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November 17, 2023
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January 18, 2024
How Minnesota mosquitoes spend their winter depends on the species.
The ground may not yet be covered in snow in the Twin Cities, but winter is here and adult mosquitoes are not out and won’t be actively seeking bloodmeals for several more months. However, as tried and true Minnesotans know, it doesn’t matter how cold, snowy, or abnormal a winter might be, the mosquitoes always return.
While we are enjoying our respite from being fed on by these annoying bloodsuckers, some might be wondering - what do mosquitoes do in the winter in Minnesota? Like many other insects in our northern climate - they spend the colder months in diapause, a period of suspended activity or development. The form that takes depends on the type of mosquito.
We have approximately 52 species of mosquitoes in Minnesota, which can be categorized into around nine different genera. All species follow the same basic life cycle of egg, larva, pupa, and adult. Most species overwinter as eggs, waiting for snowmelt or spring and summer rains to trigger a hatch and for stagnant water as a place for larvae to develop. Some overwinter as adults, hibernating in caves, sewers, or other structures that protect them from the elements. Others are hearty Minnesotans and stay as larvae in the frigid cold waters of ponds and wetlands all winter long.
Let’s take a closer look at the winter behaviors of the more common Minnesota species:
Larvae may begin to appear as early as March or April in cold wetlands and marshes.
Spring Aedes aka “snowmelt mosquitoes”
Species Include: Aedes punctor, Aedes excrucians, Aedes stimulans
These are some of the first mosquitoes one might encounter as the snow melts and the temperatures warm up in early spring. These species are most active in May and June, but have a long life span and some can live until August. Spring Aedes have been responsible for some of the District’s mosquito activity peaks during the past three drought years. Spring Aedes mosquitoes are univoltine, meaning they only have one brood of offspring per year, so the eggs produced enter diapause and usually do not hatch during mid- to late-summer rains, but wait until the following spring.
Spring Aedes mosquitoes overwinter as eggs.
Summer Aedes aka “summer floodwater mosquitoes”
Species Include: Aedes vexans, Aedes trivittatus
In a typical summer, when people are complaining about annoying mosquitoes in Minnesota, they are probably talking about Aedes vexans. While a few years of drought have decreased the activity of this rain-dependent species, this is historically the most abundant summer mosquito in Minnesota. Summer floodwater mosquitoes are multivoltine, meaning they will lay eggs multiple times throughout a season and their activity ebbs and flows based on rain and temperatures. These mosquitoes can remain active and new broods can continue hatching into September or even October if the temperatures stay warm, but typically the eggs laid late in the summer enter diapause when the sun’s angle sinks.
Summer Aedes mosquitoes overwinter as eggs.
Culex larvae often develop in catch basins and the adult mosquitoes might also take refuge there during winter months.
Culex Mosquitoes
Species Include: Culex tarsalis, Culex restuans, Culex pipiens
Culex mosquitoes are notable for being the primary vectors of West Nile virus in Minnesota. Their larvae develop in standing water which can include wetlands and man-made habitats like containers and catch basins. Culex mosquitoes emerge in May and remain active until early fall and birds are their primary bloodmeal source. However, these opportunists will also feed on humans or horses from time to time, which is why they remain a public health concern. When temperatures dip below freezing, a lot of water sources where Culex mosquitoes lay eggs also freeze. The adult female mosquitoes will then find a warm refuge in sewers, caves, animal burrows, or other habitats. When the temperatures warm back up, these adults will re-emerge and resume reproduction, which means these might be some of the mosquitoes found on those sporadic warm spring days.
Culex mosquitoes overwinter as adults.
Cattail Mosquitoes
Species: Coquillettidia perturbans
The cattail mosquito might have the most unique overwintering behavior of them all! This distinctive species is a univoltine mosquito that typically emerges from the water around the end of June or early July in Minnesota. The females seek a bloodmeal (this aggressive species prefers to bite humans) and then deposits their eggs on water near emergent vegetation. The larvae hatch in late summer and attach to the stem of a cattail plant (hence the name) or other aquatic vegetation and use a siphon to draw oxygen from the plant’s roots. Larvae remain in the water for up to 9 months before emerging the following summer and starting the cycle all over again.
Cattail mosquitoes overwinter as larvae.
MMCD checks wetlands for cattail larvae in the fall. The mosquitoes won't emerge from the water until the following summer.
Other Species
Culiseta inornata are also known as the “winter marsh mosquito” because they can sometimes appear in winter months and they are usually the first species to emerge on warm spring days. These mosquitoes feed on mammals and in rare instances may bite humans.
Culiseta inornata mosquitoes overwinter as adults.
Anopheles mosquitoes are a worldwide menace because they are the genus known for carrying the parasites that cause malaria in humans. In Minnesota, Anopheles are not a malaria threat, but several species are common throughout the state.
Anopheles mosquitoes overwinter as adults.
This is the winter behavior of some of the more common species we have in our little slice of the world. Throughout the world there are over 3,000 species of mosquitoes and they all base the timing of their life cycles on the climates in which they inhabit. Now that it’s December, Minnesotans can enjoy a break from our unofficial state bird and know that while they may not be biting, they are still out there as eggs, adults, or larvae.
Have any questions for MMCD that might make a good future blog post? Send them to us!
Sources:
- MMCD Technical Services Staff and Publications
- Amateur Entomological Society Glossary
- Rutgers Center for Vector Biology
- University of Florida Featured Creatures
