Where Do All the Mosquitoes Go in the Winter?

Where do all the mosquitoes go in winter?

Summer evenings by the pool, lake or barbecue mean mosquitoes. But what about in winter when we are mostly indoors? When the weather cools, these bloodsucking pests are rarely seen.

But where are they going?

Warm, wet conditions are suitable for mosquitoes

Mosquitoes have complex life cycles that depend on water supplied wetlands, floodplains and water containers due to seasonal rainfall. Depending on whether we experience a summer under the influence of El Nino or La Ninamosquito populations will change in different ways.

During the warmer months, their life cycle lasts about a month. Eggs laid around the water hatch and the immature mosquitoes go through four stages of development. Larvae then turn into pupae, from which an adult mosquito emerges, sits on the surface of the water for a moment and then flies away to buzz and bite and continue the cycle.

Water is crucial, but temperature is also very important. Unlike warm-blooded animals, mosquitoes cannot regulate their own body temperature. The warmer it is, the more active mosquitoes will be. There are usually more of those too.

But once cold weather arrives, their activity slows down. They fly less, bite less often, reproduce less and their life cycle is longer.

Temperature also plays a role in determining the ability of mosquitoes to spreading viruses

Cold weather isn’t great for mosquitoes, but millions of years of evolution have given them a few tricks to survive

Mosquitoes don’t disappear completely

On a sunny winter afternoon, you may notice the occasional mosquito in your backyard. Not as much as in the summer, but they are still there.

Some mosquitoes disappear. For example, the activity of the pest mosquito Culex annulirostristhought to play an important role in the spread of the Japanese encephalitis virus in Australia, drops drastically when temperatures begin to drop under 17.5

Studies in Sydney have shown some mosquitoes such as: Culex annulirostris, to disappear. Others, like Culex quinquefasciatus and Culex molestus, stay active all winter. You may not notice them (unless they come into your house to buzz over your ears).

Mosquitoes can disappear in diapause

We are familiar with the idea that mammals hibernate in winter, but mosquitoes, like many insects, can enter a phase of inactivity that we diapause

Once it gets cold, adult mosquitoes find shelters such as tree hollows and animal burrows, in the cracks and crevices of bushland environments, or in garages, basements or other buildings around our homes, suburbs and cities. These mosquitoes may only live for a few weeks in the summer, but if they go into diapause, they can survive for many months into the winter.

Mosquitoes can also be found in frozen waters, whether it’s a bucket of water in your backyard or an almost icy wetland. For example, there is a group of mosquitoes that belongs to the genus scallop dia whose larvae attach themselves to the sunken parts of aquatic plants and can survive the cold winter temperatures. Their development slows down dramatically and they remain in the water until spring arrives.

All their eggs in one winter basket

Some mosquitoes survive the winter thanks to their eggs. Mosquito eggs can be incredibly resilient. They survive drying out in hot and salty coastal wetlands during the summer, as well as frozen in snowy creeks during the winter.

In coastal areas of Australia, eggs of the salt marsh mosquito (Aedes vigilax), sit completely safe on the floor. Once the weather warms up and the tides bring water to the wetlands, these eggs are ready to hatch.

There is also a special mosquito in Australia known as the “snow melt mosquito” (Aedes nivalis) whose eggs survive under snow and emerge as soon as the snow melts and fills ponds, creeks and wetlands in the Alpine regions.

Does it matter where mosquitoes go in winter?

It’s not just the mosquitoes that survive the cold months either. Viruses, such as Japanese Encephalitis Virus or Ross River viruscan survive from summer to summer in mosquito eggs, immature instars or diapause adults.

Knowing the seasonal distribution of mosquitoes helps health authorities design surveillance and control programs. It can help understand how invasive mosquitoes survive conditions in Australia outside their native range by hide from the coldsuch as in rainwater tanks.

Even mosquitoes typically found in tropical locations can adapt to cooler climates

This knowledge could even uncover the chilly crack in the mosquito armor that we can use to better control mosquito populations and reduce the risk of disease outbreaks.


Cameron Webbclinical associate professor and chief scientist in the hospital, University of Sydney

This article was republished from The conversation under a Creative Commons license. Read the original article

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