Mosquitoes are one of the greatest banes of summertime. They seem to be everywhere, and are the source of a major phobia for many people. They can spread disease, chase you away during a picnic, and are generally a nuisance. But then they seem to just go away.
As the summer weather cools, mosquitoes become scarce before vanishing altogether, only to appear late the following spring as if they’d never left.
Today we’re going to take a look at the role temperature plays in mosquito biology and habits, as well as what temperatures will actually kill mosquitoes. There are a few fascinating things to discover along the way, so let’s dive right in!
What Temperature Kills Mosquitoes?
Mosquitoes can’t survive temperature extremes, but exactly what temperature will kill them can get a little complicated.
To get our answer, we must first touch upon a few facts of mosquito behavior, then get into how each stage is affected by temperature shifts.
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Why You Should (and Shouldn’t) Worry About Mosquitoes
Mosquitoes have quite the bad reputation, but they’re not (always) as bad as they’re purported to be. For example, male mosquitoes only live for a short period of time and don’t actually feed on blood. In fact, the females only drink blood when they’re preparing to reproduce. The rest of the time, mosquitoes are actually pollinators.
That’s right, mosquitoes are good for your garden. Believe it or not, they’re also a species of fly, despite looking nothing like cluster flies or horseflies. There’s even another type of fly called the crane fly that feeds on mosquito larvae. But most of us know flies as simply being disease carrying pests and never stop to think of their purpose.
And that brings us back to mosquito behavior and how it relates to temperature. As with other pollinating species, mosquitoes have adapted to be most active when their food is available. Thus, when the plants go dormant, so do the mosquitoes.
Some are capable of overwintering in a state similar to hibernation while others lay their eggs and die as winter approaches.
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Adult Mosquitoes vs Temperature
Mosquitoes are best adapted for summertime when plants are generally in full bloom. Their optimal temperature is 80 degrees or warmer, but they begin to slow down as the temperature drops to 60 or below. In most cases, it’s believed that 50 degrees or lower will kill a mosquito.
But this is only scratching the proverbial surface. Male mosquitoes will only live for a few weeks at most and will usually die before cold temperatures even have a chance to arrive.
Females will usually live longer and many species (keep in mind, there are more than 3,500 species of mosquito across 112 genera) go into a hibernation-like state called diapause when temperatures drop.
This means that the cold may not immediately kill a female mosquito or her eggs.
Read Also: Can Roaches Freeze in Winter?
Mosquito Eggs vs Temperature
Speaking of eggs, these little things are truly durable. Mosquito females who don’t survive into winter will lay their eggs in water or tree hollows where the eggs will be encased in ice throughout the winter.
The eggs can then hatch the following spring. However, a mosquito egg is so durable that it can still successfully hatch years after being laid!
In some species, the female will lay a single egg on top of still water where it floats until hatching. In other cases, the eggs are deposited a bit above water level and will hatch when the water level rises and gets them wet.
So you can already see that there are many places and conditions in which eggs are laid, which also means temperature will affect the eggs of one species differently than another.
So where do we go from here? The egg will hatch into a larval stage which is aquatic in nature, before becoming a pupa and hatching as an adult. And the larvae are surprisingly vulnerable.
Mosquito Larvae vs Temperature
Mosquito larvae may be aquatic, but they breathe air, meaning they’re constantly diving for food before coming back up for air.
Cooler water temperatures will slow their metabolism and thus their movement, while freezing the surface will cause them to drown. Pupal mosquitoes can also drown in this way.
How to Interrupt a Mosquito’s Nap
Back around 2008, Ohio State University revealed the ongoing research into Culex pipiens, a common overwintering species known for spreading West Nile virus. The experiments themselves revolve around charting genes which regulate insulin signaling. This turns out to be a vital factor in the mosquitoes being able to survive.
According to this research, when the days begin to shorten, it triggers a hormonal response in the female mosquito that causes them to begin storing up fat. This fat is necessary for the female to survive through diapause, awakening in the spring to finish developing her eggs. And this is where things get interesting.
The researchers artificially altered the length of days and nights, interrupting this hormonal response for several days. This prevented the mosquitoes from storing up fat, which also insulates against cold. Within four days, mosquitoes which had entered diapause began losing their fat and 80 percent died within three weeks.
Meanwhile, another group had their days artificially shortened after the eggs had matured and were ready to deposit. These mosquitoes stopped egg development and entered diapause. As these biological functions are also necessary for the West Nile virus to overwinter, this research has a lot of implications.
However, for our purposes, we can focus on the following takeaways:
- Overwintering mosquitoes rely on day lengths to judge when winter is coming so they can store up fat and go into diapause before the cold can hit.
- Interrupting a mosquito’s diapause results in a high casualty rate.
- Mosquitoes can be fooled into entering or exiting diapause.
- Because the mosquito triggers for diapause are light-based and not temperature-based, it can be possible to use temperature as a weapon without the mosquito being able to enter diapause, thus killing it and its offspring.
Read Also: Can Coconut Oil Repel Mosquitoes?
So What Temperatures Work Best?
We did warn you this was a complicated topic, and thus far, the only firm answer is that some mosquito adults will die if the temperature drops below 50 degrees while others will enter diapause. We also pointed out that freezing an infested body of water can suffocate larval and pupal mosquitoes. But there has to be more of an answer to this question, right?
Let’s look at heat for a moment. Scientists have found that exposing mosquito larvae and pupae to temperatures of 115 degrees will kill them in about 15 minutes while adults lasted for about 30. This research focused on two species, but it’s suspected most species share this vulnerability.
At 125 degrees, adult mosquitoes tend to die in 10 minutes or less (although this is not true of all species). The eggs died in under two minutes. Even more heat tolerant species have a very short life expectancy if exposed to temperatures over 140 degrees for any period of time.
Thanks to the research, many exterminators are able to focus on heat treatments instead of fumigation for some mosquito infestations.
But what about cold? The amount of variation between species means some will indeed die when it drops below 50 degrees, but to kill off those capable of diapause, you will need to reduce the temperature to around -1 degrees Fahrenheit.
Unfortunately, you’re not likely able to emulate this amount of cold in your kitchen freezer.
Alternatives to Temperature Warfare
We’ll be perfectly honest here: Research has shown that it may be possible to use light and temperature as an effective killer for most species of mosquito, but that research is ongoing.
And outside of pouring boiling water into an infested bird bath or hiring an exterminator with proper heat equipment, you’re not likely to have much luck fighting mosquitoes using temperature as your weapon.
Your best weapons are a lot less complicated, however. For example:
- You can attract insectivorous birds to your yard who will gladly hunt down mosquitoes.
- Eliminate all sources of standing water from your property (as long as the water is moving, mosquitoes can’t use it).
- You can also introduce some species of fish to your water features that will eat mosquito larvae.
- When outside, make use of citronella candles, and avoid leaving any external lights on at night when you’re not using them.
- Because it’s very possible to get a mosquito infestation indoors, make sure all your screens are in good shape and lack any tears.
- You should seal up any entry points and never leave a door or window open in the summer if there’s no screen.
- Fix any leaks within the house, which can attract all sorts of pests or lead to mold or rot.