The recent flooding over much of the United States could potentially spell a worse than usual mosquito population. As rivers and streams recede, they leave behind ponds and puddles where mosquitoes can breed. Even worse, some mosquito species live only in flood zones.
The Mosquito Life Cycle
It helps to first understand the life cycle of mosquitoes. All species go through a process of metamorphosis that consists of four stages:
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- Eggs. Depending on the species, eggs are laid singly or in “rafts,” and they usually float on the surface of water.
- Larvae. Larvae (“wrigglers”) emerge from the eggs and have an entirely aquatic existence. Most feed by filtering small organisms from the water. Each larva grows by molting its exoskeleton, doing so four times in four to fourteen days, depending on species and water temperature.
- Pupae. The fifth molt results in the pupa (“tumbler”) stage. Pupae represent the transitional stage between larva and adult. This active stage is also aquatic and is able to dive from the surface when disturbed.
- Adults. The adult mosquito emerges from the pupa stage at the water’s surface. The surface tension of the water allows the tiny insect to rest there until its body hardens and its wings dry for flight.
Different Lifestyles
Permanent Water Mosquitoes
Most mosquitoes in urban areas are permanent water species that breed in standing water that collects in tree holes, bird baths, cans, and other containers, as well as on tarps and in neglected or abandoned swimming pools and puddles. Additional sources of standing water, as floods often leave behind, provide these mosquitoes with additional places to lay their eggs.
Floodwater Mosquitoes
Floodwater mosquitoes, such as the Inland Floodwater Mosquito, Aedes vexans, lay eggs in dry locations where there is a high probability of flooding. Their eggs require a period of drying out, and the eggs can survive at least a year without water to trigger hatching.
Floodwater mosquitoes are most abundant around the edges of moist pastures, irrigation furrows, swales, ditches, and similar habitats. When flooding occurs, the water triggers the eggs to hatch, which is why you may see increases in mosquito populations after flooding. The adult females can then fly several miles to find a meal of blood.
How to Cope
To fight permanent water species, make sure to eliminate all rain-catching containers like flower pots and tires to reduce mosquito breeding sites. Don’t forget the birdbath and pool cover. Report neglected swimming pools. Get proper inoculations before traveling abroad.
There is little you can do to curb populations of floodwater mosquitoes, so your best bet is to use repellents and do your best to avoid areas mosquitoes are likely to be dense. Apply products with DEET as the active ingredient, such as Ben’s® 30% DEET. Read the directions and warnings carefully to ensure maximum protection. While the Inland Floodwater mosquito does not transmit West Nile Virus, it can carry Eastern Equine Encephalitis.
Did You Know?
Although this year’s wet winter, spring, and flooding across North America has raised concerns about the potential for more mosquitoes, and more cases of the diseases they spread, the news isn’t all bad.
In California, at least, severe cases of West Nile Virus are more common in drought years. Why this is so remains open to speculation. Birds are the host for the virus. Humans contract it only when bitten by a mosquito that has previously fed on an infected bird. Perhaps drought forces birds and mosquitoes into closer proximity at dwindling water reservoirs. Whatever the case, the end of the drought in California may signal a decrease in West Nile Virus cases in the state this year.