They are everywhere!
A new study published today details just how many arthropods are in people’s homes. And it’s a lot! The study was done by researchers at North Carolina State, the California Academy of Sciences (CAS) and the North Carolina Museum of Natural Sciences. Actually one of the researches from California Academy of Sciences (Dr. Misha Leong) is a friend of my from graduate school, so yay UC Berkeley! Anyway, they found a lot of bugs.
Surprisingly, this is the first study to evaluate arthropod diversity in US homes. We tend to think of our houses as mostly free of animals that are not pets. But this study shows that to be pretty much universally untrue. This study looked at 50 homes around Raleigh, NC, a total of 550 rooms. Only five rooms were totally free of arthropods! 24-128 arthropod families were found in each house. The majority of them were flies, spiders, beetles, and wasps (including ants).
Here is a figure from the paper that I really like. It shows the proportional diversity of what was found in all rooms.
Interestingly, pest insects were not as common as benign insects. However, cockroaches were found in 82% of the homes sampled. Ants, not surprisingly, were found in every home (further supporting my theory that ants are going to take over the whole). Spiders were also found in every home. They types of spiders varied a lot, but cobweb spiders were always present (not surprising to those of us to regularly dust away their webs). The full data table is presented in the paper.
Book lice (Family: Liposcelididae, Order: Psocodea) and gall midges (small flies) were very common and are generally not well known. I don’t have pictures of them yet, but I’ll just give some basic details in case you want to keep an eye out for them.
Gall midges are in the family Cecidomyiidae (Order: Diptera). These guys are small (2-3mm) and delicate. Their antennae are generally long compared to their body. The authors suggest that these are common in homes simply because they are common in the environment outside of homes. The diversity of small flies is not well studied, and there are really quite a lot of them around.
Book lice are related to the kind of lice that attack people but are not the same. They feed on fungus, decaying stuff, and stored grains. This diet allows them to do well in people’s homes. The study’s authors speculate that perhaps the high humidity in NC helped the book lice do well in that environment. So they might not be as common elsewhere. Wikipedia has a picture of one if you want to keep an eye out in your own home.
Lastly, I want to highlight one key point from the discussion. There is a great diversity of arthropods in (and around) our homes. Instead of being annoyed or frightened by it, I encourage people to embrace the small wonders of the tiny worlds all around us. Happy insect hunting!