2017-10-19 / Nature

Spiders, Spiders Everywhere

By Charles Avenengo

A field of spiders at home at Sachuest. (Photo by Carmen Rugel) A field of spiders at home at Sachuest. (Photo by Carmen Rugel) "Wherever you sit as you read these lines, a spider is probably no more than a few yards away."

Norman Platnik, American Museum of Natural History

If you don’t like spiders, these are chilling words from the country’s most prolific arachnologist, who has seen more than 1,800 species of spiders in his career.

Currently, there are at least 38,000 types of known spiders in the world, and it is estimated that this number could someday reach 100,000. Furthermore, it is said that a single acre contains 1 million spiders, and in the tropics, the number rises to 3 million per acre.

With such extraordinary numbers, your skin might begin to get itchy. With the arrival of the cold weather, many spiders are entering your home for shelter. Good thing they aren’t bigger, because all spiders are predatory killing machines. They are armed with venom-filled fangs, eight eyes and eight legs, from which tiny hairs smell and sense vibration. Additionally, all spiders produce silk, which is employed in a number of cunning methods to capture prey. To add to the nightmare, spiders employ digestive juices that liquefy and suck out the innards of the victims.

The largest spider in the world is the Goliath spider of northern South America. Eleven inches long, it eats frogs, mice, lizards, snakes and small birds. Goliath spiders and the somewhat similar and more familiar tarantulas have weak venom with bites comparable to wasp stings.

As it turns out, there are two poisonous spider species in the United States; the black widow and the brown recluse. Happily, neither has a range in New England, much less on Aquidneck Island. Instead, they are found to the south. Occasionally, they arrive here accidentally. Last summer, a 5-year-old in Mendon, Mass. was bitten by a black widow. And in September 2015, an East Providence man was bitten by a brown recluse. Both had to seek medical attention.

How these spiders arrived here is a mystery, although generally they are unwitting passengers trapped in various containers. University of Rhode Island professor Dr. Roger LeBrun is fond of telling his introductory entomology classes that in the 1950s, a woman in Providence, after traveling here from Alabama, was bitten by a brown recluse in her hotel room as she was unpacking her suitcase.

Still, it is unsettling to think that no matter where you are, you are never more than a few feet from a spider. What about underwater, you ask? There are water spiders that employ a “diving bell” that enables them to exist and spin webs underwater. They use their legs like a fishing pole to capture insects, and even small tadpoles and fish.

What about in an airplane? Spiders are airborne, too, streaming past your window seat on silken threads. Called aeronaut fauna, similar to many other types of animals, spiders migrate in the heavens. In a process called “ballooning,” spiders tippy-toe on their eight legs up to a suitable launching pad, like the tip of a blade of grass or a fence post. Then they raise their abdomens and release silk. Soon, the spiders are able to gain up-lift by releasing a large number of threads, which fan out from the spider’s body and form a triangular sheet. This is gossamer.

Unlike insects, birds and bats, spiders don’t have wings and this “ballooning” is a physicist’s dream. According to a 1987 "Journal of Arachnology" article, by Greenstone et al.,“The ascent of spiders into the upper air depends on convective updrafts and is affected not only by the velocity of the updraft but also by the mass of the spider and by the drag of the silk thread and balloon.”

But these spiders only migrate by day, so we may think we’re free and clear from spiders on a red-eye flight. Not necessarily. There might be one just below in the cargo hold. Like the woman from Alabama, it is accidentally packed away in a suitcase, and somehow it escapes.

But breathe easy, there is an exception to all this. There are no spiders in Antarctica. Unless, that is, they arrive in a suitcase.

So, just when you think you’ve settled in for the night, remember, at all times, within a few feet of you, a creature with poisonous fangs, eight legs and eight eyes is watching your every move.

Happy Halloween.

Spider Facts and Myths

. Spiders consume more insects than bats and birds combined.

. Abandoned webs are called “cobwebs.”

. An average human dwelling has between 10 and 30 species of spiders living in it.

. House spiders’ feet have hairs that grip surfaces and are able to run up walls. However, they can’t get up a bathtub because the surface is too slippery.

. If a spider web was as thick as a pencil, it could stop an airline jet in flight. Scientists are unable to replicate their strength and elasticity, which would be helpful for items like bulletproof vests.

. It is a myth that humans swallow an average of four spiders throughout their lives while sleeping. A sleeping human’s mouth is not where a spider wants to be.

. Spiders are blamed for all kinds of bites. However, unlike bloodsucking mosquitoes or ticks, spiders don’t feed on human blood. They won’t bite a human unless they feel threatened or surprised.

Naturalist Charles Avenengo has been chasing Aquidneck Island wildlife for more than 40 years.

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