November 7, 2012

BACKYARD NATURALIST: The beauty of orb spider webs returned this year

Kennebec Journal Staff

In the willow-herb, bedstraw and birchling brush this fall, the argiopes and all their relatives returned.

Staff photo by Andy Molloy Dana Wilde

click image to enlarge

A black and yellow garden spider (Argiope aurantia) wraps its prey in the Unity park one late summer afternoon.

Photo by Dana Wilde

Two Aprils ago they were all but wiped out when heavy deep snow came late and their eggs hatched out too early. That summer and fall there was hardly a silken guy wire to be seen between the timothy tops and goldenrods, let alone any orb webs with a view of bug-filled airspace.

That was a bad year for spiders in the Unity park.

But better for the dragonflies, bees and lichen moths, of course, who in the normal insect routines patrol the brush at their peril. It's usually a veritable house of horrors down there for them, and for people whose imaginations run to fright at the sight of small bristly octo-legged beasts peering out from parallel webiverses.

But this year the orb webs were back, and the imaginings that go with them. Gorgeous, symmetrical silk spirals hung discreetly between aster leaves and grass blades, some with heavy zigzag squiggles at the center called stabilimentums, where the black and yellow (Argiope aurantia) and banded (Argiope trifasciata) garden spiders wait noiselessly and patiently for victims. Other webs are inhabited by smaller, mottled orange and brown cousins (that may be Araneus nordmanni species, but who knows?) keeping watch tucked up in a corner fastened to sedge stalks.

These webs are spun with startling precision and -- not to anthropomorphize unduly -- care, it seems. Orb weavers (as opposed to sheet web, funnel web or cobweb weavers) set up the construction site by trailing a strand of silk from some prominent spot, like a timothy tip, into the breeze which catches it and tacks it to a wild-madder leaf or a fence post or another blade of grass. The spider then hustles back and forth paying out silk along this bridge. When it's sturdy enough, the spider ties on another line, drops down and secures it on a stalk below. This is the first frame.

Next the spider constructs radial spokes and two sets of spirals -- one a scaffolding that will be taken down at the end of the construction project, the other the permanent structure that will snare flies, mosquitoes, butterflies and whoever else wanders in for the day's meals. A black and yellow garden spider takes about a half-hour to an hour to complete the engineering and construction of an orb web 1 to 2 feet in diameter.

To a backyard naturalist like me, who knows only what he sees and the scientific facts that can be looked up in books (or Google), there is more in these webs than meets the eye. No one knows, for example, what the purpose of the stabilimentum is. It is apparently not necessary to the structural integrity of the web. Is it a lure for dim-sighted fliers? Or a warning to swooping birds? Or is it, as some arachnologists have suggested, a decoration? After all, what is the practical point of the awesome symmetry of the web in the first place? Tangled-up cobwebs do just as well. Yet the young spiders of some species are very meticulous with the balance of the web, strand for strand, but take less care as they grow older.

That year the spiders got wiped out by a harsh New England April, the park lost some of its imaginative balance for me. I missed the webs and the little minds behind the fierce but (in New England, at least) harmless-to-humans faces that made them. There's some shared view of the world there, it seems. There were no webs, as it were, to cast my own webs over.

This fall they've been back on their usual cycles. The eggs are tucked away now to overwinter, and they're readying in the fall chill to succumb to the snows of winter bearing down into New England.

Dana Wilde lives in Troy. His writings on fall, winter, spring and summer in Maine are collected in "The Other End of the Driveway," available from Booklocker.com.

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