Can I toss that bug outside during winter?

Do most bugs that you would find inside a home able to survive? For example, should I help rescue fruit flies and put them outside or are they better to remain inside? I know most spiders will die if you put them outside, but I’m just not sure about bugs such as moths, larger flies, ladybugs etc. I get worried about opening windows and doors in case they become trapped!

Hi. I live in Rhode Island, so it’s pretty cold here right now. There’s a ladybug living in my kitchen. Can I assume it’s too cold for him to live outside? He can stay inside as long as he wants, but I don’t want him to starve. What do they eat? Should I put him in a room that has potted plants? Or does he eat other bugs? Not sure what to do. I don’t want him starve inside the house, but I also don’t want him to freeze outside. What should I do?

The other day I caught a spider and put it outside. It was around 30 – 40 degrees Fahrenheit outside at the time. The spider was small, maybe the size of a US dime, yellow, and somewhat fast moving. When I put him outside I noticed that instead of moving fast, he walked slowly. I started to wonder if the cold (my concrete patio) was bothering him. Would he freeze to death out there? Or go dormant somehow? What if it’s even colder, like 0 degrees Fahrenheit?

If the cold does bother (or kill) spiders in the winter, do you have any recommendations on removing spiders I catch in the house without killing them? I’ve thought about putting them in my attached garage instead, which isn’t heated but isn’t quite as cold as outside.

During the winter, we get a lot of questions from people asking whether they can put insects outside while it’s cold outside. Or questions about why insects are even inside in the first place.

Hidden TreasureI think it’s a good question, because it exposes something of a riddle. Insects appear every year, so they have to survive the winter somehow…but they die if you toss them in the freezer. The insects you see inside are moving around, but the ones outside aren’t moving around because you can’t see them.

So are there differences between the ones you find inside, and the ones that stay outside? Do those differences mean that they can’t move between the two habitats, like they do in the warmer seasons?

As I said…these are excellent questions, and the answer depends on an understanding of the challenges insects face during winter.

Winter kind of sucks if you’re a bug. There’s no food, and it’s cold outside. It’s not really good for most insects.


Most insects avoid winter, through each of two means. Some, like Monarchs, will escape in space by traveling to warmer climates. The bugs people find inside during the winter escape in time by hunkering down and sleeping through the hard seasons. Entomologists call this sleep diapause.


When insects spend the winter outside, they do so in areas protected from the weather. During the fall, they look for areas to spend the winter…and houses provide a lot of really good areas for this. The area between the siding and the house often resemble the areas where bugs normally spend their winter vacations. They tend to find their way inside while searching for those areas, or even from those areas if there are cracks around the house.

Ladybird aggregation

Asian Ladybird beetles hibernating in a windowsill. Image credit: Gilles san Martin. License info: CC-by-SA-2.0

While they’re looking for a sleeping space, a lot of physical changes happen to insects to condition them for overwintering. These changes are brought on by shorter day lengths, and longer nights. The nature of these changes is pretty complicated, but they allow insects to either keep from freezing or survive freezing. Bug scientists call this conditioning period prediapause.

During prediapause, a lot of stuff can happen. Freeze avoiding insects will fill their blood with sugars, fats, glycerol, and antifreeze proteins which stop ice crystals from forming. Freeze tolerant insects will stock up on things like ice-binding proteins, which act as caps that blunt ice crystals and keep them from shredding cells.

So there are differences between insects during the winter and during the summer, and those differences are pretty important in handling insects during these months.

When insects are exposed to warmer temperatures, the things which allowed them to withstand the winter months go away. To the bugs it doesn’t matter whether the warmer temperatures are from being exposed to warmer air within the house, or due to the weather getting warmer. The warmer temperatures are what tell the insects to stop making the things that keep them alive during winter.

Without these things which keep them alive, they can no longer withstand winter conditions. By the time you’ve found them inside, they’re no longer able to survive outside.

Based on the emails we get on this topic, there’s really two main types of insects we hear about.

Keep Them Alive Until Spring

Keeping the insects alive is really just a simple matter of keeping them clean, fed and hydrated until spring. Every insect needs slightly different care, but I’ve selected the two most common species we hear about to teach people how to do this.

Stink Bugs

We get a lot of messages from people who get Brown Marmorated Stink Bugs inside during winter. These insects are typically pests of orchards, and other agricultural systems…which means their food is pretty widely available in grocery stores.

When they’re outside, they will eat stuff like apples by piercing the fruit with their mouthparts. To recognize a food source, it needs to have some sort of skin over it.

So they can be kept at room temperature and fed using cut apples, with the skin on them. A relatively simple tank setup is really all that’s needed, since they’ll be able to survive until the spring on the sugars from the apple alone.


The other insect we see a lot is the Asian Multicolored Ladybeetle, which feeds on aphids. Since this species is a predator, their care is a bit more complicated.

Although this species is predatory, they can subsist on some plant-based substances. In particular, this species will eat sugar to keep their energy levels up. In captivity, honey is used to supply sugars. Since honey is viscous, entomologists will dissolve it in water at a roughly 10 to 1 ratio of water to honey for them to eat. Soaking a cotton ball in the solution, and providing it in a bottle cap, will keep the insect from drowning. Crushed-up bee pollen, supplied in a bottle cap, can provide a protein source for longer keeping.

Keeping the animal in a cooler environment, like a refrigerator, will keep it alive until the weather is warm enough for it to survive.


Spiders have the least complex care requirements. To keep them alive, they need a place to build a web and a food source. Fruit flies or mealworms, which can be bought from a pet store, are sufficient to supply spiders with food and water. A light misting should suffice to supply additional water, if needed.

Freeze Them

I know this is a really unpalatable option to most of our readers, but I did want to say something about the ecology of these animals.

The Brown Marmorated Stink Bug and Multicolored Asian Ladybeetle are both invasive species. The Brown Marmorated Stink Bug is a pest of agricultural systems, while the Asian Ladybeetle is an insect which has been implicated in pushing out native ladybird species. Although they’re found inside houses during winter, they’re really not the best things to have around. As a result, scientists are trying to limit their damage in certain areas.

Either releasing a single individual back into the environment, or removing an individual by killing it, won’t make a big impact on their populations. However, from the perspective of an environmentalist, the best thing you can do is to freeze them.

The Bottom Line

If you want to return an insect (or spider) you find inside back to the outdoors, you need to take into account its physical condition and the environment. If they’re active during winter, they’re not in any condition to survive outside. Consequently, the only option is to care for it until the weather is warmer.

Procure food and a water source for the animal, which may depend on what you’ve found. If you keep everything clean, and non-mouldy, they should survive a few weeks until spring.

That being said, insects are common in the environment and raising insects can be hard. If you can’t keep them alive, don’t worry about it…they’re going to be around next year so you can try again if you want.


About Polistes fuscatus

Hello, I'm the friendly admin for the Ask an Entomologist blog
This entry was posted in Uncategorized. Bookmark the permalink.

1 Response to Can I toss that bug outside during winter?

  1. fooangel1 says:

    Have lady bug in hotel room, less than 30 degrees outside. Can I take it on plane to Florida and let home go in warm weather? Would it survive?


Discuss with Us

Please log in using one of these methods to post your comment: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s