Floodwater Mosquito (Aedes vexans)

14 June

Ever the scientist, instead of squashing this guy when he landed on me and started sawing into my skin I took its portrait as I had a camera in my hand. One of the commoner mosquitoes and well named – “vexans” as in vexatious and they are certainly that. I hope you are all awed by my self control. THIS is the one you have all been waiting for.

I found an excellent description on the website of Vector Disease Control International – as follows, it’s a bit lengthy but this is very interesting:

Cosmopolitan – a species of the world, present in many countries and absent in only a few. No mosquito fits this description better than the Inland Floodwater Mosquito, Aedes vexans. They have been collected on every continent except Antarctica and South America. In most of North America this is the dominant mosquito species, becoming less abundant at higher elevations.

The name “vexans” is from the Latin word “vexāre” meaning to annoy, torment, or harass. In many parts of the world, this species is a major nuisance, the females biting in the evening, peaking in activity an hour or so after sunset. They are opportunistic feeders, taking blood meals from a variety of animals as available, but apparently preferring larger mammals, including cattle, horses, deer, and humans when present.

This is the classic “floodwater” mosquito species. 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. Extreme flooding, like the recent natural disaster in West Virginia, may wash away dormant eggs or provide water levels that welcome several new generations of Aedes vexans – only time will tell.

If the water is too cold or clear, they will not hatch. Studies have shown that a reduction in dissolved oxygen in the water stimulates hatching, such as occurs in warmer water and when the water is full of organic material like bacteria or algae. This organic matter will be food for the developing mosquito larvae. Depending on the water temperature, it takes the larva about a week after hatching to fully grow, and then it pupates and emerges as an adult a couple days later.

As mosquitoes go, these are strong fliers, being found as far as 15 miles away from their larval birthplace.This mosquito is multivoltine – able to produce several generations each season. Adults live on average three to six weeks, but sometimes as long as three months, giving them plenty of time to lay several broods of eggs, each requiring a blood meal to obtain the necessary proteins. Although considered to be primarily a biting nuisance species in most areas, Aedes vexans has also been demonstrated to be a competent vector of several diseases, including West Nile virus and dog heartworm. Rift Valley fever is also vectored by this mosquito. Although this disease is currently restricted to Africa, the widespread distribution of Aedes vexans creates a potential for Rift Valley fever to become a disease of concern globally should it spread beyond that continent.