On a warmish (relatively speaking) deep winter day, there was a mosquito out and about at our house. Don’t you guys hibernate? I wondered, swatting at it. I don’t know of anyone who professes a liking for mosquitos. Well, maybe Richard Attenborough’s character in Jurassic Park. Nor do I know what useful purpose mosquitoes serve in the scheme of things. So I searched “what good are mosquitoes” and found that they do have some decent PR.

Fish eat mosquito larvae—it’s evidently a compact little package of protein—and the adult skeeters are food for bats, spiders, and birds. And, who knew, mosquitoes are quite helpful as pollinators. That’s right. Of the 3,500-4,000 species of mosquitoes (and why we need that many I haven’t a clue—can’t we replace some of those with something useful like cookie trees or vodka bushes?), only a few hundred carry the diseases such as dengue fever, malaria, Zika, and West Nile Virus that are harmful to humans. And it’s only the ladies of some species who need blood for supper. The rest of the little buggers enjoy nectar of various flavors and evidently just it around minding their own business, pollinating plants, and serving as a meal for somebody else.

There is even some research that shows mosquito saliva might be useful for treating cardiovascular disease.

That factoid alone, however, does not make me appreciate a circling, whining cloud of blood-sucking insects, so, I was pleased to discover Bacillus thuringiensis subspecies israelensis, better known as Bti. The original strains of Bt, which are naturally occurring bacterium found in soils, have been the darling of organic gardeners for years. Bt sets its sights on plant-eating caterpillars like cabbage loopers and tomato hornworms, paralyzing their digestive systems and resulting in starvation. Bti is a newer strain that produces toxins which target larvae of fungus gnats, black flies, and mosquitoes, the presence of which are a huge detractor to the enjoyment of outdoor activities. You can buy Bti in a variety of forms—granules, tablets, pellets, handy little chunks, even spray. You put the prescribed amount in standing water (obviously it is best not to have standing water, as that’s where mosquitoes like to lay eggs, but...), including flower pots, animal watering troughs, bird baths, and rain barrels. It doesn’t work instantly (most things in Nature do not), and does break down in sunlight, so the experts recommend a fresh application every seven to fourteen days. Bti is not harmful to people, pets, livestock, or honeybees.

There is one more thing you can do to dissuade at least one species of mosquito from targeting you as a source of liquid refreshment. A recent study in the journal Current Biology revealed that some the disease-carrying mosquitoes, such as the Aedes aegypti, identify their human targets by odor, and can associate our smell with unpleasant interactions for at least twenty-four hours. What’s unpleasant interaction to a mosquito? Swatting at it.