Mosquitoes, often associated with warm weather, do not simply vanish when temperatures drop. Instead, these insects employ various survival strategies to endure colder months, allowing them to re-emerge when conditions become favorable again. Their ability to persist through winter varies depending on the species and environmental factors.
The Biological Strategy of Diapause
The primary mechanism mosquitoes use to survive cold temperatures is a dormant, hibernation-like state known as diapause. This biological process is triggered by environmental cues, particularly decreasing daylight hours and colder temperatures, typically when temperatures fall below 50°F (10°C). During diapause, a mosquito’s metabolic activity slows significantly, allowing it to conserve energy without feeding. This pre-programmed state of suspended development enables them to withstand conditions that would otherwise be lethal. This adaptation allows many mosquito species to bridge unfavorable seasons, including cold winters.
Life Stages That Survive Winter
Mosquitoes survive winter in different life stages, depending on the species and local climate. Adult female mosquitoes of many species enter diapause, seeking sheltered locations for colder months. Male mosquitoes generally have shorter lifespans and do not survive into winter.
Many species, such as those in the Aedes genus, overwinter as hardy eggs. These diapausing eggs are laid in late fall and resist freezing and drying, remaining dormant in moist soil or near water bodies until spring rains and warmer temperatures trigger hatching. Larvae can also enter diapause, surviving in sheltered, unfrozen water or moist soil. Pupae are sensitive to cold temperatures and do not live through freezing conditions.
Common Winter Hiding Spots
Mosquitoes in their overwintering stages seek protected environments to shield themselves from extreme cold. Adult female mosquitoes in diapause often find refuge in underground spaces like burrows, storm drains, and culverts. They also use hollow logs, tree cavities, and crevices in tree bark for shelter.
Human structures also provide common hiding spots. Basements, crawl spaces, sheds, garages, and attics can become winter refuges, offering stable temperatures and protection from harsh winter elements. Overwintering eggs are found in or near water sources that may freeze or dry out, such as containers, ponds, or areas prone to flooding.
How Different Species Adapt
Not all mosquito species employ the same overwintering strategies, showcasing a diversity of adaptations. Culex species, including the common house mosquito (Culex pipiens), are known for their adult females entering diapause. These females reduce metabolic activity and seek sheltered places like underground drainage systems or cellars.
Many Aedes species, such as the Asian tiger mosquito (Aedes albopictus) and Aedes aegypti, primarily survive winter as cold-hardy eggs. These eggs are laid in dry areas or containers that fill with water later, enduring freezing temperatures until conditions suit hatching in spring. Anopheles species, which include malaria vectors, also overwinter as adult females in diapause. During this time, their blood-feeding and reproductive activities are significantly reduced. While most mosquitoes become inactive, some species, like Culiseta inornata, are active during winter and are sometimes called “snow mosquitoes.”