Although it’s not unusual to find a caterpillar or two crawling across your carpet in the spring, a caterpillar infestation can be a lot more serious than you know. Although you may think of them as cute and fuzzy rather than pests, the truth is caterpillars can cause lots of destruction and wreak havoc on local fauna.
Caterpillars can get into your house in several ways. They may enter through holes and cracks near windows, doors, chimneys, and crawlspaces, or they may hitch a ride on plants and animals. They may also have been born inside, from moths and butterflies that came in and laid eggs in your home months ago.
Read on to learn about why and how caterpillars come inside, and what to do when you find them. Let’s get to it!
Why Do Caterpillars Come into My House?
Caterpillars may come into your house for a variety of reasons. Most species have a similar lifestyle, with adult moths or butterflies laying eggs and producing larvae, which grow in size as caterpillars until it is time for pupation and to emerge in their final form.
They may create cocoons in trees, in leaf piles or soil, or under the edge of your roof, among other locations.
Typically, caterpillars are active at only certain points of the year, such as during their feeding and growing cycles. Some, like that browntail moth, have two active cycles a year in the spring and fall, as reported by the Maine Forest Service.
During their life, caterpillars will seek out foliage to eat to grow and prepare for pupation. They also may seek out safe places to build their cocoons. During either one of these times, you may find them inside your home, as they scout out safe places to eat and hide.
And once they are inside, unlike mice or birds, they will likely not make their way back outside again without some help. This may leave you with a gathering of caterpillars in your house (and a big mess to clean up), so it’s in your best interest to stop them from getting access to your home in the first place!
Here’s How Caterpillars Actually Get Inside Your House
Just like other pests, caterpillars are pests of opportunity and will use any sort of gap or crack in your home’s exterior to make their way inside in search of food or a place to build a cocoon.
Here are some of the most common ways that caterpillars will get inside:
Caterpillars are getting in through Open Windows or Doors
The most obvious way these creepy-crawly pests will get in is if you invite them!
If you tend to leave doors and windows open (like on warm summer days or so pets can easily get in and out), caterpillars are free to come and go as they please.
Caterpillars Enter On Other Animals
Speaking of pets, caterpillars may not need a gap or a hole in the wall, they may choose to hitch a ride instead.
As your dogs, cats, or other animals explore your yard, garden, or other areas of your property, caterpillars may fall or crawl onto their fur, only to let go when they return inside.
The good news is that you can stop a caterpillar in its tracks by doing a quick check of your pet before they come back inside the house. The bad news is, if your furry friend is used to coming and going as they please (like through an installed pet door), you may not spot the caterpillar before they move in.
In this case, you’ll need to rely on other methods to take care of your pest problem. Keep reading below to see our favorite ways to get rid of caterpillars, and discourage them from hanging around your home in the first place.
Cracks are letting caterpillars into your home
One of the most common ways caterpillars can get inside is through cracks and gaps around the structures leading into/out of your home, as well as spaces around the foundation and roof.
Pests may use spaces around windows and doors, piping, and vents to get inside your walls and travel throughout your home.
To close these spaces, use an exterior caulk product to seal any gaps less than ¼ inch. If you have a larger area, you’ll need to use either a foam filling product like Loctite Tight Foam or wire mesh to ensure there’s no space big enough for a caterpillar to squeeze through.
Caterpillars may also use the space under doors themselves if there is a gap between the door threshold and the bottom of the door. You can use a threshold extender like Holikme Door Draft Stopper to close this gap, eliminating one entranceway for caterpillars and other crawlies.
Be sure to do a thorough examination of your home’s exterior in the winter to identify any areas of concern before caterpillars appear, and pay particular attention to commonly missed areas like under the eaves and roofline and along the foundation.
You may also want to pretreat along the base of your home’s foundation by applying a perimeter product.
Holes in Screens and Covers Let caterpillars in
Holes in window screens or vent covers are an open invitation to any caterpillars trying to make their way inside. Dryer vents, chimneys, and even crawlspace holes can all be covered with a combination of wire mesh screens or plastic covers to can prevent pests large and small from entering.
Even if you do have some sort of barrier installed, over time, they may become damaged, causing holes to appear and making them less effective.
That’s why it’s important to conduct a yearly (or more often) inspection of your home to identify what areas caterpillars and pests might be using to get inside your home.
Caterpillars are coming in On Plants
Sometimes, caterpillars aren’t actively trying to get into your home, and merely find their way in by accident! One common way this can happen is if the caterpillar is already living on an outside plant that you bring inside.
This may happen if you take some of your houseplants outside to get some sun, or it may occur when you bring veggies, fruits, or herbs in from your garden. You may also find that a plant you get from your friend or a garden store has come along with a surprise, in the form of eggs laid on the underside of leaves!
That’s why it’s important to check over your plants (just like pets), before bringing them into your home.
A quick scan of leaves and stems (especially the underside) can help limit the number of caterpillars in your house and may save your home, yard, and garden from infestations in the future.
caterpillars Were Born There!
If you’re seeing a lot of caterpillars, it’s probably not because they’re making their way from inside. Rather, tons of caterpillars at once indicate they were born inside!
Keep an eye out for moths and butterflies flying around inside. If you find them hanging out in one area, they may be laying eggs, so it’s important to remove them promptly and keep an eye on what rooms you find them in.
How Do I Get Rid of Caterpillars In My House?
If you can’t discourage caterpillars from coming inside through prevention alone, you may find that you’re in the position of needing to remove your problem physically.
I don’t recommend grabbing a caterpillar with your bare hands.
Instead, try picking up the caterpillar with a Ziploc bag, paper towel, or using garden gloves. From there, you can take care of your problem by dropping them into a bucket with dish soap or by using a spray such as Monterey B.t. Organic Caterpillar Spray.
Avoid dropping any caterpillars outside on the ground, though. They may find their way somewhere to cocoon and keep an infestation going, or, like the University of Minnesota states about the tomato hornworm caterpillar, they may burrow into the soil, to emerge later as a moth.
If you put them outside where they have access to the ground, you risk keeping their reproduction cycle going.
Check out our guide on what attracts caterpillars to your yard if you’re finding them outside – better to stop them before they get in your home anyhow!
How Do I Keep Caterpillars Away For Good?
The most effective way of keeping caterpillars from getting inside your home is through physical prevention.
That means sealing up cracks and holes in your walls and around windows and doors, using screens and covers to discourage caterpillars from using crawlspace or dryer vents, and inspecting any animals and plants as they come in the door.
As a backup (in case some caterpillars still make it inside), you’ll want to use some products in your home to further discourage caterpillars and stop them from making themselves too comfortable.
One natural method that we like is using scents that caterpillars dislike to keep them away. Caterpillars actually have quite poor eye sight and a heightened sense of smell.
To make that more clear, their eye sight is actually TERRIBLE. So, they really rely on their sense of smell to find food and sense shelter near them.
If you use strong scents in potential caterpillar attracting areas, you can discourage caterpillars from making their way inside your home.
If you’re interested in this method, I highly encourage you to take a look at our guide on the 7 scents that caterpillars hate where we go over what works in detail!
What The Heck Are Those Tiny Caterpillars in My House?
The University of Maryland reports that seeing very small caterpillars in your house may mean you’re seeing “first stage caterpillars” (such as the gypsy moth, where caterpillars eventually become larger second stage caterpillars). Or they may not be caterpillars at all.
Instead, you may be seeing carpet beetle larvae which can appear like small caterpillars. If you see these, take care of them immediately with a product like Reefer-Galler SLA Cedar Scented Spray, otherwise, you risk them making a feast of curtains, the fabric on furniture, clothing, and any other cloth in the house!
Otherwise, if what you’re seeing is not a carpet beetle larvae, you may be seeing one of a variety of species. Unfortunately, over the years several invasive species of caterpillars have spread, meaning the assortment of species you could see has increased.
Depending on where you live, the most common caterpillars you might see are the tomato hornworm, browntail, spongy, gypsy, box tree moth, walnut, or yellow-necked caterpillars.
Whether you’re seeing small or large caterpillars, you’ll want to take care of them quickly, to avoid a continuation of their life cycle (which will only prolong your infestation). You’ll also want to deal with them quickly to avoid your houseplants being eaten, or to avoid them cocooning and emerging as moths in your home.
Interested in learning more? Take a look at our more detailed guide on how to keep caterpillars out of your home!
Caterpillar is a general term for a wide variety of larvae of both moths and butterflies.
Caterpillars typically live outside feasting on trees, fruits, or veggies and cocooning in canopies or the ground, but may come inside homes and other structures when they’re looking for food or a safe place for pupation.
These pests will use open windows and doors or gaps and cracks in your home’s exterior to come inside, or they may hitchhike on animals or plants.
With a little bit of preparation and time, you can adequately seal up your home and discourage most caterpillars from coming inside your house. And, if you utilize a variety of products in combination with closing up gaps and holes, you can mount an effective defense against these creepy-crawly insects.
And if you still need help though, don’t hesitate to contact a pest professional using our Pest Pro finder tool. We’ll help you to find someone qualified and local to take care of your caterpillar problem quickly and easily.
Hasnaoui, Foued, et al. “Insecticidal effects of essential oils from six aromatic and medicinal plants on the pine processionary caterpillar (Thaumetopoea pityocampa Schiff).”
IstiantoandAlbertusSoemargono, Mizu. “The Effect of Citronella Essential Oil on Controlling the Mango Red-Banded Caterpillar, Noorda albizonalis Hampson (Lepidoptera: Pyralidae).” Jordan Journal of Biological Sciences 8.2 (2015).
Plata-Rueda, Angelica, et al. “Lemongrass essential oil and its components cause effects on survival, locomotion, ingestion, and histological changes of the midgut in Anticarsia gemmates caterpillars.” Toxin Reviews (2020): 1-10.
Rosen, Ted. “Caterpillar dermatitis.” Dermatologic clinics 8.2 (1990): 245-252.
Zack is a Nature & Wildlife specialist based in Upstate, NY, and is the founder of his Tree Journey and Pest Pointers brands. He has a vast experience with nature while living and growing up on 50+ acres of fields, woodlands, and a freshwater bass pond. Zack has encountered many pest situations over the years and has spent his time maintaining and planting over 35 species of trees since his youth with his family on their property.
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