Spiders are as familiar and well known to most people as they are disliked. Spiders come in all shapes, sizes, and colors, and despite your reluctance to admit to any benefit from spiders, all spiders are ecologically beneficial as they feed solely on insects and other arthropods. Spiders help reduce pest populations in and around homes, landscapes, gardens, and crops. There is a lot to like about spiders, but first, you have to get past the myths, misinformation, and general disgust.
But to back up a step, what are spiders? In a phrase, spiders are eight-legged arthropods. Arthropods are animals with a unique combination of characters: segmented body, an exoskeleton; that is, an external skeleton (rigid protective "shell" rather than bones, and jointed appendages - mostly legs, but also mouthparts and antennae.
Spiders are in a class called Arachnida that includes the spiders, mites, ticks, scorpions, and related animals. It is a widely diverse and well-known group whose members have two body parts (a fused head and thorax called the cephalothorax plus an abdomen) and four pairs of segmented legs attached to the cephalothorax. Arachnids do not have antennae, and finally, I am personally grateful for one thing, spiders never have wings!
Late summer through fall is when spiders attract the most attention. Spiders such as the garden spiders are fully grown, and their webs made of radiating lines and concentric circles glimmer with due on damp mornings. Fall is also when spiders that live and grow outdoors through the summer become accidental invaders and wander indoors by mistake. Outdoor spiders that wandered into the house are no happier being stuck indoors and unable to get out than you are about them being stuck there.
Hunting spiders such as the common wolf spider occasionally enter buildings through gaps or cracks around windows and doors or other openings in the course of their active hunting. Other spiders wander in by mistake while searching for new web sites. Invader, outdoor spiders usually live for less than a day or two, and they cannot reproduce in the house.
Effective management of home-invading spiders starts with the same exclusionary techniques used to keep out the weather. Seal cracks, gaps, and other openings and repair windows and doors (especially the door sweep), so they fit tight. Insecticides applied outside the structure have little if any benefit and will not provide long-term prevention. Vacuum or sweep up occasional invaders and discard.
Are spiders dangerous?
Nearly all spiders are harmless. Spiders are timid and will retreat if they can. We are not "food" for spiders. They do not bite to feed on you and usually will not attempt to bite humans unless held or accidentally trapped. Most common Iowa spiders have fangs too small or weak to puncture human skin. Only two of the hundreds of species found in Iowa may be considered dangerous. Fortunately, both the black widow and brown recluse are very rare. See "Are Spiders Poisonous?"
Why are we so afraid of spiders?
It's beyond my comprehension if fear of spiders is something we are born with (innate) or something we learn (conditioning). I suspect, as with most complicated topics, it's a little of both. There is a wealth of technical and non-technical writing on the subject. Another possibility is that it is the media’s fault! Feel free to explore.
I was intrigued to learn what makes spiders "scary" to so many people (up to 30% of the U.S. population may suffer from arachnophobia according to one source). According to an old study of college students in London, spiders' most-fearsome characteristic was "legginess" followed by sudden and speedy movements, hairiness, and "crawliness." Why would the addition of two more legs make spiders "leggier" than insects?
What About Spider Bites?
Spiders very rarely bite people and far less than is generally assumed. Most spiders are harmless to people and are incapable of biting, even when coaxed. "Spider bite" is a grossly overstated diagnosis and appears to be a euphemism for "unexplained skin irritation." Ambiguous symptoms such as redness, swelling, cramps, severe pain, or even necrotic lesions can be caused by other factors, including other diseases, medical conditions, and bacterial skin infections. The venom of all but a very few spiders is not dangerous. On the rare occasions where a spider bite is medically significant, the wound gets infected, the same as any other puncture wound.
Of particular concern is attempting to identify "spider bites" by comparison to images on the internet. Posted pictures of "spider bites" are usually wrong, and because of individual body reactions, no one can identify a spider bite from skin irritation. What most often passes for a "spider bite" is rarely caused by a spider but is much more likely to be due to any of dozens of other causes. Unless you see a spider in the act of biting you, don't assume that a spider caused a wound. As an example, read how MRSA is misdiagnosed as brown recluse spider bites. Or see this lengthy review about how spider bites are over-rated.
Do you swallow spiders while you sleep?
Most certainly not. The myth that the average person swallows eight spiders per year has persisted for much longer than you would expect for an item of such nonsense. As stated by Snopes.Com over 19 years ago, This "statistic" that the average person swallows eight spiders per year "was not only made up out of whole cloth, it was invented as an example of the absurd things people will believe simply because they come across them on the Internet."
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