Separating mosquito facts from fiction


June 2, 2021

The Asian tiger mosquito is a container breeder that never flies very far from home. PHOTO: MARK SHEPERDIGIAN

The Asian tiger mosquito is a container breeder that never flies very far from home. PHOTO: MARK SHEPERDIGIAN

The mosquitoes are really big this year! The mosquitoes are out early this year! A wet spring means a bad year for mosquitoes!

All these statements are wrong for the same reason: Mosquitoes generally look alike, but their habits are quite different.

There are hundreds of species of mosquitoes in North America, but only a few dozen show up as common pests. These common pest species differ in many ways. Some breed in permanent waters, like ponds and swamps, whereas floodwater mosquitoes use temporary water, such as drainage ditches. Container and tree hole mosquitoes prefer smaller pools such as old tires, abandoned swimming pools or buckets. Some mosquitoes develop in clean water; others require dirty water. There are daytime biters and nighttime biters, and some called crepuscular mosquitoes that bite during dusk, but all are just “mosquitoes” to the public and assumed to be the same animal.

The mosquitoes aren’t “really big this year;” that’s a different mosquito than they’re used to seeing. Mosquitoes of the same species don’t vary much in size, but different species may be small, medium or large. The Eastern United States gets to see gallinippers (Psorophora ciliata), which are immense, as mosquitoes go. Upon encountering their first gallinipper on the veranda, the average customer will leap to his feet, utter the shortest possible prayer, and grab his phone wide-eyed to call you for an emergency visit. These mosquitoes can travel great distances and, if the source isn’t nearby, your customers may not see very many at all.

Mark Sheperdigian

When people say the mosquitoes are “out early this year,” they are usually seeing one of the snow melt or spring floodwater mosquitoes such as Ochlerotatus communis. These mosquitoes come out for a few weeks when snow melt or early rains result in temporary pools known as “vernal pools.” They bite throughout their adult life of up to several weeks, but they develop slowly in the cold water and typically have only one generation per year. They lay their eggs on the dried pool beds, but they won’t hatch until next year when the next vernal pool forms. A dry spring may cause the eggs to skip it and wait another year. They’re not “early”; they’re right on time.

A wet spring does not mean a bad year for mosquitoes. People are confusing the arrival of spring floodwater mosquitoes with the common species that bite throughout the summer. Summer floodwater mosquitoes and container breeders need heavy rains to fill their breeding sites and trigger their appearance. A few species, such as the Asian tiger mosquito (A. albopictus) are container breeders and ferocious biters, but they don’t travel far from home. Populations vary greatly from year to year based on the available breeding sites. A wet spring may get them started, but they won’t continue for long if the rains cease. If the summer is marked by heavy rains every week or two, of course, it may indeed be a bad year for mosquitoes. But spring rains are no predictor of this.

Identifying mosquitoes isn’t difficult. It just takes a little diligent study and practice. Once you know which mosquitoes are active, you can identify their habits. Take note of their typical sources, flight ranges and periods of activity to help you devise the best control strategies.

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