isn't a bumble bee. I'm an experienced field biologist, and even I have to strain my eyes to see that it is actually a beetle pretending to be a bumble bee. It might make a bird hesitate to grab something out of the air if that something might have a formidable stinger.

Once it arrives at the kill it feeds on the abundant fly maggots, and lays its own eggs, and when they hatch, they begin feeding on the skin and dried bits of sinew the other scavengers can't handle.

13-Year Periodical Cicadas

Cicadas in general, found all over the world, are the large oval-shaped insects that sing and clank and zing all through the long hot days of summer. You see the empty skins of their nymphs clinging to the base of trees when you get up in the morning, but after that you only hear them, because the adults sing hidden in the tops of trees.

However one special group, the Periodical Cicadas, are easy to see just because there re so many of them. These harmless, but rather sinister looking creatures have jet black bodies, blood-red eyes, bright yellow veins on their transparent wings. Here's their bizarre story: The nymphs hatch from eggs laid in trees and burrow underground where they feed by sucking the juice from tree roots. All species of cicadas do this, and most emerge and change into adults in a year of so. But the Periodicals found in Arkansas stay underground for thirteen years, and then emerge in scattered places (each place well known to biologists) around the state. The populations are staggered so every few years some will come out somewhere. There are four species, and in May and June of 2015 all four emerged at once. If you looked up in the trees you could see them constantly flying out from among the leaves, as numerous as bees. Their high-pitched whining hissing sound could be heard, in places, for over a square mile. They had no fear or avoidance instinct. Birds and other animals could eat them all day till they were sick; there were still millions left, to mate and lay eggs for the next thirteen years. Within days the dead and dying began littering the ground. After a month they were all gone, not to appear again for several years.

An identical set of four species comes out every seventeen years, but none of these happen to occur in Arkansas. The two groups, 13- and 17-year, are found in scattered localities in the eastern United States, and nowhere else in the world.

Hanging Thief, Diogmites sp., Asilidae, Robber Flies

Unless someone points them out to you, you are likely to overlook robber flies. There are over a hundred species in Arkansas in all sizes (from 3 mm to 50 mm) and shapes (they often mimic wasps or bees, especially bumble bees). They are powerful charismatic predators, in fact each is the alpha predator in its particular ecological community. Once you get your eye in for them, you will see them sitting at the tip of a twig, or on a bare patch of ground, with an unobstructed view of the sky, and suddenly they will fly up so rapidly they seem to vanish, only to reappear at the same spot an instant later, this time carrying some insect they have just snatched out of the sky. They fly up like falcons, wrap their long spiky legs around their prey (often wasps or other dangerous creatures, even other robber flies), stab it with their beak loaded with neuro-toxins and digestive enzymes, and return to earth to suck its juices. Those like this one, in the genus Diogmites (sometimes called "hanging thieves") have the habit of getting under the foliage and hanging by their forelegs to eat their prey. You can recognize them by this behavior.

Robber flies have these features in common: widely separated eyes for good depth perception, a sharp beak, a sort of beard or mustache above the beak, which is thought to protect the eyes during encounters with dangerous prey, and long muscular spiky legs with hawk-like talons at the ends.

Hanging Fly

Here is another kind of predatory hanging fly. This one is a member of the Scorpionfly family (Panorpidae), and is much less formidable than a robber fly. It's a spindly creature looking rather like a crane fly, but has its own novel way to capture its prey. The male, pictured here, like the Hanging Thief, gets down low in the foliage and hangs by its front legs. But look at its hind legs danging below it, with their complicated spiny feet. They are like loaded mousetraps, and if a moth or other soft creature in its flight brushes against these feet they snap around it in a flash.

The Hanging Fly is not hunting on his own account. The female will not allow him to mate with her unless he presents her with a meaty gift to eat while he is doing so.

Mantises catch prey with their predatory front legs, robber flies catch prey by wrapping all six legs around it. The hanging fly is one of the very few I can think of that catch prey with their hind legs.

Braconid Wasp sp., Genus Cotesia

Sometimes something white down in the shrubbery will catch your eye. When you bend down and look, you will see a stationary caterpillar with up to a hundred tiny white cocoons clustered on its back, or sometimes in a tidy stack underneath it. It has been parasitized by a tiny (5 mm) Braconid wasp which has used its ovipositor to inject dozens of eggs inside the caterpillar's body. The wasp larvae have devoured the caterpillar from inside, eating non-vital tissues at first, so that the caterpillar could continue eating and growing, but now to feed them, not the moth or butterfly it might have become. When they were ready, they punched their way out and spun their cocoons. The caterpillar may still be alive for a while, but hasn't the energy left to make it own cocoon.

It's a common fate for caterpillars, but actually the wasps are the heroes here, the great controllers of population. Without them, and the migrating warblers and other carnivores, caterpillars would overrun the world, eat everything green, and bring down their own environment.

What do you think? Should I go on with it?