Have you ever been home alone, watching Stranger Things or listening to My Favorite Murder, and started jumping at the sudden hum of the refrigerator, brandishing your ice-cream spoon down the dark hallway to the bathroom? I have good news for you. We are never, ever alone in our homes. We all have other creatures living in our homes, no matter how scrubbed, swept, and sterilized our apartments and houses on the Hill may appear.
From the time that people began living inside dwellings, we’ve had other creatures alongside us. Some are imperceptible, bacteria, viruses, archaea, and fungi. Others, like insects and arachnids, are decidedly more noticeable. In 2016, a press worthy study by North Carolina State University researchers was published, reporting findings from an exhaustive, purportedly first-ever survey of the arthropods (invertebrates of the phylum that includes spiders, insects, and crustaceans) in our homes. Of the 50 houses the authors surveyed in the Raleigh, North Carolina, 100% had arthropods living in them. In fact, they had far more than anyone guessed, and they collected over 10,000 individual specimens representing nearly 600 species of arthropods, with homes hosting an average of 93 species, from 62 families.
Though I doubt this revelation eases your movie induced paranoia, below are five common house guests that you may or may not have even heard of, but may have been living inches from all your life.
1) Booklice (Order Psocoptera) — Unlike their blood sucking cousins, booklice like to chew rather than suck. Mostly they like to munch on fungus, food bits, and other detritus but they will also happily chew on the glue of our book bindings and wall paper and can in some instances infest food. Seeing a few of these opaque flattened creatures is nothing to be alarmed about, but if you happen to collect old books in damp places, be mindful. People often confuse book lice with bed bug nymphs or termites which are far more alarming.
2) Varied Carpet Beetle (Anthrenus verbasci) — If you work in a museum, you know this group of beetles well. The family of Dermestid beetles, to which this species belongs, are useful for helping pick clean skeletons (in a controlled colony), but wreak havoc if loose. Their hair covered larvae eat feathers, skin, fabric, infest carpets, and often create the damage we attribute to “moths” in our wool and linen. The Varied Carpet Beetle was the first species of insect to be shown to have an annual biorhythm, important because their size allows for ease of study in controlled settings.
3) House Centipede (Scutigera coleoptrata) — Fast, many limbed, and alarmingly strange looking – you might never see one of these household predators, possibly a good thing because they look like something out of a horror movie. The good news is that these centipedes are not aggressive and generally shy away from our presence (in extremely rare occasions they can give a painful sting but I’m pretty sure you’d really have to work for it). They are also near the top of their indoor ecosystem, meaning they help control the other species that could be construed as troublesome.
4) Dark winged fungus gnats (Order Sciaridae) — Though little studied (except for a few species that are agricultural pests), you may have seen these tiny flies before. Smaller than a fruit fly, they don’t attract much attention, often living in association with our potted plants, because they like the moist soil, eat the fungal colonies that live there, and the live and dead plant material too. Over-watered plants however are at risk of fungus gnat infestations, which can kill plants (I have done battle with them in several of my pots). Outdoors fungus gnats are part of the nutrient cycle, helping break down leaf litter. In low numbers, they’re just housemates.
5) Silverfish (Order Zygentoma) — I have never seen a silverfish and most of you probably haven’t either. They are nocturnal and tend to stay out of the way during the day. Silverfish represent a group that evolved before winged insects – they’re fairly ancient. They love to eat substances with polysaccharides, starchy things, and have long been considered pests because they will destroy paper, fabrics, and even paints. In movement they wriggle, reminiscent of a fish, but are also fast enough to avoid their predators, like House Centipedes and wandering spiders.
The authors of the study expected to find lots of pest species (specifically species that cause significant harm to people or property), largely because the bulk of study on indoor species focuses on them.
What they actually found was that pests made up a smaller portion of the overall biodiversity of arthropods in the surveyed homes. Most species present were benign, or even beneficial. Before you pull out your Raid and start bombing those dark corners, consider the benefits of biodiversity (another study also suggests that outside ecologies have as much or more to do with indoor life as cleanliness). We heard some negative aspects of the lesser knowns above, but keep in mind that carpet beetles and booklice might just be cleaning up your dead skin and food crumbs, and that silverfish could be helping spread microbes that are beneficial to our immune systems while they slither around at night.
There’s a growing body of research demonstrating that the microbial life perpetuated in biodiverse settings are good for our health. If we actually did what pesticide and antibiotics manufacturers seem to suggest, and kill 99.9% of everything in and around our homes, we might find ourselves in more trouble than before. No, I don’t want a house centipede crawling over my face at night anymore than you. But, I’d rather risk it than suffer from severe allergies. Now if we could only figure out how to get these critters to start paying rent.
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