Mosquitoes are cold-blooded insects that do not thrive in chilly conditions. Their activity levels are directly influenced by ambient temperatures, meaning they do not “like” the cold. While their presence diminishes as temperatures drop, mosquitoes have developed various strategies to persist through winter.
Cold’s Immediate Impact on Mosquito Behavior
Mosquitoes are ectothermic; as temperatures cool, their metabolic processes slow. Below 50°F (10°C), adult mosquitoes become lethargic, cease flight and blood-seeking.
Their peak activity occurs around 80°F (26°C). As temperatures move away from this optimal range, mosquito activity, including biting frequency and reproductive rates, decreases. This direct link between temperature and their bodily functions explains why mosquitoes are less bothersome in cooler weather.
Mosquito Survival in Winter
When temperatures drop significantly, most adult mosquitoes perish, especially below 32°F (0°C). However, many species possess survival mechanisms to endure winter. One common strategy is diapause, a state of arrested development similar to hibernation. During diapause, a mosquito’s metabolism slows drastically, conserving energy.
Female mosquitoes, having mated in the fall, seek sheltered locations like hollow logs, animal burrows, basements, garages, or storm drains to overwinter. They emerge in spring, fertilized and ready to lay eggs after a blood meal. Some species also enter diapause in their larval stages, buried in mud or water beneath ice.
Another survival method involves cold-hardy eggs. Many species lay specialized eggs in late summer or fall that are resilient to freezing temperatures. These eggs remain dormant, sometimes submerged under ice, hatching when warmer temperatures and standing water return in spring.
Varying Cold Tolerance Among Mosquito Species
Not all mosquito species respond to cold in the same manner, reflecting diverse adaptations. For instance, Culex species, such as the common house mosquito, frequently overwinter as diapausing adult females in sheltered locations. These females have often mated before entering diapause, allowing for rapid egg-laying once spring arrives.
In contrast, Aedes species, including the Asian tiger mosquito (Aedes albopictus) and the yellow fever mosquito (Aedes aegypti), primarily survive winter as cold-hardy eggs. These eggs are laid in locations that may dry out but become inundated with water in spring, triggering their hatch. While tropical Aedes aegypti typically rely on eggs for winter survival, some populations exhibit a capacity for cold acclimation, enabling them to expand into cooler regions.