Here's What Spiders Are Up to in Your Home, According to an Expert
If you've spotted a spider in your bathtub, in a bedroom crevice, or crawling on your kitchen floor, rest assured, you're not alone!
Seeing one of these creepy crawlers in your living space isn't indicative of anything weird or gross about your lifestyle. That said, it doesn't make it any easier to deal with.
Because we're no strangers to seeing little critters pop up where we live, we decided to reach out to Biological Sciences PhD student, Catherine Scott, to get the scoop on these uninvited visitors. Keep reading for everything the University of Toronto Scarborough student revealed about what's going on with the spiders in your house.
Sweety High: How did you get into the study of spiders?
Catherine Scott: It was an accident. Basically, I got a summer job as a research assistant studying black widows, I quickly overcame my previous fear of spiders, fell in love, and have been studying spiders ever since.
SH: Why are (most) spiders less scary than we think?
CS: Spiders do not feed on human blood, so they have no reason to bite us unless they feel threatened. Although almost all spiders are venomous (they use the venom to subdue their insect prey), the vast majority would not cause us serious harm even if they did bite us (it would be no worse than a bee or wasp sting). Many spiders have fangs so puny that they would not even be able to pierce human skin. Only a few spiders in North America are potentially dangerous to humans (the widow spiders and recluse spiders), and even they are very shy and rarely bite.
SH: Which spiders are most commonly found in homes?
CS: Cellar spiders, yellow sac spiders, common house spiders and house spiders are all common in homes and all harmless to humans.
SH: How do spiders get into homes (aside from an open window or door)?
CS: They may occasionally come in boxes brought inside from sheds or shipped from other places.
SH: What attracts spiders to a home or a particular location in the house?
CS: We don't know a lot about exactly how spiders choose where to hang out but they will generally go where there is prey available. So if there are spiders in a room, it's probably because there are also insects there for them to eat. There is some research showing that spiders can detect the presence of insect prey based on their smell. Spiders are also often found around outdoor lights, which is a great place to capture night-flying insects like moths that are attracted to the lights.
SH: What exactly are spiders' purposes in the house? What are they doing in there?
CS: The job of all spiders is to eat insects and other arthropods, and that's the same whether they are indoors or outdoors. They are professional pest controllers and are great housemates because they will eat any bugs that are also in your home.
SH: Do spiders know when humans enter a room or are looking at them?
CS: Spiders are very sensitive to vibrations, but most have very poor vision. If you walk into a room, they can probably detect your movements, and also see your shadow, but they probably don't really know you're a human. Often, people tell me that spiders charge toward them and think they're trying to "attack." What's actually happening, in most cases, is that the spider is trying to get away, running toward your shadow, which represents a safe hiding spot.
SH: Is there any way to tell if a still spider is dead or alive, aside from touching them or pouring water?
CS: If a spider is still and you want to see if it's alive, you could gently blow on it or brush its back legs with a paintbrush—this will usually cause them to move away from the air or the touch (or they may curl up into a ball and play dead, a defensive mechanism). I do not recommend pouring water on spiders or grabbing them with your hands. Spiders are often very delicate and could be injured by rough handling.
SH: What are some ways to tell if a spider is dangerous?
CS: The only spiders that are considered dangerous to humans in North America are widow spiders and recluse spiders. North American widow spiders are pretty easy to identify because they're shiny and black with a red hourglass on the underside of their abdomens, and sometimes red on the back as well.
In California, there's the native western black widow, and also the invasive brown widow, which, as the name suggests, is brown, but also with a red or orange hourglass mark on the underside. The brown recluse spider does not occur in California, but there is another related species, called Loxosceles deserta, that can be found in the southern deserts of California. They're rarely seen in and around homes. HERE is a resource on how to tell if a spider is a recluse, and a Twitter account where people can send photos of spiders they think might be recluses.
There are a lot of brown spiders that can easily be mistaken for brown recluses, but most are not recluses and pose no risk to humans.
SH: What can you tell me about the rumor that we swallow spiders in our sleep?
CS: It's false! You don't eat spiders in your sleep—there's no reason they would go in your mouth. Here's a fun video about that:
SH: What are some other misconceptions about spiders, and are there any other general things you think people should know?
CS: Spiders are generally shy and unaggressive, and have no interest in biting humans. When bites do happen, it is often because the spider is trapped between shoes or clothes and skin, and it bites defensively as a last resort. They don't feed on our blood, so the idea that they go into our beds at night to bite us is not based in reality. Spiders never burrow under skin or lay eggs in our bodies (some urban myths talk about such things).
Spider behavior is fascinating, and they are far more helpful to humans than they are harmful. They eat somewhere between 440-880 million tons of insects per year. So the world would be a much less pleasant place for humans to live without spiders!
Some spiders are incredibly beautiful. For instance, check out the courtship dances of the Australian peacock spiders in the genus Maratus. They are like tiny dancing rainbow-colored cats.
Speaking of jumping spiders, they will hunt laser pointer dots, just like cats will!