"Believe it or not, the mosquitoes are out there, even in winter. They're just hiding so we don't notice them. Absent unseasonably warm weather, mosquitoes remain inactive through the winter months.
Some mosquitoes lay winter hardy eggs which lie dormant in the soil until spring. In late summer or fall, the female mosquito lays her eggs singly in areas where the ground is moist. The eggs hatch when conditions become favorable again, usually in the spring when temperatures begin to rise and sufficient rain falls.
Certain mosquitoes can survive winter in the larval stage. All mosquito larvae require water, even in winter. As the water temperature drops, it induces a state of diapause in the mosquito larvae, suspending further development and slowing metabolism. Development resumes when the water warms again.
Many mosquito species live through the winter as adults. In fall, the mosquitoes mate and the males die. Only females spend the cold months hidden in protected places, such as hollow logs or animal burrows. When warm weather returns, the females must first find a bloodmeal to develop her eggs. Just when you're outside enjoying the spring weather, the newly awakened mosquito moms are out in force, looking for blood. Once they've fed, the female mosquitoes lay their eggs in whatever standing water they can find."