ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Sunday, September 29, 1996 TAG: 9609300011
SECTION: CURRENT PAGE: NRV-2 EDITION: NEW RIVER VALLEY
COLUMN: Dispatches From Rye Hollow
SOURCE: STEVE KARK
I teach writing at Virginia Tech. When I ask my students to write about nature, they usually approach it from perspectives that are either black or white. Nature is either a terrible force, as in the case of hurricanes or blizzards, or they see it as something that inspires or nurtures.
They write about beautiful sunsets or stimulating hikes. A few might suggest that nature can be both a good and a bad thing, but there are no shades of gray. Nature, it seems, is either a bully or a saint, or some demented combination of the two.
I encourage them to explore the natural world and to research what they find so that they might come to a deeper understanding of themselves and their world. But this sounds too much like homework for many.
Still, I'd like to teach them that sometimes even the most insignificant natural event can be fraught with hidden meaning, that the world is more complex and mysterious than they might imagine.
For instance, I might show them what I found at the edge of our garden a while back: a bug ensnared in a spider web.
That bugs fall victim to spiders is certainly nothing new; it happens every day. Factor in a little curiosity and a handy field guide, though, and it could make all the difference in what you see.
There is something unsettling about a caddis fly in a spider's web.
Not that I have a problem with spiders. As far as I'm concerned, they're welcome to as many flies as they can catch in their sticky little webs. It's just that I have a special attachment to this particular kind of fly, this caddis fly.
You see, like spiders, many caddis flies are web builders too. To be more precise, the larval versions of some caddis flies share this particular food-gathering strategy with spiders.
But, unlike spiders, the caddis fly larvae build their webs underwater. And they're very good at it indeed, even going as far as to build them inside little tubes so they might filter out the tiny bits of waterborne, organic debris that is their food supply.
More than this, these tubes are a whole lot more than your everyday run-of-the-mill insect house. Each one is a marvel to behold.
I've found some in the New River near McCoy Falls that were no more than an inch long and made entirely out of bits of sand. Under a magnifying glass, one can easily see that each tiny grain has been cemented into place with a skill that seems every bit as precise as the work of the finest stonemason.
The ones I like best, though, are constructed of minuscule bits of twig. These are fitted together to create tubes that look for all the world like little, elongated log cabins.
And, if that weren't enough, it turns out that the little bugs are competent engineers as well. According to Virginia Tech biology professor Fred Benfield, the larvae of one genus of caddis fly, Macronema, actually orient the tube so that it faces upstream. By doing so, this tiny bug is able to regulate not only the flow of water through the tube but the resulting food supply as well.
The larvae live this way underwater until they pupate and become adult caddis flies, at which point they float to the surface, emerge and become airborne insects.
This is where life really gets rough for caddis flies. Although they spend up to a year underwater, when they emerge to fly off and reproduce, they live no more than a month and rarely eat anything.
Returning to the caddis fly captured in the web at the edge of our garden, how ironic that a bug that spends so long feeding from a web should become a victim in another creature's web.
And if there is a design in nature, what sort of malicious intent must it be that rewards industry and perseverance with such an undeserved fate?
Maybe I should hold off telling my students about the caddis fly and the spider. They're still young and impressionable. Perhaps it's not the sort of thing they'd wish to hear, a lesson with too many shades of gray.
Besides, if they're like the rest of us, they'll pick it up sooner or later, anyway.
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