Multnomah County is home to 26 different species of mosquitoes, 9 of which are considered vectors, meaning they can spread disease to humans. Mosquitoes have a four stage life-cycle:
- Eggs. Mosquitoes can lay hundreds of eggs in their life. These eggs are bound together in “rafts” or laid individually depending on the species.
- Larva. Larva or “wrigglers” are found in the water. Some float on the surface and some swim below using “breathing tubes” to get air. Larvae are busy feeding on organic material found in the water
- Pupa. Pupae are less active than larvae and are transforming into flying adults.
- Adult. These are the mosquitoes we know and see in our daily lives.
Most of the mosquitoes in our area fall into one of two categories:
- Container breeding mosquitoes. These opportunistic mosquitoes can be found throughout the county in natural and man-made containers of water. Think treehole in the woods or old tire in the backyard. Culex Pipiens and Ochlerotatus Japonicus are two of the container breeding mosquitoes here in Multnomah County.
- Floodwater mosquitoes. These mosquitoes lay their eggs on the ground near bodies of water that flood, usually in the spring time. When the water rises the eggs float on the surface until they hatch into mosquito larvae. Some areas in Multnomah County known to have large populations of floodwater mosquitoes include Government Island, Oaks Bottom Wildlife Refuge and Smith and Bybee Lakes. Aedes Vexans and Ochlerotatus sticticus are two of the floodwater species found in Multnomah County.
Some species of mosquitoes are able to transmit diseases to humans. Female mosquitoes feed on the blood of humans and other animals as a way to get necessary nutrients - we know this as getting a “mosquito bite.” If a mosquito is infected with a disease like West Nile virus, there is a potential that they spread that disease to the animals they feed on.
To reduce the number of mosquitoes around your home and neighborhood, you should eliminate the places where mosquitoes breed. Mosquitoes reproduce by laying eggs on standing water and they can develop in any standing water that lasts more than four days. Even a small bucket with standing water can become home to up to 1,000 mosquitoes. Reducing mosquitoes at home:
- Keep all buckets and cans of water empty and change the water in wading pools every other day.
- Keep swimming pools maintained by proper chlorination and working equipment.
- Keep rain gutters cleared of debris.
- Keep vegetation in and around ornamental ponds thinned.
- Consider adding a water feature to your pond since immature mosquitoes cannot breathe in moving water.
Learn more about preventing mosquitoes at home.