Why do I have so many mosquitoes a week after it rains? This is a familiar question for anyone, anywhere in the summer. The answer is floodwater mosquitoes.
These guys, the floodwater mosquitoes, are present in just about every environment from snow melt (not a problem here in Texas) to desert areas that are prone to monsoon type rains. What is unique about this type of mosquito is that they do not lay their eggs in water; but in dry or damp areas prone to flooding. There are many species of floodwater mosquitoes, and each finds the particular place they like best, from hoof prints to grassy areas along side roads. The eggs they lay can survive on dry ground for up to seven years.
The flood water mosquitoes egg laying habits and ability to fly long distances added with Austin’s multiple years of drought have made this summer a perfect year for floodwater mosquitoes. These nasty guys can show up 20 miles from where they are hatched, and lay 200 eggs in their lifetime. Because the eggs can survive drying for long periods, there can be 0.7-1.3 million eggs per acre. After a summer rain, adult mosquitoes can emerge within six days. This means a week after heavy summer rain in Austin, particularly after a few years of drought, there can be millions of new mosquitoes flying around.
Luckily for us, most floodwater mosquitoes don’t live very long, an average of about 2 weeks. For two to three weeks after a heavy storm, there will be many more (millions more) mosquitoes. You can counteract this summer scourge. Floodwater mosquitoes feed primarily at dawn and dusk, so avoid being outdoors at that time. Dress in light colored clothes and use repellents when you are outdoors. Treating your yard for mosquitoes will also be effective, but perhaps less so than for other types of mosquitoes, simply due to the large numbers that simultaneously emerge. And remember, in a couple of weeks they will be gone…until a week after the next heavy rain.