No matter where you live, it’s tough trying to escape from bugs during the summer.
But when the temperature plummets outside, almost all of the bugs just “magically” disappear.
So what exactly happens to all of the insects during the wintertime? And why do so many of them ride out the winter in your house? And what can you do to prepare for next summer?
We’ll answer those questions in this blog!
Where do most of the bugs go in winter?
*Note: For this whole blog, keep in mind that we’re only focusing on insect survival strategies in parts of the world where the temperatures drop below freezing during the winter.
You’re probably aware that birds like Canadian geese migrate south to escape the winter each year. Amazingly, a lot of insects (especially butterflies), will also migrate long distances to warmer areas of the world during the winter. Monarch butterflies are some of the most stunning examples since they fly hundreds of miles (up to 2,500 miles) from the U.S all the way to Mexico, being driven by earth’s magnetic pole and several other factors. How many creatures do you know that navigate using a magnetic compass? It’s amazing what monarchs are capable of.
The generation of monarchs that fly to Mexico will breed up to a few times during the journey, and a new generation will make the trip back across the United States and Canada once summer roles around again. So the next time you see monarch butterflies in your garden during the summer, they’ll be the children and grandchildren of the ones you saw the previous summer!
Other insects that migrate to escape the winter will also rely on wind currents to their advantage. Since insects are much smaller than birds, a little wind is usually enough to transport many bugs across the globe to escape winter! And what’s amazing about insect migration is that just in the United Kingdom alone, there’s an estimated 3 trillion insects that will migrate to warmer regions of the world. Think about how many trillions more migrate in other parts of the world!
And the biggest insight that scientists are beginning to appreciate about insect migration is that they contribute heavily to the successful functioning of earth’s ecosystems. Besides butterflies, other insects that will migrate include beetles, moths, dragonflies, and the most recent discovery including hoverflies (the flies that mimic bees in appearance). We still don’t fully know how many insect species migrate, but over 70 have been documented just in North America alone!
Physiology of winter “hibernation”
For the creatures that don’t migrate and are forced to ride out the cold, have you ever pondered what exactly happens to insects and larger animals during the winter?
For those of us who experience freezing winters, we’re lucky to have modern indoor heating to keep ourselves nice and warm.
It’s incredible that every animal we see in the summertime has its own unique strategies for winter survival.
Surprisingly, only a few animals are “true hibernators,” like the arctic ground squirrel, which undergoes deep sleep for long periods of time. Big mammals like black bears go through a lighter form of hibernation called torpor, so contrary to popular belief they’re not actually true hibernators. This article explains hibernation in greater detail and more examples of animals that fall into different hibernation categories.
In both true hibernation and torpor, hibernating mammals will reduce their metabolism in order to conserve energy since they won’t be feeding again until the warmer months. They typically store up a lot of fat before the winter since that becomes the main source of fuel that they burn off to survive. Mammals are called “warm-blooded” since they maintain their internal temperature regardless of the outdoor cold.
Insect “hibernation” however has some key differences compared to that of mammals. Since insects aren’t warm blooded, they primarily survive winter by undergoing diapause, which in a nutshell is basically an insect’s way of doing hibernation. Insects that go into diapause have their metabolism slowed down almost completely, and for immature insects (all the stages of growth besides adults), they will completely halt their development until winter ends. In a way, most insects in winter go through a form of cryosleep, not moving at all until temperatures reach a high enough threshold.
More on diapause
So what exactly allows an insect to be in diapause (remember, insect hibernation)?
Let’s take a look at a nice example, the Japanese beetle. You’ve probably seen a bunch of them since they’re not native to the U.S. They can cause a lot of damage to turf grass as larvae and eat up garden plants and fruit trees as adults.
Japanese beetles will lay their eggs in the ground, and the larvae (or grubs) will burrow underground a few inches, all the way to a foot deep! They survive the winter by remaining below the frost line.
During the brutal winter weather of 2019, temperatures in some parts of Minnesota dipped to almost -60 degrees Fahrenheit! As an entomologist, I was curious what would happen to pests like the Japanese beetle since they hunker down underground. To my surprise, they survived this Antarctic-like weather just fine, because during the summer they completely devoured the apple tree in my backyard!
The secret to the Japanese beetle’s ability to survive crazy cold temperatures is a combination of burrowing underground where there’s some insulation, as well as creating their own antifreeze.
That’s right. Besides the Japanese beetle, many insects will survive winter by making antifreeze, which is made up of glycerol and other sugar-based compounds. The glycerol helps prevent ice crystals from forming inside a bug’s body. Some insects even make antifreeze proteins, which specifically prevent insects from freezing to death.
So if you thought the winter would kill off the bugs that you wish wouldn’t come back, unfortunately Mother Nature has made them quite adapted to survive brutal winters year after year.
Looking at other insects, many will be in diapause inside of tree bark (especially wood-boring beetles), under rocks, inside of buildings, and even underwater at the bottom of lakes, rivers, and other bodies of water. Dragonflies, stoneflies, and mayflies (all semi-aquatic) in their immature stage will stay underwater near the bottom of the ground until temperatures rise again. Unlike most terrestrial insects, some aquatic insect species will continue developing and growing even during the winter, although their growth is usually delayed.
Probably one of the coolest examples of winter survival is the snow scorpion fly. Scorpion flies got their name because the males have a tail similar to that of a scorpion, but they’re not actually flies since they belong to the insect order Mecoptera, while flies are a part of the order Diptera. These guys will literally hang out on the surface of the snow when it gets to around 30 degrees Fahrenheit, and will even mate on the surface too. It’s not fully understood how they’re able to comfortably walk across the snow, but we do know that they make a lot of glycerol and antifreeze proteins, probably more than other insects.
Another arthropod that loves snow is a species of springtail called the snow flea. If you ever see a bunch of dark specks moving across the snow, it’s probably them. These little guys belong to the order Collembola, and even though they’re hexapods like insects (having six legs), they’re actually not considered true insects since they have internal mouthparts whereas all true insects have external mouthparts.
So besides all of these critters, what about the mosquitoes?
Where do mosquitoes and other flies go in winter?
Mosquitoes are very intelligent creatures. You might think, “how could such tiny insects be smart if all they do is come after my blood”?
If mosquitoes and other biting flies have evolved to survive harsh, freezing winters year after year for generations, then clearly they must be doing something right. So how in the world do they survive?
Each species may have slightly different strategies, but for many mosquitoes, they will lay diapause eggs, or eggs with a slowed down metabolism and special compounds that allow them to survive freezing temperatures that are normally deadly for a typical insect. Think of it as mosquitoes entering into a cryo-chamber and then as temperatures rise, they awake from their sleep.
Mosquitoes will usually lay their eggs in the soil or in stagnant water. Most of the mosquitoes that ride out the winter underwater will already be in a larval stage.
If we’d have some empathy for mosquitoes, the sad part is that most male mosquitoes die when winter starts, while female adults will survive in diapause, bulked up with layers of fat. Remember that the males never bite people (they exclusively feed on nectar and plant juices), while only the females will seek after human blood.
What about the ants, bees, wasps?
Ants, bees, and wasps are three very closely related insects belonging to the same insect order, Hymenoptera. Yet, their winter survival strategies vary in detail. It’d take a great amount of pages to describe how each species survives cold winter weathers, since there’s an estimated number of 150,000 – 300,000 unique species in Hymenoptera (and most likely more since we’re discovering new species each year). And don’t forget that bees are not just honeybees; there are thousands of solitary bee species where these are bees that live by themselves without any nest mates.
In general, like most other insects, members of Hymenoptera undergo diapause, slowing down their metabolism and movement to conserve energy. They will also make use of glycerol and other antifreeze molecules to prevent their insides from freezing up.
If we’re talking about honeybees, the female workers surround the queen and huddle closely together for warmth, and live off of the honey they would’ve collected during the warmer months. Even though some of the workers will end up dying during the winter, honeybee queens typically won’t lay any eggs in the winter months to maintain enough honey for the hive to make it to spring time.
What about the wasps? Compared to honeybees, wasps tackle winter in a more “deathly” fashion. For social wasps (those that have large numbers of individuals like social bees), the entire colony usually dies during the winter except for the females that mated with males earlier. These females effectively become queens that “hibernate” (undergoing diapause) during the winter months. Hibernating queen wasps will sometimes make their shelter inside peoples’ homes, and you may end up seeing dead wasps by a chimney if you have one. This article explains why that is. For solitary wasps, usually the larvae will survive in a diapause state, waiting for the summer to complete their transformation into adults.
For ants, here’s an awesome video (“How Ants Survive the Winter”) that explains how they employ very similar strategies to that of bees and other insects. To my knowledge, one interesting tactic unique to ants is that some species will coat the inside of their nests with glycerol.
Summing up, social bee and ant colonies are able to survive the cold in large numbers (although a number of members will still die off during winter). Wasps take a more sacrificial approach, with most individuals dying except for the mated queens.
How did insects get in my house during the winter?
You’ve probably thought at some point, “if it’s so cold outside, how did insects just magically appear inside my house then?”
Many insects can take shelter in your home during the fall months (between September and November) as temperatures drop. They take advantage of the small cracks and crevices outside your house that you’re probably unaware of.
One prime example is the Asian Lady Beetle (a type of ladybug), which was introduced in the U.S as a beneficial control of harmful pests. Unfortunately, this “good” bug can behave as a pest since they will often seek shelter inside warm buildings when it gets colder outside. Thankfully, other than the noxious yellow odor they secrete in self-defense, they don’t cause any serious harm to people and only act as a nuisance. Besides ladybugs, you may also deal with box elder bugs in your house during the winter, but like the ladybugs, they won’t cause any harm other than being a nuisance.
The other major way that insects can get inside your house in the winter is if you bring firewood or houseplants from outside during the fall months. How so? If you don’t carefully inspect the plant material, there could be tiny insects eggs already laid, especially from aphids. Gnats, mealy bugs, and spider mites can also find their way in your house by hitching a ride on houseplants if you left them outside during the summer months. With wood, you could unknowingly be carrying termites that live inside the wood, and could end up causing damage inside your house if the termites get loose.
The main lesson from bugs getting in your home is to be vigilant. Always inspect any houseplants and wood if you bring it from outside, and make sure that you’re carefully checking for any cracks and openings around your house if you’re prone to getting bugs inside during the winter.
Preparing for next summer
By now, you’ve learned that insects don’t just magically disappear in the wintertime, but rather, they’re actually waiting patiently for the cold to go away.
With this post, we’ve barely even scratched the tip of the iceberg with the amazing number of ways that different insect species survive the winter. Both beneficial and pest insects will undergo diapause somewhere underground, many will migrate, while others will camp out in the attic of your house.
So, what can you do to prepare for when the “bad,” pesky bugs come out in the warmer months?
- Make sure to inspect and look over any houseplants or firewood that you have in your house. Check for insect eggs, larvae, or cocoons that may have hitchhiked with the plant material.
- Spring-cleaning! Yes, doing spring-cleaning is definitely not in vane. As you spend time preparing for the warmer months, cleaning out any clutter, garbage, and repairing any cracks in your house will help prevent a bunch of insects from invading when summer roles around. If you have a garage and basement, it’s worthwhile to clean those areas out too since many insects like to hide there.
- Make sure that you don’t leave out any open containers outside, especially after it rains in the spring. Since mosquitoes breed in open, stagnant water, you’ll prevent an onslaught of new mosquitoes in your backyard if you work on eliminating their breeding area before the start of summer.
You can also stock up on Trappify’s yellow sticky traps, which will trap fruit flies, gnats, and other small pesky flies that can invade your houseplants. Having these traps on hand before summer roles around will help you be more prepared against flies that end up swarming your houseplants.
It’ll be inevitable that some bugs will make it past the defenses of your home. But with a little preparation before spring, you’ll have less bug problems to deal with, and more time enjoying the summer!