April Showers, May Flowers and Mosquito Blood Banks
EDITOR'S NOTE: This column is a rerun from April 24, 1997.
April showers bring May flowers - or so the old saying goes. But there is a downside to those spring rainfalls. They are also partially responsible for the summer's mosquito crop.
Those night-flying, blood-thirsty mosquitoes live as immatures in standing water. So rains that provide water to nourish the spring blossoms also fill potholes and low-lying areas in woods and back yards that become breeding sites for mosquitoes.
There are lots of different kinds of mosquitoes. More than 100 species live in the United States. They occur from Alaska to the Gulf Coast states; they thrive from the marshes of the eastern part of this country to the deserts of Arizona. And all of them have at least two things in common: Female mosquitoes need a blood meal to produce eggs, and their immatures live in water.
As a general rule, the female mosquito lays her eggs during May and June. She lays them one at a time or in groups of 100 to 400 on the surface of the water. In one to three days, the eggs hatch into what is called a wriggler. The wriggler gets its name from the motion it makes as it moves through the water.
Wriggler mosquitoes do not get oxygen from the water as do other insects that live in the water. Rather, they are air breathers. They get air through a miniature snorkel, a siphon, that is attached to the rear end of the insect. The wriggler breathes by coming to the surface and sticking its snorkel through the surface of the water. The fact that the wriggler has to get air from the surface lead to a method of control in which the water surface is covered with a film of oil. The oil prevented the young mosquito from getting air, and it suffocated.
Mosquito wrigglers feed on microscopic plants, and in a week to 10 days they molt into the pupal stage. In this stage, they are shaped like commas and stay near the surface of the water with breathing tube in contact with the air. When disturbed, they will leave the surface in a sort of tumbling motion and are sometimes called tumblers.
In two to three days the tumbler becomes an adult mosquito. The skin of the tumbler splits down the back, and the winged adult climbs onto the skin and uses it as a float until it is ready to fly.
The newly emerged adults use their wings to continue the population of mosquitoes. The males fly off to find females, and the females, once mated, fly to find a host to supply a blood meal. That is the part of the mosquito's life cycle that most of us dislike. That is when we are asked to donate a little blood so the female mosquito can produce another generation of eggs. Most of us would just as soon not contribute, but the mosquito doesn't ask. She just helps herself!