Updated: Nov 12, 2020
I think spiders might be out to get me. Before I begin to explain, this is not some clever attempt at a spooky themed post for Halloween. Over the last few weeks, I have encountered quite a number of orb weaving spiders that have constructed several rather large webs in many frequently walked areas of my property. I am even greeted by one every day that sits in a large web in my driveway just a few feet from where I park my car. Normally I would not be alarmed by this but in the past month I have seen more of these orb weavers than in previous years. Just when I thought I had seen enough, what do I see when looking out of the window behind my desk at the Science Museum? That’s right, it was an orb weaver. Had it climbed all the way up to the third floor just to block my view?
Spiders don’t exactly have the best reputation. In fact, arachnophobia is one of the most common fears in the world with more people being afraid of spiders than any other animal. To most people, they are creepy little creatures that appear in all sorts of places just to freak us out. Some say we are never more than 3 feet from a spider, they bite us when we are sleeping, and we even swallow about 8 spiders per year. They aggressive, dangerous, and scary. In truth, spiders are none of these things and undeserving of the reputation that precedes them, but they continue to be feared.
Arachnids are a class of arthropods which includes spiders, scorpions, mites, and ticks. Spiders are the largest group of arachnids with over 48,000 discovered species. While they share many similarities to their arthropod cousins, insects, people often mistake the two as being a part of the same group. As with all arthropods, both have distinct body segments, jointed limbs, paired appendages, exoskeletons, and an open circulatory system. Unlike insects, spiders have 8 legs instead of 6, 2 distinct body segments instead of 3, no antennae, no compound eyes, and fangs.
Spider webs can be quite intricate and an amazing spectacle to see. They are made of silk which is produced by spinneret glands. Spiders typically have two to three different spinnerets. Some may have just one of these glands and others, like my friend the orb weaver, can have as many as eight. To make a web, a spider will climb a tree, a bush, or another high point and shoot a silk thread into the wind and onto an anchor point on a branch, another tree, or even a person (my orb weaver friends tried to do this to me). It will then walk along this thread, strengthening it with more threads until it is strong enough to support the rest of the web. A framework is then constructed, followed by the inner construction. The finishing touch is to go over the web, making sure it’s sticky enough to catch prey. Webs are constantly undergoing repairs from damage and spiders will remake their webs everyday if they need to. Only half of all known spiders actually make webs but their silk has a variety of other uses including climbing, hanging, building egg sacs, wrapping up prey, and even flying through the air.
If there is any characteristic of spiders that make them seem creepy, it would be their fangs. Known as chelicerae, these fangs are perfectly designed to inject venom into their prey. A spider will keep its chelicerae folded up until it perceives a threat or is ready to bite. As scary as they seem, and despite all the myths, spiders do not typically bite humans, even dangerous ones. If they do bite, it’s because they feel threatened. People have a natural curiosity as to whether certain spiders are venomous or not and the answer is almost always yes. Just about every species of spider makes venom. Venom is produced by glands at the base of the fangs and sent through ducts when the spider injects its prey. There are two general types of venom: neurotoxic which effects the nervous system, and cytotoxic which kills cells and tissue.
The primary diet of most spiders are insects but some larger species are capable of taking down small mammals, birds, and reptiles. When they eat, it will inject venom into prey in order to kill or paralyze it. A spider will also inject digestive enzymes into prey, liquefying it before it is ready to eat. Of the 48,000 species of known spiders, less than 100 have venom that can affect humans and only a couple dozen have the potential to kill humans. The deadliest spider in the United States, the Black Widow, accounts for about 2500 bites per year but very few of those turn out to be deadly. On average, there are approximately 7 deaths per year from spider bites in the U.S., less than dogs, cows, or wasps.
While they invoke our innermost fears, spiders just prefer to sit and wait until the opportunity for a meal presents itself. As scary as they are, there are a number of benefits to keeping spiders around. As predators, they maintain a natural balance in the environment, controlling populations of pests that carry disease or can damage crops. By some estimates, a single spider is capable of killing up to 2000 insects per year. Researching spiders has provided many benefits as well. Studying spider-silk has led to numerous potential uses including ropes, parachutes, and lightweight clothing. Spider-silk has medical benefits as well in the development of human tissue and it is believed to have healing properties. Venom is also widely studied for potential treatments of pain, stroke, and cancer. Spiders are fascinating creatures that are misunderstood. Instead of squishing the next spider you see, it may be more beneficial to let it be.