Summer's Bloodsuckers

By HENDRIK HERTZBERG GAINESVILLE

It is your trump,

It is your hateful little trump,

You pointed fiend,

Which shakes my sudden blood to hatred of you:

It is your small, high, hateful bugle in my ear.

Why do you do it?

Surely it is bad policy.

They say you can't help it.

-- D.H. Lawrence, The Mosquito

Sometime this summer -- it's probably already happened -- you will hear that hateful little trump. At the first sound of its intensely annoying whiny hum, faint but frantically high-pitched, you'll hold stock-still, on full alert, hand raised at the ready. And then: splat. One less mosquito to trouble the peace of man and beast.

As you brush aside the spindly corpse, the poet's question may occur to you. Why do mosquitoes make that irritating little noise? Its usefulness from the human point of view is obvious. But what is its survival value from the mosquito point of view? Why in the world would these otherwise canny creatures go to the trouble of evolving a behavior so ideally suited to helping their prey find and swat them?

A good place to ponder this puzzle -- or to find out anything else you ever wanted to know about mosquitoes -- is an innocuous-looking brick building near the University of Florida's Gainesville campus. Its halls nourish, among other obscure yet useful twigs of the mighty oak that is the U.S. government, the Mosquito Unit, or, as it is formally known, the Mosquito and Fly Research Unit at the Medical and Veterinary Entomology Research Laboratory of the Agricultural Research Service of the U.S. Department of Agriculture.

This bastion of research in the battle against bugs has never been more important. A new enemy has appeared in the form of the Asian tiger mosquito, a variety that was accidentally imported from Japan in 1985 and has since spread to 21 states, mostly in the Southeast. Government scientists announced last month that a group of these mosquitoes in Florida had been found to be carrying the virus for Eastern equine encephalitis, a rare but often fatal brain disease. Only 11 Floridians have caught this disease, and health officials see no reason for panic, but mosquito control has taken on a new urgency.

Gainesville's Mosquito Unit, along with everybody else involved in what is anthropocentrically called pest control, is rethinking its philosophy and strategy. The mosquitoes are the same, crafty and cunning as ever. But the weapons and tactics used to combat them are changing fast. Chemicals are out; biologicals are in. Dumping poisons indiscriminately is no longer in vogue; figuring out ecologically correct ways to get mosquitoes to do themselves in is all the rage. "The era of insecticides is coming to an end," says Donald Barnard, the Mosquito Unit's chief. "They're still our first line of defense. But the bugs adapt very quickly to whatever we throw at them. The emphasis now is on outsmarting them, and to do that you have to understand their behavior."

Very well: Why do mosquitoes whine? For many species, the unit's two dozen scientists and technicians will answer in one voice, and in one word: sex.

A mosquito, it seems, is essentially a tiny winged speck of libido. Here's what typically happens: the males form a hovering globular swarm, ranging from a softball-size band of a dozen to a ballroom-size throng of millions. To any female that may be around, the male buzzing sound is like a neon sign in front of a singles bar. She makes a beeline -- all right, a mosquitoline -- straight into the swarm. Once she's inside, the sound of her wings, beating 250 to 500 times a second, becomes the mosquito equivalent of a flirty hair flip. The males frantically elbow each other to get at her, and within seconds one of them scores. The pair, copulating in midair, float down in crazy circles, coming briefly to rest in a tangle of legs and antennae. Who cares if that hum might later cost them their lives? It was worth it.

Among mosquitoes, by the way, the "woman above" position is mandatory. Their sexual organs are weirdly like ours, with vaginas, ovaries, penises and testes. Their coupling takes four to 40 seconds, though in a few of the 2,500 known species male and female may remain locked together for more than an hour. They show every sign of ecstasy, but do they feel it? Mosquito Unit head Barnard looks pained. This is not the sort of question sober scientists are supposed to concern themselves with, and besides, there's nothing in the literature about it. "Well," he finally admits with a sigh, "they do have a central nervous system."

The sex had better be good, because in most mosquito species that have been studied it's strictly a one-night stand. The female has no further need of her partner or any other male for the rest of her life. She stores the sperm from her sole encounter in special sacs, fertilizing her own eggs every time she lays a batch, whether that is once or a dozen times.

From this point on, in any case, sex no longer rules her life; violence does -- and this is where we come in. To nourish and develop her eggs, she needs what entomologists call, with admirable directness, a "blood meal" -- and she needs a new one for every batch of eggs she lays. Every mosquito bite in the history of life on earth has been inflicted by a female. This is science, not misogyny.

When a blood-hungry mosquito lands on a human forearm -- or, more likely, on the eyelid of a cow, the haunch of a squirrel, the wing of a roosting bird or even the back of a caterpillar -- she goes to work with awesome efficiency. Her slender proboscis, consisting of two sharp and sometimes serrated cutting % tools surrounding a pair of tiny tubes, pierces the skin (and, if necessary, the cloth or feathers protecting it) and finds a capillary, bending to slide into the tiny blood vessel. Down one tube comes her saliva, which deadens sensation and blocks coagulation. Up the other goes a drop of her victim's blood. In less than a minute, she makes her getaway. She finds a place to rest and digest her vampire's repast, while her victim is left to scratch the welt that soon forms in allergic reaction to her ghoulish drool.

The eggs she will lay a few days later -- from half a dozen to upwards of 300, depending on her species and the richness of her blood meal -- turn into larvae, which lead a complete aquatic life of their own and are as different from flying mosquitoes as seals are from buzzards. Not much water is needed: a tablespoon in an old beer can or tire casing is enough to provide a home for 200 of these little air-breathing water worms, but the more water the better. The larvae zip around, feeding on bacteria and bits of vegetation, which they filter through bristles in their mouths. In some species they also eat one another or the larvae of other mosquitoes, a habit the folks at the Mosquito Unit would like to encourage.

After a set time -- from less than a week to several months, depending on the species -- the larva suddenly stops eating, curls up into a comma and becomes what is called a pupa. Over the next few days, it transforms itself like some buggy version of Terminator 2. Its nerves and muscles melt and reform with astonishing speed until the new adult mosquito sloughs the pupal skin, emerges at the surface and takes off. If one thinks of the humble, fishy mosquito larva as a distinct animal in its own right, then it is one of God's creatures for which resurrection and afterlife are scientific facts. Instead of dying, it sprouts wings and ascends into the heavens.

Once airborne, the mosquito becomes a flying machine that puts state-of-the- art aeronautics to shame. Mosquitoes have range: though most live out their lives within a radius of a kilometer or two, some swamp species have been known to fly more than 160 km (100 miles). And they have maneuverability: a mosquito flying through a rainstorm can land safe and dry on the nape of your neck after dodging hundreds of drops that to it are as big as falling refrigerators.

All this makes the mosquito a formidable adversary, one that has caused no end of trouble for human beings. Malarial mosquitoes, some historians think, contributed to the fall of ancient Greece. Europeans of medieval times were tormented by the insect Chaucer knew as the midge; the English word mosquito, from the Spanish for "little fly," appeared in the 16th century, along with new and nastier New World species. In the 1880s the Frenchman Ferdinand de Lesseps, fresh from the triumph of building the Suez Canal, was utterly vanquished in his heroic effort to dig a canal across the Isthmus of Panama, partly because thousands of the Europeans he brought with him fell victim to mosquito-borne disease.

With the deployment of DDT in 1939, it looked as if final victory over the mosquito might be at hand; and indeed, through the years chemical insecticides took such a toll on mosquito populations that yellow fever and other infections they carried became almost unheard-of in the developed world.

Chemicals also took a toll on mosquito research. "The age of DDT was also the dark age of entomology," says Dan Kline, another of the Mosquito Unit's scientists. "There was no money for basic research. Mosquitoes a problem? Just take some DDT and nuke 'em. Why bother with research when you can do that?"

The quest for new methods of mosquito control has turned the dark age into something of a golden age. Government scientists such as Barnard and Kline now have strong arguments for spending less of their time testing bug-killing chemicals and more of it trying to understand the way mosquitoes behave and how they fit into the great chain of being.

This change reflects more than the growing reluctance to put powerful poisons into the environment, where they can make their way into human and animal tissues. Insecticides are fearsome engines of natural selection. A dose of strong insecticide will kill every mosquito it touches -- every one, that is, except those that are immune because of some genetic quirk. The resistant bugs, left alive to reproduce themselves, eventually come to dominate the species. Chemical insecticides are great at suppressing bug populations in the short run, but over time they are just a particularly efficient method of breeding tougher, hardier insects.

Seeing the ultimate futility of spraying chemicals all over the landscape, pest controllers are looking at ways to lure mosquitoes into traps that poison the bugs without contaminating the whole environment. One idea is to copy the buzzing sound of the mosquito's sexual come-on. Another technique is to % discover and duplicate the chemical odors that attract mosquitoes to animals. Possible bait: octonol, a compound in cow's breath. A third set of strategies turns on the attractant qualities of heat, which mosquitoes like. (If your hot-blooded spouse wakes up covered with bites and you don't, his or her slightly higher body temperature may be to blame.)

A better way to conquer mosquitoes may be to enlist their natural enemies. The Mosquito Unit's experts think bug populations could be infected with -- and decimated by -- a variety of microbes, including protozoans and fungi. Entomologist Jimmy Becnel expects to conduct a field test of such biological warfare within a year or two.

Genetic engineering could one day be the best weapon. Scientists hope to create mutant strains of mosquitoes that do not lay eggs or at least do not nourish them in the usual bloodsucking fashion. Introducing the mutants into mosquito populations could lead to interbreeding and thus interfere with the rampant reproduction of the natural bugs.

But the battle between man and mosquito has been raging for a long time, and neither side is likely to win it soon. Despite all of man's spraying, draining, zapping and slapping, there are still an awful lot of mosquitoes in the world. Nobody knows how many, but a very rough calculation (the only kind possible) would put the total number of mosquitoes on the planet at any given moment at around 100 trillion, give or take a few dozen trillion. So you needn't feel too bad about squashing a few.