I know, I know – you hate spiders. Spiders are the creepiest of all terrestrial life, you say. Spiders like to sneak into houses and bite unsuspecting children, you say. Spiders are as evil as snakes and - as everyone knows - snakes are pretty evil, you say. But allow me to posit this idea to you: You are wrong and unnecessarily burdened by cultural prejudices. In a country that takes great pride in its ideals of independent “free” thought, I see a lot of people who are slaves to unfortunate misconceptions.
Let’s first consider an obvious undeniable fact. The existence of spiders is as valid as the existence of all other life forms, including human life. Does that seem like a rather cold view of the world? Not at all; I’m just not human-centric in my judgement of nature. All life on earth has evolved over the eons to arrive at this moment in time precisely as we see it (or, one could make the argument, as imprecisely as we see it). Tapeworms, wolves, nematodes, whales, humans, and spiders all have equal claim for their place on Earth.
Let’s also admit that we are apparently biased against spiders because most of them aren’t as pretty as, say, butterflies. If spiders had beautiful wings, would we be less inclined to squish them with a shoe? Most spiders are cryptic in coloration because they depend on stealth to capture prey. So, let’s agree not to judge them too harshly on aesthetics. Beauty, after all, is only skin deep.
Besides the facts that spiders are a part of our evolutionary heritage and that we humans are easily manipulated by cultural prejudices, you might reasonably ask, “What’s so interesting about spiders?” My answer is, “Everything.”
There are almost 40,000 known species of spiders in the world. They vary in size from almost microscopic (Patu digua) to as big as a dinner plate (Theraphosa blondi – the goliath bird-eating spider). Most spiders are small with a body length not exceeding half an inch.
Yes, it’s true that spiders aren’t vegetarians. They are evolutionarily obliged to kill things for their meals just like lions, lizards, and anteaters. Spiders don’t have a choice to eat vegetarian food like humans do. Almost all spiders are venomous (excepting feather-legged orb weavers) but very few have a bite that can harm humans. The venom is needed to quickly subdue prey. Keep in mind that most female wasps and bees are venomous too, thus the pain of the sting.
As pointed out above, spiders aren’t usually noted for their beauty, but there are certainly those that are arrayed in brilliant colors. Some tarantula species (Mygalomorphs) and many jumping spiders (Salticids) are flamboyantly decorated. (For jumping spiders, the colors serve a purpose in their mating rituals, but it is unclear what evolutionary advantage tarantulas get from being brightly decorated.) There are a few spiders – such as crab spiders – that can adjust their color from white to yellow to match the flower they’re on.
Even though some spiders have exceptionally good eyesight (wolf spiders and jumping spiders), most have poor eyesight and depend primarily on “touch” for survival (another reason why color isn’t important to the majority of spiders). The hairs on their legs serve the same purpose as whiskers on cats – to feel the world around them. The webs built by many spiders also serve as an extended network of nerves that signal when prey has been snagged.
And those webs! Spiders spin silken threads from glands on the posterior end of their abdomens. This silk, in comparable thickness, is stronger than steel. Spiders use the silk for capturing prey, encasing their eggs, for temporarily tying down their mates, and for building a safe hideaway. Webs take on different shapes depending on which species makes them. For instance, if you see an orb web, you can be assured that a black widow - a cobweb weaver - didn’t create it. The bolas spider (Mastophora spp.) captures moths by lassoing them with a strand of sticky thread. Diving bell spiders (Argyroneta aquatica) actually live under water in an air bubble held in place by silk. And let’s not forget the silk used for flying! Newly hatched spiderlings often fly to distant places by climbing to the tip of a leaf and releasing a long thread that allows wind to carry them aloft like a kite; it’s called “ballooning”.
Finally, here in Arizona we have many distinctive spiders. There are a few species of Loxosceles spiders that many people erroneously call “brown recluses”. (A brown recluse is Loxosceles reclusa and lives in Texas, east to Georgia, and up into Virginia. They do not naturally occur in Arizona.) Our Loxosceles species are supposedly less virulently toxic in their bites. We also have black widows (Latrodectus spp.) which have bites of “medical significance”, but usually stay in their webs unless molested by humans. Normally black widows are very shy spiders and will fall to the ground and play dead if humans try to capture them. One of the most interesting of the local spiders is the spitting spider (Scytodes sp.), a very small and slow-moving creature that captures prey by spitting a sticky venom. And, of course, we have desert tarantulas, the largest spiders in the United States.
Spiders are important for the fact that they eat mostly insects and other spiders (black widows, by the way, frequently eat scorpions!), thus keeping down populations of potentially harmful pests like mosquitos and flies. If a spider should be wandering around in your house, it is simply because it’s looking for prey. It is never in your house to attack you. Keep your house a little cleaner and clutter off the floor and you will see far fewer spiders.
We as humans have a limited natural ability to study nature. Our unaided eyes can only see a small portion of the stars (and none of the billions of galaxies) in the Universe. Nor can our unaided eyes see the microverse of bacteria and viruses, etc. However, we do have the ability to take the time to pay attention to the smaller creatures around us and, in the process, learn something about ourselves and our place in Nature. Spiders are often maligned and needlessly killed due only to ignorance-driven fear. Much of that fear is culturally-based - a learned reaction rather than a natural response. Here we have an opportunity to reconsider these small animals and to marvel over the fascinating lives they live. More knowledge is always a good thing.