She leans against the wall, her rear end sticking up a bit, wiry hairs vibrating on her body. She's waiting for something warm to happen by. If she were to place a personals ad, it might go something like this:
YOUR HOT BREATH DRAWS ME NEAR.
So does the smell of sweat and, sometimes, feces. My turn-ons are chickens, lizards, and rodents. Heavy-breathing humans okay, too. But my clock is ticking--I've got a few months, tops. So I'll be looking for you, all summer long.
She's a predator, one any Minnesotan would know by sight. Which is why, most of the time, she ventures out only at dusk.
Even then, they are after her. Government-trained assassins control her birth rate and kill her young. Sophisticated weapons can knock her down as she flies, or kill her when she lands. Relentless, rubber-gloved lab technicians check her and her girlfriends for disease.
Her Latin family name is Culicidae. And yes, she's a she, since only the female mosquito bites. Minnesotans call her the state bird; so do a few other states, but what do they know?
"Minnesota is always vying for number one or two in the nation in terms of mosquitoes," says Dr. Robert Novak, a past president of the American Mosquito Control Association and a world-renowned mosquito expert based at the University of Illinois. Blame winter, he says--mosquitoes breed at frenzied rates in Minnesota because they don't have much time. Or look to history: When glaciers carved out the state's 10,000 lakes, they also created smaller dips, sloughs, and ponds that made perfect breeding grounds for the mosquito.
Kurt Pennuto knows those wetlands like the back of his hand. He can spot a new mosquito larva the size of a eyelash wiggling around in a swamp; after a rainstorm he will, without fail, predict where the new broods are hatching. Pennuto eats, drinks, and sleeps mosquitoes: "There have been times," he confesses, "when I've gone to bed at night, closed my eyes, and all I've seen is mosquito larvae."
Bugs, you might say, are in Pennuto's blood: His older brother is a professor of entomology in Maine, and Pennuto recalls a childhood full of insects: "We would go out and catch lightning bugs and June bugs. We'd dig up grubs in the ground and see what they'd turn into. We'd try to raise monarch butterflies from caterpillars. Little did I know that I'd be doing this for a living."
"This" is working for the Metropolitan Mosquito Control District (MMCD), the state's only full-time mosquito-fighting agency and one of about 30 such agencies in the nation. For more than four decades, "The District," as it's known to staffers, has tracked, slapped, zapped, and sprayed metro mosquitoes for more than 40 years--and along the way it's attracted more than its share of controversy, a fact Pennuto seems to take almost personally. After all, he says with an injured look, he and his 150 colleagues have only one goal--"allowing people to enjoy their back yards."
Pennuto's quest to educate the bitten masses has even transformed him into the very thing he battles. In his closet hangs a human-sized mosquito costume, complete with a pair of Styrofoam spheres sliced in half and covered with mesh to give the effect of compound eyes. In that getup, Pennuto, on his own time, has Rollerbladed down many a parade route, served as a mascot at Jesse Ventura's inaugural party, and been chased by a giant swatter at St. Paul Saints games.
This year, though, Pennuto may not have to work too hard to promote the district's work: Because of spring's record rainfalls, mosquitoes are now hatching "from eggs that were laid five, six, seven years ago." Already there are reports of "big, thick swarms of adults that can cover people's arms and faces in the middle of the day."
On a warm spring day, Pennuto is out in his blue MMCD truck, patrolling the gravel roads north of the Cities, near where Highway 169 and I-694 intersect. It's one of those rare moments in Minnesota when there's neither snow on the ground nor mosquitoes in the air: The sun is warm, but the breeze still bites. This is the time when mosquito eggs, which have spent the winter dormant on the edges of wetlands, begin to hatch.
But they're not hatching in just any wetland--and in a metropolitan area that is home to more than 65,000 swamps, sloughs, ponds, and marshes, picking the right ones to inspect is critical. Pennuto barely takes his foot off the gas pedal as he passes a body of water about the size of a tennis court, with cattails along the edge. He rattles off the data: "Type 4.4 wetland, permanent standing water 12 inches to 3 feet deep, marginal vegetative grasses, sedges, and cattails. I'm not going to even bother going there, because there won't be mosquitoes. The other end, where it's shallow, that's where you'll find them."
The truck radio emits a nice rendition of the Johnny Mercer classic "Jeepers Creepers" as Pennuto explains the mosquito fighter's favorite metaphor: the swamp as cereal bowl. "When the milk is first poured, the mosquitoes would lay eggs on the damp area closer to the rim, just where the milk laps the bowl. But as you eat your Cheerios and the levels go down, the mosquitoes follow the milk's edge and lay their eggs on the still-damp area." The eggs cannot hatch until they become wet again. Once they do, they can turn into larvae in as few as two hours, and the larvae will grow into adult mosquitoes in just ten days. So, announces Pennuto, "There's no time to waste."
He pulls over and grabs a computer-printed map of the area. Red circles mark spots where MMCD records indicate mosquito breeding grounds. Computers have made the job easier, says Pennuto, who remembers the days when "it used to be all gut feeling and going through years and years of paperwork that would tell you which sites to treat each year."
Pennuto was pretty good at the gut-feeling part of it. He has learned to see a wetland the way mosquitoes would, to look for shallow water shaded by dense shrubs, preferably with some floating leaf litter. And while he lacks bulbous, compound eyes, Pennuto has the advantage of memory--countless trips to countless wetlands, over what amounts to hundreds of mosquito generations. "It's a gift that some people have, to remember one wetland over another," he says matter-of-factly. "I remember each site."
This time of year, Pennuto is after spring-hatching mosquitoes. Controlling them early on, he explains, is critical to keeping the year's crop of skeeters down: "There's only one hatching a year, but the adults can survive all summer, so we try to stay on them."
In all, says Pennuto, some 50 species of mosquitoes live in Minnesota, but the District focuses on the 15 kinds most likely to sting people. "There are lots of mosquitoes out there that never bite humans," he explains. "Some get their blood meals from reptiles or amphibians or chickens--birds in general."
"Blood meal" is mosquito-fighter talk for what a female mosquito will suck out of its prey, using six moving mouth parts that scissor and saw their way into the skin. One blood meal is about a drop, and, contrary to conventional wisdom, the mosquitoes don't eat it. "They generally feed on plant nectar," Pennuto explains. "They use the protein in blood to develop eggs."
Like most insects, mosquitoes are obsessed with eggs and reproduction in general. That infernal buzzing? It's a mating song: Researchers who made recordings of mosquito noises in the Forties found them "so distinctive in character that an experienced observer can not only distinguish one genus from another, but can also distinguish males from females of the same species. The noise of a single female will cause the males of the same species to burst into an answering chorus."
Mosquito sex varies from species to species, with males typically swarming before grabbing females. Some species prefer to swarm over fresh dung, others in the calm air on the leeward side of chimneys and steeples; thick swarms have prompted observers to call 911 and report a fire. Few will mate in the lab; researchers speculate that this is because copulation often occurs in flight, and the couples need ample vertical falling space. And in the mosquito version of Lolita, the male of a New Zealand species, Opifex fuscus, has been observed skimming across the water's surface, ready to mount a nubile female fresh from her pupa.
But Pennuto is interested in an earlier stage of the mosquito life cycle. His waders squeak and squish as he crosses the gravel road and wades into the wetland, bearing a long-handled scoop. He dips out a ladleful of water and inspects it closely. "Lots of larvae here," he says. "I can see five right off the bat." He wades out and proffers the sample, which to the untrained eye seems to contain nothing but water, dirt, and floating weeds.
"Look for movement," he instructs, and suddenly the little wigglers become visible; they're mostly head, but the tail shimmies around in the scoop. "Mosquito larvae don't have gills," Pennuto explains. "They need to rise to the surface of the water to breathe--there's a breather siphon on the tail, which is why their heads are down." He pulls a glass vial out of the pickup's cab, deftly pours the water in, and labels the container with the wetland's number. At day's end he'll drop this and other samples off at the MMCD lab, where staffers will identify the larvae's species and genus.
In this vial, Pennuto figures the lab won't find anything but garden-variety spring hatchers--eight of them, it looks like. He does the math. "If, according to typical averages, half of the mosquitoes grow to adulthood, that's four adults. And if half of them are females, then that's two females able to lay 250 eggs at a crack, which they will probably do three times before they die. So right here are 1,500 potential mosquitoes."
But right now those imaginary insects are trapped in a vial treated with a little bit of alcohol. A few strategic scoops dumped on the gravel road could kill tens of thousands of potential mosquitoes. It's heady stuff to the amateur--though, Pennuto points out, even 100,000 would amount to just a fraction of the mosquito population that will eventually fly from this particular wetland.
Or rather, that would fly, were it not for Pennuto. He returns to his truck and opens a plastic canister containing a yellow, granular material made from ground-up corncobs. The granules are inoculated with bacteria, called Bacillus thuringiensis israelensis or Bti, which infect the digestive systems of mosquito larvae and kill them. Pennuto fills up an apparatus that looks like an oversized flour sifter and returns to the wetland. "Fish and dragonfly larvae can eat mosquito larvae," he says as he walks, shaking the sifter to spread the corncob granules around. "But the problem with this type of wetland is that mosquitoes have figured it out. Where you find mosquitoes, you don't find predator fish or insects, because this type of wetland dries up and so they wouldn't survive here."
Predators--nature's own mosquito control--aren't as effective as legend has it, Pennuto notes: Purple martins and bats will eat mosquitoes when it's convenient, but they won't devour their weight in skeeters, as the tale goes. Dragonflies and praying mantises will eat mosquitoes, but not enough to make a significant dent.
The corncob granules won't kill all the mosquitoes either: According to MMCD studies, treating a wetland with Bti will eliminate between 78 and 89 percent of the larvae living in it. But the bacteria become ineffective in about a week, and new eggs are constantly hatching--especially as the weather gets warmer and the water comes alive with the larvae of Aedes vexans. This species, which, according to the MMCD, accounts for eight out of ten mosquitoes found on humans in Minnesota, has a shorter lifespan than its spring-hatching relative, but it makes up for that by reproducing frenetically.
Which is why Pennuto will be visiting this particular wetland regularly, all summer long--even when the swarms get thick. The MMCD offers bug spray to employees, but, says Pennuto with a nonchalant shoulder shrug, "I have yet to be bothered enough to use it." It's only when he goes home to Wright County, outside the District's jurisdiction, that he faces the true wrath of the skeeter: "There have been times," he admits, "when I have had to go into the house."
Roger Moon keeps his mosquitoes in the house--or rather, in his office at the University of Minnesota, where he's served as a professor of entomology for the past 20 years. A bespectacled, fit man with a magician's quick-moving hands, he rummages rapidly through the drawers that hold the University's insect collection. It takes two minutes, tops, to find the box containing what he considers the most beautiful mosquito in Minnesota. Moon buzzes about the lab, retrieving a microscope that looks old enough to have been used for Salk's polio vaccine, adjusting a light, and offering a quick refresher course in insect handling: "You see how I'm using my pinky to hold this pin? That's the best way to hold samples," he says, gingerly placing a dried specimen of Uranotaenia sapphirina under the lens.
The mosquito is stunning indeed. Spreading out from the hairy body are a pair of wings so delicate, iridescent, and sparkling with what looks like fairy dust, they should be on a fourth grader's elf costume. But the proboscis--the mouth--is enormous, hideous. Moon puts his hands up to his face and uses his fingers to mimic its action: "You might think the proboscis would be rigid like a hypodermic needle, but it saws and wiggles around like a noodle until it finds the capillary," he explains, fingers weaving like the tentacles of a sea urchin. "And mosquitoes are quite pharmaceutically complex: Their saliva--which is what makes you itch--deadens your skin, making it less likely that they'll be slapped. The saliva also keeps your blood from clotting--otherwise it's like a milkshake that's too thick. You know..." he sucks in his cheeks as if sucking on a straw.
Then he sheds the mosquito persona and becomes the professor again. "We entomologists like to beat our chests about why insects are great," he explains. "The fact that there are so many is a measure of their success--insects make up well over half of all known species. They're small, they fly, they're fast. And they react more quickly to chemicals. One molecule of female sex pheromone can affect a male moth. We don't think vertebrates are that good at sensing a female."
Among the insect species most adept at reproduction are flies--Moon's "first love," he admits, ever since he wrote his doctoral dissertation on insects and cow pies. "Houseflies make a living exploiting the landscape--putting out lots of eggs," he explains. "The mosquito Aedes vexans does the same thing. It makes lots of eggs, spreads 'em far, and then--I'm giving it human characteristics here--prays to God for a thunderstorm."
What happens after the thunderstorm is one of the keys to insects' evolutionary success, says Moon. Some 95 percent of them go through a complete metamorphosis--eggs turn into larvae, which become pupae, from which emerge adults. "They split the environment into two habitats," Moon explains, "and so they're not fighting their kids for food." Of course, he grins, "it also means that we're fighting them on two fronts."
And we fight them, Moon explains, because we learned to over tens of thousands of years. "That fly in your chicken-noodle--before it landed in your bowl, it probably came from rotting or organic debris, road kill, results of defecation in the woods, the latrine next to the camp. Chances are pretty good that it will have bacteria on it from fecal matter. When I see the fly in my soup, I'm not saying, 'God, I'm going to get diarrhea.' But our ancestors survived better when they removed insects from their environment. At the most basic level, eliminating that fly reduces annoyance, but at a higher level, it could also extend life span."
Evolution, Moon adds, even has produced what he calls the "ish scale," a gradated reaction to various insects. "Butterflies and ladybugs go low on the ish scale--the end labeled 'not repulsive.' Anything with a stinger or a potential to bite---yellowjacket, hornets, mosquitoes--will be high on the ish scale; so will ants and houseflies. Bees might jump around the midpoint area because people like bees, but there's a fear that goes with them."
No insect registers high on the ish scale with Moon. Bedbugs? He downs the dregs of his coffee and chuckles with anticipation: "We have three bedbugs living in our office. This afternoon I'm going to prick my finger so that I can see them in action, sucking blood." Box-elder bugs? "When we moved into our house, there was a bag of box-elder seeds in the porch. It attracted bugs into our house. I was fascinated. But others in my house weren't so happy, so the bag went outside." Plagues of locusts? "In the bicentennial year, I went to Washington, D.C., when they had an overabundance of cicadas. I was in seventh heaven. These are the things we live to see. If there's an outbreak of anything, I think, Give me more. I want to see insects in the range of conditions that they can occur in."
This summer Moon will travel to Kazakhstan and Russia, looking for beneficial insects to pit against flies. "The housefly and stable fly evolved in that area; they've only been [in North America] a couple of centuries. Over there in the Old World, natural enemies have had more time to evolve. It's classic biological control: reuniting old enemies."
"Biological control" is a big word in the bug-fighting universe these days: The idea is that for each bug there's another bug that will eat it--or a scent that will lure it, or a microbe that will kill it. The Bti granules Pennuto spreads around metro-area swamps qualify as biological controls; so do the hormone-baited traps used to capture gypsy moths (see "Bugs Without Borders," p. 21). It's more expensive than the heavy-hitting insecticides that gave birth to mosquito-control districts after World War II (in the 1960s, the MMCD routinely sprayed the now-banned DDT in the Twin Cities). But for insect fans like Moon, it's the best of all possible worlds--not to mention a fascinating challenge: "The better you know a bug," he beams, "the better chance you have at finding its enemy."
If Kurt Pennuto looks at the mosquito with a hunter's admiration for his prey, and Moon studies it with a researcher's passion for detail, Mike Osterholm sees it with a mix of clinical detachment and parental anguish. Minnesota's state epidemiologist for 15 years, Osterholm is an internationally known authority on infectious diseases. He is also the father of an 18-year-old who three years ago came down with a case of LaCrosse encephalitis, one of the diseases carried by some metro-area mosquitoes.
Osterholm doesn't dwell on the illness, from which his son recovered. But he will talk, long and often, about his contention that given the right set of circumstances, mosquitoes could once again become a major health threat in the area. "Just a century ago," he notes, "malaria was a major problem in Minnesota." According to a recent report by Mayo Clinic epidemiologist L. Joseph Melton, European immigrants brought the disease with them and mosquitoes spread it around; in 1852, nearly every resident of Winona contracted it. The epidemic began to subside in the 1870s as housing and sanitation improved, the use of quinine increased, and the number of infected immigrants declined. But there were sporadic outbreaks in Minnesota until 1952, when malaria was eradicated nationwide. Visitors have kept the specter looming, however: Tens of thousands of cases were brought into the country by returning Vietnam War vets, and subsequent years have seen cases among immigrants, missionaries, migrant workers, tourists, and Peace Corps volunteers.
On the other hand, says Osterholm, "LaCrosse encephalitis outbreaks are very localized. It's spread by Aedes triseriatus, the treehole mosquito, which has trouble crossing the road from where it's hatched." Another variant of the disease, Western encephalitis, is carried by Culex tarsalis, a long-distance flyer whose range extends from the western edge of the metro area to the West Coast. In 1983, after several cases of the disease cropped up in the state, then-governor Rudy Perpich issued an emergency proclamation and sent out planes--including C-125 Air Force jets whose use had to be approved by the White House--to spray the insecticide malathion across Minnesota.
Osterholm, who served as state epidemiologist during the unprecedented effort, says he has sometimes wondered: "Was the bang worth the buck?" We have no doubt that we reduced the risk of Western encephalitis. But would we embark again on a statewide spraying?" These days, Osterholm says, he would prefer localized spraying along with public-education campaigns urging people to stay inside at night, when Culex tarsalis bites.
But encephalitis and its carriers are known entities to public-health experts, Osterholm says. Not so the Asian tiger mosquito, Aedes albopictus. The insect, native to Japan, Southeast Asia, and China, can transmit not only encephalitis, but malaria, dengue fever, and yellow fever. It often breeds inside tires, including the thousands shipped each year from Japan--where thread standards are extremely rigorous--to the United States. Asian tiger mosquitoes were first found in 1985 near Houston, Texas; by 1997 they had been documented in nearly 700 counties in 25 states. In 1992 MMCD inspectors found tiger-mosquito females near a tire-recycling facility in Savage. They've since had two more sightings, most recently in 1997 near Delano.
Osterholm, who back in the Eighties served on a tiger mosquito task force set up by the federal Centers for Disease Control, says the insect could not survive a Minnesota winter: "But they can survive over a summer here. And a disease situation could amplify quickly and become a real problem, making this mosquito much more than a mere pest or a nuisance." All it would take, he explains, is a jump in the tiger-mosquito population and a few cases of, say, malaria--a scenario that is not as far-fetched as it seems. Epidemiologists, Osterholm notes, speak of "airport-associated malaria," cases in which the victims had no known contact with the disease, but lived near an airport, where they could have been bitten by mosquitoes escaped from planes.
"We are moving tons and tons and tons of product across the world," Osterholm offers. "We are opening airplane hatches in Minneapolis that were packed for the first time in a remote tropical area of the world. In one of those planes could be a mosquito that transmits diseases we don't even know about yet."
For now, though, Minnesota mosquitoes remain largely a nuisance--and mosquito control, says UM's Moon, remains a luxury. "We are rich enough to spend money to improve the quality of leisure time. We want those tourists to come back. We want those midlevel executives to be able to golf comfortably."
But comfort is expensive. The Metropolitan Mosquito Control District's fiscal 1998 budget was $8.6 million; most of that came from a special levy on local property-tax bills, with the rest made up by state funds. And taxpayers want to see mosquitoes killed for their money.
"We got close to 4,000 calls last year," says MMCD spokesman Mike McLean. "Most are from people saying, 'The mosquitoes are
horrible at our house. Can you help us?' Or: 'We're having people over for my daughter's graduation on Saturday.' Or: 'Our block party is next week.'" This year, McLean reports, those calls have been pouring in at a record rate (20 percent more than last year), forcing the MMCD to hire an extra staffer just to answer phones.
Every time such a complaint is logged, McLean says, MMCD inspectors go out and measure the site's pest population. Studies have found, he explains, that most people notice mosquitoes after being approached by three or more in five minutes, and eleven in five minutes will send almost everyone scurrying indoors. The MMCD has set its "slap count" threshold at two mosquitoes in two minutes. Anything more will prompt the dispatching of a "fogger truck" or a worker bearing a backpack fumigating unit. Last year, some 71,000 acres were treated this way.
It's those fogging excursions that make the MMCD a favorite boogeyman for environmentalists. "Why should the government be involved in spraying for someone's graduation party?" asks Judy Bellairs, legislative director for the North Star chapter of the Sierra Club. The group has long been critical of the MMCD, and this January it was among a coalition of environmental organizations that published the Minnesota Green Scissors Report (www.me3.org/mngs), a list of budget cuts the groups said would save taxpayers money and benefit the environment. The report called for dropping all state funding for the MMCD. And in 1995 the Sierra Club supported a bill at the state Legislature that would have abolished the agency altogether.
Bellairs acknowledges that her group's opposition centers on the district's use of pesticide sprays against adult mosquitoes: The chemicals, she notes, have been found to kill fish, bees, and butterflies at certain doses, and the U.S. Environmental Protection Agency considers one of them, resmethrin, a possible human carcinogen. "Rather than spreading insecticides over thousands of acres," Bellairs argues, "it would make more sense for people to use personal mosquito sprays."
Environmentalists aren't alone with their concerns. The District's own technical advisory board has objected to the use of adult-mosquito sprays, noting that the pesticides kill only 57 percent of their targets. And this January, a legislative auditor's report faulted the district for spraying private businesses--such as drive-in theaters--at no charge, even though the district's own policies said businesses should pay.
But the biggest blow to the MMCD's image came in 1994, when the Minneapolis Park Board banned the bug-fighters from its land. Environmental Operations Manager Jeff Lee says the move came when the park board discovered that "if someone called and asked the MMCD to treat [on park land], they would do that without notifying us of any spraying. So people would call and say, 'What were you spraying in my park?' These days, Lee says, the park board allows MMCD workers to spread larval controls, but the ban on adult spraying remains in place. "You want ducks and songbirds," he says, "you need some insects to go with them."
McLean was not with the MMCD when the parks ban came down. But, he says, he's told things were different then: "From what I've heard, there probably was a certain amount of arrogance. We used to say: 'We know where the mosquitoes are, get out of our way.' I know that we weren't welcome in some quarters, and now we're slowly working our way back in. Now we bend over backward making sure that people's property boundaries are respected. Before, like a lot of government agencies, we didn't always do that good a job of listening."
Each Monday night during the summer, Pennuto and his co-workers schedule a moment of listening in their own back yards. They don't have their ears out for the voices of nagging critics, or even the hum of a fogger truck. What they're after is the siren song of lust-filled mosquitoes.
Monday night is Sweep-Net Night. Each of the 150-some employees, Pennuto explains, is offered a small net, not unlike the ones you'd use to catch butterflies, but with finer mesh. Then, "an e-mail goes out, naming the time for that week, which is one half-hour after the sun goes down, because mosquitoes are the most active just before and after sunset. So we all know that at 7:43, let's say, everyone stands still for two minutes, then swings the net around. We do that every Monday for the entire summer." It's the MMCD's way of regularly sampling adult-mosquito levels in the Twin Cities.
Gathering bugs off the clock doesn't seem unusual to most MMCD workers; lab staffers report that vacationing colleagues will often bring a sweep net and see what sort of mosquitoes are emerging up near Cass Lake or down in Pipestone. Some District employees have traveled to mosquito-hunter mecca, the pond in Israel where Bti was discovered. Conversation around the office runs toward mosquito war stories--tales from swampy parts of Alaska where the swarms can get so thick, moose are found suffocated from too many bugs up their noses; yarns about the Louisiana Gulf Coast, where, it's said, Asian tiger mosquitoes have killed calves by literally sucking them dry. And sometimes the bug hunters revel in mosquito-control fantasies. What if Jesse Ventura's daughter were getting married on the lawn of the governor's mansion, and a mandate went out to keep the dignitaries bite-free? Kurt Pennuto's face glows with excitement as he ponders the possibilities: "The things I would do: Use truck-mounted foggers to cover the open area and then spray from backpacks in wooded areas. Create a permethrin barrier by painting [the insecticide] on the tree line so that any mosquitoes that land on the vegetation fall--it disrupts their electrical system and they die."
Pennuto pauses, his eyes wandering off toward a stand of cattails. "Someday," he finally says, "instead of tromping around the county, I might have stations that mosquitoes are attracted to. Maybe giant CO2 attractors, since that's what attracts mosquitoes to humans and animals. It's done for the tsetse fly--they use cattle blood. We know that mosquitoes are attracted to dark colors, to CO2. We've made small CO2 traps using dry ice in cans painted black. A little fan sucks mosquitoes into a net. On a bigger scale, that could very well be the mosquito control of the future."
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