Spiders are Nature's own architects
Summertime. The mere mention of the word conjures up
pleasant images of Fourth of July picnics, fireworks and swimming holes. Mention the word spiders to some people
and it’s enough to make them break out the nearest can of Raid insecticide or
run in the opposite
direction. Chances are you’ll run
into a spider inside or outside this summer, but hey; don’t panic. They are just looking for a meal like
the rest of us and keeping our summertime activities a little more enjoyable.
Unlike
the movie “Arachnophobia,” spiders are not looking at us for mealtime. They dine on most insects that usually
bother us like flies, fleas and mosquitoes. “They are beneficial,” said John Fardal, biology teacher and
entomologist at San Antonio College.
“They are predators that live in almost any habitat such as grass,
water, soil and attics.”
Spiders
belong to the class known as Arachnida, which means it has only two major body
regions, the cephalothorax (combination of head and chest) and an abdomen that
has no appendages. They have eight
legs and no antennae.
Spiders
go back 300 to 500 million years, Fardal said. “They haven’t changed much, they’ve just gotten smaller.” The word Arachnida comes from Greek
mythology. A woman named Arachne was a
skilled weaver who got into a contest with the goddess Athena. Arachne won the
contest but Athena destroyed her work. Distraught Arachne hung herself. Feeling pity for her, Athena turned
Arachne into a spider.
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| The Texas brown tarantula can be found scurrying across Texas' highways. (Mothore photo) |
For
a few weeks in the summer, male tarantulas can be found scurrying across Texas
roads and highways, apparently searching for mates. July is usually when tarantula eggs hatch. The female can lay 100-1,000 eggs.
Tarantulas do bite, as do most spiders, Fardal said, but the tarantula’s bite
is generally not serious to humans.
The name tarantula comes from the city of Taranto in southern
Italy. It was originally applied
on to a European spider, not related to the tarantula. It was believed in the 15th
to 17th centuries the bite of the European tarantula caused the
disease tarantism, which caused people to break into a frenzied dance.
Spiders
bite their prey with their fangs which secrete histolytic enzymes, Fardal said. These enzymes destroy healthy tissue
allowing the spider to suck juices out of its prey for nourishment. “The spider’s bite rots out the skin,”
he said. If left untreated, the
wound will spread causing more tissue damage. Treatment involves antibiotics
and removal of the dead tissue, Fardal said.
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There are three species of black widow spider
living in Texas. (Wikipedia photo)
|
Only two spiders exist in Texas
that prove deadly to humans, he said. They are the black widow spider and the
brown recluse. The black widow
(Lactrodectus hesperus) is found anywhere a web can be constructed, from ground
level to trees and bushes. The red
or orange hourglass shape on the bottom part of its abdomen identifies them.
Its bite is often not painful and can
go unnoticed, but its venom cases abdominal pain in humans, along with muscle
pain, swollen eyelids, profuse sweating, alternating dry-mouth and salivation
and paralysis of the diaphragm. Injections
of calcium gluconate relieve the pain and antivenim counteracts the toxin, but
no first aid treatment is available.
Female black widows can eat their mates, Fardal said, but this doesn’t
occur as often as most people think.
Three species of widow spiders live in Texas. These are the Western black widow, the Southern black widow
and the Northern black widow.
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| The brown recluse has six eyes and a violin-shape on top of its body, and long, thin legs. (Ladyb695 photo) |
The
brown recluse spider (Loxosceles devia) also causes the same symptoms in people
as the Black Widow. This spider
has six eyes and has a violin-shape on the top of its cephalothorax. It resides under rocks, bark, log piles
and indoors. Mating season occurs
between April and July for the brown recluse. The female can produce 250 eggs. Its bite causes hemolysis, or damage to red blood cells by
allowing hemoglobin to leak out and shut down the kidneys.
Keeping these and other spiders out of one’s
home is easy, Fardal said. Two
effective methods are vacuuming and dusting. Dusting kills spiders because dust accumulates on them and
dries them out, Fardal said. Sealing
up cracks in walls and windows with a silica gel keeps them out as well. For outdoor eradication, Fardal said pesticides with pyrethrin are
effective. Pyrethrin is a nerve
poison, he said, which can burn the skin if not handled properly.
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| Spider silk is as strong as steel. Scientist want to synthesize it for use as surgical sutures and underwater adhesive. (Malacara photo) |
Besides
causing summertime panic and snatching up insects, spiders are contributing to
the ever-changing field of biotechnology.
Researchers at Cornell University in New York have worked on
synthesizing spider silk for use as surgical sutures. Spider silk would make the perfect suture because it’s
highly resistant to climate changes, bacteria, enzymes and fungal growth. The only problem is scientists can’t
mass-produce it because of its complex protein structure. Besides, spiders aren’t as big as
cows. Household spiders have to
spin for at least two days to produce enough silk to sew up even the smallest
wound.
The U.S. Navy recently gave a grant to researchers at Utah State University to study spider silk for possible use as an underwater adhesive. This type of silk is called piriform, which spiders use to anchor their draglines and to glue joints in their webs together, according to scientists. It attaches to almost anything and works when wet. The key lies in decoding spider silk's complex biochemical structure.
Further Reading
Unraveling the Weave of Spider Silk
Navy Bets on Spider Silk Research
Jackman, John. A
Field Guide to Spiders and Scorpions of Texas. Houston: Gulf Publishing,
1997.
© 2013 Martin Malacara
