Wild Side: Spiders may frighten us, but they are also fascinating

Wild Side: Spiders may frighten us, but they are also fascinating

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An orchard spider mans a web that it spun in the author's outdoor shower. The silk that spiders deploy is remarkably strong and pliable. — Photo by Matt Pelikan

It’s hard to think of a more maligned group of wildlife than the spiders. Whether our aversion to these eight-legged critters is innate or learned (or a combination), it seems like nearly everyone shares it to a degree. It’s not a wholly unwarranted fear, since there are a few highly venomous spiders. But the vast majority of these interesting arthropods are harmless, indeed beneficial, to humans, and spiders play vital roles in maintaining ecological balance.

While some species have been studied in detail in our region, and some Vineyard properties have been well surveyed for spiders, I’m unaware of any comprehensive study of the Island’s eight-leggers. But it is clear that hundreds of spider species are out there, industriously preying on insects and other spiders.

I’m sorry to say I share, to a degree, the typical aversion to spiders. Though I realize the fear is irrational, it takes a bit of mental effort for me to hold a spider. And perhaps that’s why I’ve never studied them. But I watch them with interest, and I’m constantly amazed by the abundance and variety of spiders here. As with other wildlife, you don’t need to know the name of a species to admire its beauty or its adaptations.

Spiders, of course, are most famous for the production of intricate webs, and the geometrical precision of some webs is as remarkable as the strength, pliability, and versatility of the silk used to construct them. Perhaps half of the world’s roughly 40,000 known spider species create webs, varying in design from the well-known round, net-like structure to sheets and funnels. Some webs serve mainly as shelter; others are nets to trap prey, usually capturing a random sample of whatever small invertebrates are flying.

While a web seems like a huge project, I’ve watched a spider spin one in about an hour. And although the fragile structure is easily damaged by wind or large insects, a spider doesn’t much care: it’s typical behavior for a spider to eat its own web and recycle the protein into more silk, and many web-weavers do this every day even if the structure is undamaged.

But many spiders have little use for webs. Wolf spiders — generally large, hairy, free-living spiders — run prey down or ambush it on the ground (think pint-sized tarantulas). Most are reportedly nocturnal, though some species are readily observed on the Vineyard during the day. The wolf spiders I’ve seen taking prey don’t appear to be at all fussy: beetles, flies, and other spiders are among the food I’ve seen them with.

Similarly active are the aptly named jumping spiders, stout, medium-sized and usually dark in color, which have evolved acute vision and the ability to leap many times their body length. (Though they don’t form webs, these little athletes can spin silk and may use a strand as a sort of safety line when leaping.) Several members of this group turn up around or even inside houses; while they look menacing, these are docile animals that flee rather than fight, and I’m happy to have them around for their insect-eating talents.

Also worth watching for are crab spiders, so named because their shape and leg configuration make them resemble crabs. Many of these spiders are brightly colored, camouflage for their favorite ambush site: concealing themselves in flowers, crab spiders wait for a fly, wasp, or bee to visit the flower for pollen or nectar, and then the spider — well, you can guess the rest. Crab spiders sucking the juices from the husk of an insect are a common sight if you spend much time with wildflowers.

While the multitude of spiders and the diversity of the habitats and hunting methods make these arthropods formidable hunters, spiders can be prey as well as predator. A bird like the Carolina wren, for example, is optimized for spider-hunting. Churning up leaf litter on the ground, or investigating crevices in bark, wrens snap up spiders in their fine-tipped beaks, and spiders may represent more than 90 percent of a wren’s diet at some times of year. Spiders themselves cheerfully eat spiders of other species, and many predatory insects take spiders and other small invertebrates indiscriminately.

Most interesting are certain wasps that deliberately seek out spiders (often a particular species), paralyzing them with a sting and then dragging them to a burrow the wasp has prepared. Inside the burrow, the wasp lays its eggs on the immobilized spider, which, because it is not actually dead, stays fresh until the wasp eggs hatch. The larval wasps feed to maturity on the remains of the spider, eventually emerging to mate, dig their own burrow, and provision it with more spiders.

While many types of spiders may succumb to such wasps, it is usually wolf spiders that I’ve seen being attacked by wasps; often, the spider is much larger than its conqueror, and this pattern of predation is a fascinating thing to witness. But it’s a pretty ordinary example of the intricate ecological relationships spiders are involved in. Hate them, if you must. But give spiders some respect for their talents and importance.