Vexation: Mosquitoes

For the past two years, mosquitoes have been practically absent from the landscape on Owl Acres. The years were dry, verging on drought. This year, we’ve had a fair amount of rain. It’s caused flooding, as well as filling up ponds and streams and ditches. It’s a perfect year for the dreaded mosquito.

Mosquitoes are classified in the order diptera, the same order as flies. Like flies, they have one pair of wings, and six legs. They have three body segments—a head, thorax and abdomen, and antennae on their heads. Mosquitoes’ wings are clear with scales and hairs along the veins and edges, and their mouth looks like a long straw which they use to suck with. They’re usually about a quarter to a half inch long and fly with that super-annoying high-pitched whine. 

Male mosquitoes eat nectar, sap, and other plant juices. They don’t suck blood. Females need protein for their eggs to develop, so along with their veggies, they do suck blood. And they know just where to find it. Their acute sense of smell and sensitivity to body heat bring them right in to the best-smelling humans and animals. They particularly like the lactic acid and other compounds found in human sweat. Human breath loaded with carbon dioxide, bacteria on the skin and even blood type make some of us more attractive than others. Mosquitoes have always favored me over my companions. Should I be honored?

Generally speaking, the lifecycle of most mosquitoes follows a similar pattern. As soon as she emerges as an adult, a female mosquito will start looking for a mate and place to lay her eggs. She will lay her eggs on the surface of still water—even as little as a tablespoon of water will do. She may lay the eggs singly or in rafts floating on the water’s surface. When the eggs hatch, the larvae will hang in the water just below the surface, breathing through a tube at the tip of their abdomen like a snorkel. If alarmed, they will swim in an S pattern deeper into the pond or bird bath, earning the name wrigglers. They filter feed on tiny aquatic microorganisms near the surface. Over the next four to 14 days, depending on food and temperature, the larva will molt four times as it grows, and then pupate. The pupa doesn’t feed but still breathes at the water’s surface. If disturbed, it will roll and tumble to go deeper in the water, and is known at this stage as a tumbler. This lasts up to four days, at which point its outer skeleton splits down the middle and the adult mosquito emerges. If an egg finds itself on land instead of in water, it can happily dry out and wait to hatch until the next flood weeks or years later.

Over 3,000 species of mosquitoes inhabit the earth, and 175 or more species can be found in the United States. Entomologists routinely set up and monitor mosquito traps to determine what species of mosquitoes are plaguing us. They’ve identified 57 separate species in Iowa, with the most common species being the inland floodwater mosquito Aedes vexans.

The name comes, aptly, from the Latin for vex or annoy, and that is exactly what they do. This species doesn’t generally carry diseases, although it can carry West Nile and dog heartworm. The females prefer larger mammals like humans. Although they will bite any time of the day or night, they’re usually active about an hour after dusk—just in time to join that summer campfire. They’re black with white bands at the base of each leg and abdominal segment. These vexing critters prefer to lay their eggs one at a time just above the waterline. The eggs dry out briefly, then are rehydrated when the water level rises. That’s when they’re ready to hatch. Because it’s been so dry on Owl Acres the past couple of years, some of this year’s crop of vexers may have been waiting quite a while until conditions were favorable before they hatched.

The northern house mosquito (Culex pipiens) and its cousins Culex tarsalis are also common and adaptable visitors. They like to lay their eggs in stagnant pools of water like in old tires, bird baths and other man-made habitats. They bite during the day and are more likely to carry West Nile than the Aedes vexans.

With various species of mosquitoes lying in wait this summer, our best defense seems to be to eliminate standing water and use insect repellant. So that’s the plan. Clean the gutters and put a can of spray just outside the door for all occasions.

Photo from Wikimedia.org by Christina Butler Alt text: Aedes vexans as you don’t usually see or care about.  A little insect sips nectar at a yellow flower with spiky white petals, moving pollen about and generally being a good citizen.  Male Inland Floodwater Mosquito with his feather-like antennae, large compound eyes, crystalline wings and long, delicate legs, goes about his business, mindless of the evil machinations of the females.