Where Do Mosquitoes Go During the Winter?

After summer ends and fall transitions into winter, some people might think the prime time for getting bitten by mosquitoes is over because the mosquitoes will die and no longer be a bother. They might be surprised to know mosquitoes don’t all die in the winter. To understand what happens to mosquitoes as the weather gets cold, the first step is to look at their biology.

Biological Stages 

Mosquitoes take between one and two weeks to complete their lifecycle from egg to adult, depending on temperature, and can develop in water sources as small as a teaspoon.

All mosquitoes require water to breed. Mosquito larvae develop in the water and have many tiny hairs on their mouths called palatal brushes. This is how they move water currents to comb or filter the water for algae and other organic particles to feed. Also, some larvae are predatory and feed on other mosquito larvae using sharp mouth parts called mandibles. During this stage, mosquito larvae must surface to breathe, which they accomplish through a siphon that acts like a snorkel.  

Next, the larvae will change into a pupa, or resting stage, where they do not feed. After about a week in this stage, they will hatch into adults. The adult females then seek out blood sources, where they get the protein to produce their eggs, while males only feed on plant nectar, and the cycle begins again. 

Cold Weather 

Mosquitoes are cold-blooded insects and cannot regulate their body temperature. When cold weather starts to set in, adult mosquitoes will become lethargic. When temperatures reach below 50 degrees Fahrenheit, the mosquitoes will stop flying altogether.  

Before they stop flying, adult female mosquitoes will focus on laying the last eggs before they freeze, or finding the warmest spot to overwinter. Mosquitoes tend to favor warm, sheltered areas such as underground sewer drains, sheds, garages, basements, inside logs, woodpiles and animal burrows. The mosquitoes will tend to rest on the sides of the walls of these sheltered locations.  

Mosquitoes may experience two possible stages during this period of dormancy: 

• Diapause - Blood-feeding females slow their metabolisms and remain in a paused state of development until warmer temperatures return (diapause can also occur in larval stages in some species).  
• Quiescence  - The adult female mosquito dies, but the eggs remain dormant until they’re reactivated.  They then hatch by submergence in warmer water when the temperature rises. 

Dormancy in mosquitoes is a highly complex hormonal and physiological process that is species-specific. Quiescence is an immediate response to environmental factors while diapause is a biologically controlled process that occurs before the start of adverse environmental conditions. There are five different types of diapause that different species can experience, and dormancy has the potential to occur in all life stages except the pupae. During larval diapause, part of the brain shuts down that is responsible for producing ecdysone which is the hormone responsible for regulating transitions to new life stages. In many species adult diapause is regulated in females by the halting of ovary development. There are several Aedes species where diapause occurs in the egg stage and the eggs are laid in the soil substrate along flood areas where eggs can remain dormant for as long as two years.  

Eliminating Mosquito Breeding Sources

Most mosquitoes have a short flight range anywhere from a few hundred yards up to a mile depending on the species. Eliminating standing water sources nearby is the permanent solution to solving mosquito issues. Fall and winter are good times of year to locate and eliminate these breeding sources to help prevent mosquito problems during the warmer months.  

Without water, adult mosquitoes will not have any places to lay their eggs and grow their larvae, which hatch into biting adults. Look for areas where water collects, and remove or eliminate those breeding sources. Look for and drain out water in clogged gutters, saucers under potted plants, tarps that collect rainwater, tree holes, birdbaths, corrugated downspout pipes, drip pans under window air conditioning units, and any artificial containers holding water.  

Personal Protection 

When working outdoors or in areas where mosquitoes are still active, the best protection from being bitten is to cover up. Wearing long pants and long-sleeved shirts acts as a physical barrier to protect against mosquito bites. For additional protection, clothing can be treated outdoors with commercially available permethrin products.  

Don’t forget to use an EPA-approved insect repellent on exposed skin. Be sure to read and follow all directions on the product labels before use. Remember: The label is the law.  

Resources 

Here are some additional resources to help with insects that may be “bugging” you: 

• DoD Insect Repellent System - The DoD Insect Repellent System is a safe and proven method of incorporating personal protective measures to reduce disease and annoyance associated with insects. 
• DoD Pesticide Hotline & Pesticide Use Reporting – The DoD Pesticide Hotline is a service available to answer questions about pesticide selection and use, provide help with recording and reporting pest management activities during deployments, or answer other DoD entomology-related questions. 

The Defense Health Agency-Public Health Entomology and Pest Management website and MilPEST program offers a number of useful resources and links, including an Insect ID Clinic, DoD Pesticide Hotline, Deployment Pesticide Archiving, Insecticide Resistance Surveillance and Product Testing, Vector Surveillance Data Dashboards, an EntoZoo with live insect colonies, and help with education and outreach activities.