Master Naturalists: Mosquito season in the Coastal Bend
By Paul and Mary Meredith
June 21, 2012 at 1:21 a.m.
While our daughter and son-in-law were in last week, he went outside to try out a new camera lens on the wildlife. Well, he found wildlife, lots of it, mostly mosquitos. He came back inside fast. It is mosquito season, and we have had enough rain recently to provide excellent breeding conditions. He ran into a day-feeder species, Asian Tiger mosquitos, an invasive urban species first identified in Houston in 1985.
Mosquito facts to consider
More than 3,500 species of mosquitoes exist worldwide, with 65 species in the U.S. Their name comes from Spanish and Portuguese, and means "little fly."
Mosquitoes are true flies (Order Diptera), with four wings, even if the hind wings are stunted. Taxonomists use a whole bunch of different body characteristics to classify them, but it is easiest to group mosquitoes by where females lay eggs: in permanent pools, transient water, floodwater, and tree-holes (as well as artificial containers).
It's not correct to say that mosquitoes feed on blood; they actually feed on carbohydrates like flower nectar and sweet saps, sometimes even on available hummingbird feeders. The blood their piercing mouth parts extract supplies essential proteins to build eggs. Thus, only females bite.
What to look for, control in your yard
Mosquitoes that lay their eggs in permanent water, ponds, creeks, etc.. Eggs hatch in 48 hours or less. Their larvae mature in five to seven days. Eggs are laid daily, so numbers are fairly constant, barring drought. This is typical of species that breed in artificial containers (tires, bird baths, buckets and cans, clogged gutters, etc.).
These species usually fly five miles or less. If you see them, including the Asian Tiger, you may have a breeding ground nearby that you can control. Dump standing water and treat water with Bacillus thuringiensis israelensis toxin (BTi), which comes in donut-shaped tablets. Check with your nurseryman for BTi, or you can order it online.
Floodwater mosquitoes are like time bombs, laying their eggs on dry ground, in depressions and low areas that will hold water after a rain or high tide. They may remain dormant for years and, when temperatures are finally right, hatch in moments after a rain or flood event submerges them. Adults emerge in five to seven days.
Because all the eggs hatch simultaneously, millions of adults suddenly appear, like an explosion, with no warning. No mosquitoes on one day, and the next day, they are everywhere. The bad news is these species may fly as far as 100 miles looking for a blood host.
There is no control for these species, which are attracted to city lights other than municipal-area-spraying and waiting for them to die off. Salt marshes and rice fields are their preferred breeding areas, although they will produce in a cow's footprint or feral hog wallow if it holds water for five days.
A final caution
If you see small, nondescript brown mosquitoes and are bitten only at night, you are probably seeing Culex mosquitoes. They can be bad news. They breed in standing water high in organic matter like underground storm sewers and in water standing under houses built on piers.
One Culex species can transmit St. Louis Encephalitis, a dangerous viral disease. If the critter bites a bird infected with the encephalitis virus and then bites a human, it can pass on the virus carried in its gut. You can help by eliminating water standing around or under the home, use repellents, and spend less time outside after dark.
Sources: Jefferson County Mosquito Control; J.A. Jackman and J. K. Olson* B-6119 6-02, The Skeeter Squad; Center for Disease Control (CDC) Mosquito ID site at UT El Paso; Vector Control Presentation EM Conf 2012 (ppt), Texas Department of State Health Services
Paul and Mary Meredith are master naturalists. Contact them at email@example.com.