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Early signs point to a severe mosquito season

As the thick snow cover melts, puddles form ideal breeding ground for mosquitoes.

Hyttynen iholla.
The summer looks promising for mosquitoes. Image: Miika Silfverberg
Yle News

All signs point to a severe mosquito season, come summer.

Snowy winter months like we've just had generally create ideal conditions for the insects, according to Lappeenranta biologist Kimmo Saarinen.

Thick snow cover currently envelops most of Finland. According to the Finnish Meteorological Institute (FMI), Eastern Finland has seen a record amount of snow in February.

As the snow melts, puddles become breeding grounds for mosquitoes. It takes approximately two weeks for a newly-hatched mosquito to take flight.

When the snow starts melting, there will be a wealth of puddles, says Saarinen. However, he cautions that we'll have to wait and see in order to make more accurate predictions.

A warm, rainless spring would ensure the snow evaporates. On the other hand, milder weather with increased rainfall would produce even more standing water.

The more puddles we have, the more mosquitoes we'll get, Saarinen says.

Last summer's heat spurred population crash

Last summer most of the mosquitoes in Finland were gone by July. This was due to a sudden heatwave that led to them hatching simultaneously and puddles drying up.

Mosquito season generally lasts all summer. Different mosquito species have life cycles and egg incubation periods of varying lengths, ensuring eggs keep hatching throughout the summer. The temperature of the bodies of water that serve as breeding grounds also affects the incubation period.

Snow cover also provides ideal living conditions for billions of other small animals, like mites and earthworms, says Saarinen. A snowless winter would create much harsher conditions for these organisms, he points out.

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