Speaking of Spiders
Monday July 24, 2006 Well, we know that J. Jonah Jameson doesn’t know squat about Spider-Man, but sadly, many of us seem to channel the libelous editor when we are confronted with real spiders. We think we know what spiders are up to; we know that spiders are no good – a menace to us all! Few animals are more maligned and misunderstood than spiders. They are called ugly, deadly, even insects! I, and a great many other arachnophiles would argue that spiders are not ugly. On the contrary, they can be quite beautiful (see the cute little jumping spider above!) And since death from spider bites is extremely rare (an average of 4 deaths annually) it’s hardly fair to call them deadly, unless you’re also willing to call dogs deadly. (They cause an average of 20 deaths annually, five times that of spiders!) Finally, spiders are most certainly not insects! (No offense to any insects in the audience.) Spiders are in the phylum arthropoda, along with insects and other animals with exoskeletons and jointed legs. But spiders, ticks, mites, and other eight-legged, two-body-region-having arthropods are in the class arachnida while insects have six legs, three body regions, two antennae and belong to the class insecta. Spiders are distinguished from other arachnids by the way their two body regions are joined. The cephlothorax is the “head” region of the body. It is where the spider keeps its eyes, mouth, brain, stomach, pedipalps (appendages between the mouth and front pair of legs), and legs. The abdomen is the rear of the spider and consists of the heart, digestive tract, reproductive organs, lungs, spinnerets and silk glands. The cephlothorax and abdomen are joined by a thin stalk called the pedicel. In other arachnids the two body regions are joined broadly, often without a pedicel. All spiders are carnivores; they eat other animals, usually insects. To this end, all spiders have fangs, and all (except two small families) have venom glands. But only 25 of the 50,000 known species (that’s 1/20th of 1%) have venom capable of causing illness in humans, to a greater or lesser extent. Besides venom, several spiders have a unique – and often beautiful – way of catching their food: webs. The common garden spider (argiope aurantia) and house spider (achaearanea tepidariorum) are well-known examples. Not all spiders construct webs however. About half of all spiders are hunting spiders and search for food using their sense of touch, smell, and sight. Examples of hunting spiders include wolf spiders (family lycosidae) and jumping spiders (family salticidae). While these hunting spiders do not usually construct webs to capture their prey, they can produce silk, and use it for a variety of purposes: draglines, safety lines, or the construction of shelters or egg sacs. Spiders are an important part of our ecosystem. As predators of insects they help control the insect population, and as prey, they feed birds, lizards, and some small mammals. So don’t be a J. Jonah Jameson; learn to appreciate spiders, and appreciate all they do for us. Perhaps the most important thing spiders can do is provide us with a constant source of amazement and wonder. Sean “Spider-man” Blevins Ijams Outreach Coordinator Bibliography: Crawford, Rod. “The Spider Myths Site.” The Burke Museum of Natural History and Culture, May 24, 2006 http://www.washington.edu/burkemuseum/spidermyth/index.html Levi, Herbert and Lorna. Spiders and Their Kin. St. Martin’s Press, New York. 2001 Various Authors. “Articles on-line.” American Tarantula Society, May 24, 2006 http://atshq.org/articles/index.html |
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