Spotlight on Spiders

Little Miss Muffett’s Entomology Connection

A simple nursery rhyme about a fictitious little girl? Hardly. Miss Muffet was actually the stepdaughter of Dr. Thomas Muffett, a 16th century British entomologist. It has been reported that this learned naturalist would mash common spiders into pulp and spoon feed them to his stepdaughter as a remedy for the common cold. No wonder she was frightened of spiders!

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Entomology 101:
Basic Spider Anatomy
Spiders are divided into only two body regions: the cephalothorax (head and thorax) and the abdomen. The spider’s eight legs are attached to the underside of the cephalothorax, and the eyes are found on the top front, or carapace, of the cephalothorax. Most spiders have eight eyes, although some of the more primitive families have fewer. The arrangement of these eyes is important for identification.

The mouthparts consist of the chelicerae, which are tipped with fangs, and the pedipalps or palps. While the mature female’s palps are the same thickness from base to tip, the end segment of the male’s are greatly enlarged. Prior to mating, sperm is placed in this segment and is then inserted into an opening underneath the female’s abdomen called the epigynum. The identifying characters of a spider’s anatomy are shown in the illustrations at right.

The abdomen is a non-segmented region which contains the heart; digestive, respiratory and reproductive system; and the silk glands, which extrude silk through the spider’s spinnerets.

 (Source: Mallis Handbook of Pest Control, 8th Edition)

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Arachnological Fun Facts
Spiders are among the most intriguing of all pests, but they also have a fun side. If you don’t believe it, consider these fun facts:

The word “spider” is derived from the Old English verb “spinnan,” meaning “to spin.”

The oldest known fossil record of spiders dates from 130 million years ago in the Early Cretaceous period.

While the life cycle of most spiders is approximately two years, tarantulas have been known to live up to 25 years in captivity. In fact, The Tarantula Times reports they have become popular pets because they are “quiet, noiseless creatures that take up little or no space at all, and are extremely easy to care for and feed.” Sounds like the perfect roommate.

More than 35,000 species of spiders occur worldwide, including 3,000 in the U.S.

An abnormal fear of spiders is known as arachnophobia, made famous by the movie of the same name starring actors Jeff Daniels and John Goodman, who played a PCO named Delbert McClintock. The Steven Spielberg-produced movie didn’t do much for the industry’s image, but it grossed $53 million in domestic box office receipts.

Spiders have a circulatory system characterized by a heart, arteries and veins, but no capillaries. Their blood is a pale blue color.

Spider webs are made from spider silk that is produced by silk glands beneath the abdomen. Not all spiders spin webs, but they all produce silk.

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Tarantulas are among the largest spiders in the world. In fact, the species Theraphosa blondi is known as the bird-eating tarantula of South America, so named by explorers from the Victorian era who witnessed one consuming a hummingbird.

Spiders liquefy food before consuming it by injecting digestive fluids into the paralyzed prey and then sucking it dry, leaving only the exoskeleton.

When Marvel became the first comic book company to be listed on the New York Stock Exchange in 1991, the Wall Street Journal announced “Spider-Man is coming to Wall Street.”

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How to Identify Brown Recluses
So many spiders get misidentified as brown recluse spiders yet they are relatively easy to identify. The key characteristic that separates them from most other spiders is that they have six eyes. Most spiders have eight eyes arranged in two rows of four eyes each. However, recluse spiders have six eyes arranged in three pairs called “dyads.” There is a dyad at the front top of the spider and another dyad on each side further back.

The famous violin marking (fiddle back) is often touted as the primary identification character for brown recluse spiders. It is not. While the marking is usually clear on adult brown recluse spiders, the violin marking can be inconsistent. It varies in intensity, fades in alcohol and may not be readily identifiable in many cases. Therefore, it’s important to familiarize yourself with the key identifying characters of brown recluse spiders including:

• Body not more than ³⁄8-inch long
• Six eyes arranged in three pairs of dyads
• Long, thin, uniformly colored legs without spines and with two tarsal claws
• Violin marking on the top of cephalothorax (for adult brown recluse and a few other recluse spiders)

Brown recluse spiders prefer dry, dark, undisturbed areas. They spin a sticky, irregular and flattened web that is not easy to see. They spend the day in their web and forage for prey at night. Large numbers often can be found in a small area. Critical inspection areas indoors include attics, piles of debris, storage areas, closets and utility rooms, crawlspaces, bathroom vanities, under beds, and in shoes, storage boxes and seldom-used clothing.

Most people “know” that any necrotic skin lesion was likely caused by a brown recluse spider. Many physicians agree. As a result, they commonly diagnose brown recluse bites on the basis of such a localized necrosis. Most of these diagnoses are wrong. Bottom line: It is NOT possible to examine a bite and determine that it was caused by a brown recluse spider. Technicians, especially, should never make this diagnosis. Other facts to remember:

• Brown recluse spiders are not aggressive; they bite only when trapped or pinned against the skin.
• Multiple bites are extremely rare.

Source: Techletter by Pinto & Associates,
www.techletter.com