Mosquitoes – Flood Water hatch

  Flood Water Mosquito - by Alain Hogue via Accuweather

North Texas experienced heavier than normal rainfall in the late summer of 2022, saturating the soil to such a level that it triggered the hatch of a particular type of mosquito that isn't your usual "garden variety" nuisance. These were bigger and more aggressive insects than the normal pests we struggle to keep out of our houses and yards every year. They weren't there because your mosquito traps failed or you didn't put granules in the saucers under your outdoor potted plants.

Not found in the usual wet spots around the landscape, these mosquitoes were dormant in the dry soil, possibly for several years, waiting for the right conditions to flood the land, saturating it enough so they could hatch. This large mosquito, Aedes vexans, is called the "Flood Water Mosquito" that are released from the surrounding landscape where the eggs were laid the last time there was a flood or very heavy rain event.

As described by the CDC, "Immediately following a hurricane, flooding occurs. Mosquito eggs laid in the soil by floodwater mosquitoes during previous floods hatch. This results in very large populations of floodwater mosquitoes. Most of these mosquitoes are considered nuisance mosquitoes." They don't tend to spread more disease, but they are larger and aggressive. So that's why yardwork in the dusk and dawn hours can be so difficult after a particularly wet episode.

  Aedes vexans by Katje Schultz, CC by 2.0 via Flicker

From a pest control site called VDCI, that specializes in these mosquitoes, comes this information: "By floodwater, it means that they lay their eggs individually on moist soil above the waterline at a wide variety of aquatic habitats, including temporary pools such as detention ponds or irrigated fields, but also permanent water bodies where the water level fluctuates. They especially prefer to lay eggs where there is a lot of leaf and twig cover, helping to keep the soil moist. After a short period of drying, the eggs must subsequently be flooded with water to hatch. During periods of drought, eggs can remain dormant but viable for many years, waiting for the water to rise."

Don't be fooled by the photo above of the flood water mosquito (Aedes vexans by Katje Schultz) resting on a flower; they are aggressive biters and go after humans and pets. For more information:

CDC: What to Do After a Hurricane or Flood

Rise in 'floodwater mosquitoes' expected in wake of historic Ida deluge (Sept. 2021)

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