Harvey brings Texas sized mosquito event

In Insects in the City blog

by Mike Merchant

Remember last week when I warned that mosquitoes would be hurricane Harvey’s final gift?  Well, mosquitoes are here as seen in this Facebook image, taken in Port Lavaca, TX this weekend.

The giant mosquitoes in this picture are probably in the genus Psorophora, (sore ROFF oh ruh) one of our largest, most painful and aggressive biters.  Psorophora mosquitoes have some impressive chops when it comes to survival.  One of the so-called floodwater mosquito species, they lay their eggs on land rather than water like most mosquitoes.  But not just on any land–eggs are laid at the edges of receding floodwaters, where they will re-hydrate and hatch during the next large rain event.

Because Psorophora are opportunists, taking advantage of brief rainstorms, they must have a quick lifespan.  The larvae of floodwater species like Psorophora are the speediest growers of all mosquitoes.  They need as little as 3 to 3.5 days of standing water to pass through the four molts common to mosquitoes. The pupal stage has even adapted to survive and complete its development on the mud surface of drying puddles.

What we see in this picture is evidence that floodwater mosquitoes were primed at the pump when Harvey hit the upper Gulf coast two weeks ago.  When the rains came, mosquito eggs hatched across thousands of square miles of coastal prairie and marsh, and billions of Psorophora larvae raced through childhood. Add to this that Harvey’s rainfall impacted over 400 miles of Gulf shoreline, dumping an estimated 27 trillion gallons of water. The rainfall was epic and completely unprecedented. The city of Houston doubled it’s previous all time monthly rainfall record with 39.11 inches (and Houston gets lots of rain). That’s 400 miles of Gulf coast prairies producing mosquitoes, also unprecedented, I suspect.

So don’t be surprised to read and hear lots of mosquito stories over the next couple of weeks.  If you have to be out and about in this part of Texas, there is protection you can carry. For extreme conditions a mosquito head net will be necessary. Wear light colored, tight knit, long-sleeved fabrics. T-shirts or short-sleeved shirts will not be enough.  Permethrin-impregnated shirts and pants may be worth their weight in gold.  And don’t forget to bring DEET repellent. Lots of it.

Thanks a lot, Harvey!

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