In defense of the (mostly) harmless spider

With apologies to those who suffer from arachnophobia (the fear of spiders), this week’s article covers a member of the animal kingdom that isn’t usually thought of as beneficial.

Spiders often get a bad rap. They’re portrayed as evil or deadly creatures in movies. Large, black bodies with eight spindly legs are commonly seen as spooky decorations during Halloween. Real-life spiders are viewed as frightful critters to be screamed at or smashed. Unfortunately, we’ve been conditioned from childhood to treat spiders with revulsion.

Not all cultures fear spiders. Spiders were symbols of wealth and protection from poverty in ancient Rome. The ancient Chinese believed anyone who saw a spider drop from its web was blessed with good luck. The spider-man character Anansi, the embodiment of wisdom and storytelling, is prominent in the folklore of west Africa, the West Indies, the Caribbean, and even the southern U.S. (as “Aunt Nancy”). Spider Woman is a powerful figure in the mythology of southwestern Native Americans.

While all spiders are predatory and make venom, very few spider species pose a serious threat to humans. Although spider bites can be painful, they’re more of a nuisance than a health threat. Furthermore, spiders typically shy away from people, and will bite only if disturbed.

Let’s examine some basics of spider biology. They’re not insects or “bugs,” (all of which have six legs, wings, and two eyes); instead, spiders are wingless and have eight legs and eight eyes. Spiders belong to the Arachnid family, a group that also includes ticks, mites, and scorpions. Female spiders lay eggs that hatch into spiderlings that look like miniature adults and grow to maturity in several stages.

A few of the most common spiders in California are the:

Orb-weavers or garden spiders: These spiders — often beautifully patterned or ornamented — spin the classic spider web, with a spiral of silk overlaid on spokes that radiate from a central point.

Jumping spiders: These fairly small and hairy spiders don’t spin webs; instead, they stalk and pounce on their prey. They can jump up to 50 times their body length by harnessing the energy of a chemical reaction in their hindmost legs! They’re also the largest family of spiders worldwide.

Black widows: This is one of many spiders classified as “cobweb weavers.” The female is a jet-black spider with a red hourglass-shaped pattern on the underside of her large, round abdomen; the male is smaller, brown, and non-poisonous. Black widows spin irregular, amorphous webs using silk that is extremely strong and sticky. If bitten by a female, seek medical care, since this is one spider whose bite can be harmful and sometimes even fatal to people (especially children, older adults, or those with compromised immune systems).

A well camouflaged crab spider capturing a housefly (Photo by Kathy Keatley Garvey)

Here are some fascinating facts about spiders and the beneficial role they play in our ecosystem and lives:

  • Spiders are vital for controlling insect populations, and they eat other garden pests too.
  • Spiders are found on every continent except Antarctica.
  • Spiders are a crucial food source for many birds, lizards, snakes, and even some small mammals.
  • Many hummingbird species rely on spider silk to bind and anchor their nest materials.
  • Web-weaving spiders have special organs called spinnerets that they use to create “silk” from liquid protein. Many filaments are combined to make a single silk strand.
  • Spider silk is the strongest-known natural material; it’s pound-for-pound much stronger than steel, and it’s inspiring innovations in materials science and mechanical engineering.
  • Scientists are studying spider silk for various medical uses since it’s strong, biodegradable, and tissue compatible (not subject to rejection).
  • Chemicals derived from spider venom are used to treat several diseases.

Leave spiders in your garden where possible so they can continue to perform their beneficial role. If spiders make their homes in places where they’re a nuisance — inside homes, near entryways and porches, on outdoor seating, or in woodpiles — it’s best to use non-toxic methods of removal. Catch-and-release techniques and simple spider-catcher devices can be used to relocate spiders without harming them. Brooms, dusters, and vacuums can be used to rid an area of spiders and their webs. Sticky traps can control spiders in and near homes without poisons. Insecticides should be avoided both indoors and out since they’re minimally effective and potentially harmful. Rather than killing all spiders within reach, take a few minutes to watch them in action and appreciate the vital role they play.

For a fascinating time-lapse video of orb weaver web construction, watch this YouTube video.

For gardening-related questions, call the UC Master Gardener office at 209-953-6112, or use our website: http://sjmastergardeners.ucanr.edu/CONTACT_US/.

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