Please Don’t Squash That Spider
Almost every day recently I have blundered into spiderwebs that drape the garden, stretching from branch to twig to leaf everywhere I (don’t) look. It must be August, the month of spiders. Each summer, the air is filled with what looks like cottonwood down but is really a host of infant spiders, riding the wind on silken parachutes. Thanks to E.B. White’s charming story, Charlotte’s Web, the sight cheers many a gardener’s heart. Charlotte taught us to appreciate the delicate beauty of spider webs and helped us see spiders as nature’s bug catchers.
Observant gardeners may identify dozens of these hungry helpers, of which some 30,000 species are found worldwide. In our own gardens, we are most apt to notice plump orb spiders sitting by intricate webs. Many have ornate back patterns that offer protective coloration, attract mates, and even inspire artwork (imagine a needlepoint pillow worked like a dappled spider!). In bed and borders, hunting spiders catch aphids and mosquitoes, while crab spiders wait patiently for tiny wasps to visit flowers, cleverly altering their body color to match the host blossom.
Aphids and Flies and Cockroaches and Earwigs…
Although spiders are fascinating to watch, their big appetite for insects is what endears them to the gardener. Spiders are not insects but insect eaters. Eight-legged arachnids, from garden spiders to their distant kin, the horseshoe crabs, honor the mythological Arachne who won a weaving contest with Athena herself. Though many spider species are hunters, well over half are web spinning trappers. Prolific past counting, spiders consume an estimated five to ten times as many insects as birds, helping gardeners and farmers all over the world to keep plant pests at bay.
Weaving A Web
Most of us first notice garden spiders when their webs spangle the garden like great, lacy doilies. The bullseye webs of orb spiders are the most obvious, but a little searching will reveal webs like funnels, sheets, and hammocks as well as the rag-bag webs called “cobs”. Some spiders create new webs each day, while others make a single web that endures a lifetime. Many species keep their webs immaculate, instantly repairing the least flaw, while a few let their webs degrade into tatters before replacing them.
Spider silk starts as liquid protein, squirting from tiny organs called spinnerets. Instantly, it hardens into thread so durable that scientists spent years attempting to reproduce it. Today, synthetic spider silk is used by NASA in space missions and in hospitals for micro-surgical applications.
Arachne’s Finest
Spider silk’s strength and elasticity change depending on its production; the faster silk is spun, the tougher it is. In one test, a single spider produced 150 yards of the strongest dragline silk in just over an hour. Finer than human hair, each strand is actually a hollow, twisting tube; the spiraling turns provide elasticity and the inner tube holds a reserve of sticky capturing fluid.
Up to three times stronger than steel, spider silk can stretch twice its original length before breaking. Moisture won’t rot it. Heat and cold can’t change it. Spiders, however, recycle their miracle fiber effortlessly, consuming old webs and converting the stored protein into new ones in under an hour.
Spinning On The Wind
Since spinnerets lack muscle fibers, spiders use gravity and wind to alter silk production speed for each kind of thread. First, they squat over the primary web attachment point, eject a dab of silk, then release themselves to the wind. These sturdy support threads (and hunting spiders’ draglines) are spun the fastest, while more supple inner web segments are built inch by inch. Finest of all are the capture threads used to bind insect prey. Certain spiders fill the inner web with a series of rickrack-like threads (stabilimentum) that reflect light, perhaps to warn web-breaking birds away.
In the beautiful orb spider webs, the main dragline anchors an irregular outline which is filled in with a series of radiating spokes. These are woven together with a wheeling spiral of silk, smooth on the outside and sticky at the center. When bugs and small moths blunder into the web, they stick there until their thrashing alerts the waiting spider, who rushes in for the capture and the kill.
Next time you spot a spider, think of all the bugs he or she has eaten and just say thank you!