Do Mosquitoes Prefer a Certain Blood Types?

Actually, yes! Your blood type is one of many factors that attract them

Do Mosquitoes Prefer a Certain Blood Types

Lots of different things attract mosquitoes to humans, but it’s no myth that they find some people more enticing than others. In general, mosquitoes follow odors and the carbon dioxide that we exhale. A chemist with the USDA Agricultural Research Service, Ulrich R. Bernier, reported finding over 340 unique scents that human skin gives off, and scientists are trying to narrow down which are especially attractive to mosquitoes.

The knowledge is useful because the best scents can be used as bait to lure mosquitoes away from humans, and scientists can also try to figure out how to create mosquito repellent products that disguise or minimize them to create mosquito repellent.

What blood type do mosquitoes like ?

But one of the more unusual attractants is your blood type. A few studies have shown that mosquitoes prefer people with type O blood.

As long ago as 1972, a study published in Nature magazine by Corinne Shear Wood and others showed that Anopheles gambiae mosquitoes preferred biting people with type O blood.

more recent study, published in 2004, showed the same results using a different species of mosquito, Aedes albopictus.

It’s easy to understand how mosquitoes might be attracted to different odors, but how can they tell what blood type a person is? The 2004 study also gave a clue to that.

Some people secrete sugars related to their blood type, and the study published in the July 2004 Journal of Medical Entomology divided the test subjects into groups according to whether they were secreters.

Those who were secreters in blood group O averaged 83.3% mosquito landing rates, while those who were secreters in blood group A averaged only 46.5% landing rates. After you read this article, you can answer ” why do mosquitoes bite certain people”

Mosquitoes may be able to sense the saccharides that people secrete from the skin, based on different blood types, and use that to select their preferred victims.

So if you’re blood type O, are you doomed to be a mosquito magnet? Well, not really.

There are dozens of other things that attract mosquitoes also. Some you can’t control, like exhaling carbon dioxide. Others you can, though. It’s been shown that drinking just one beer will make you more attractive to mosquitoes, according to a 2002 study in the Journal of the American Mosquito Control Association and the results were confirmed in a 2010 study. Mosquitoes also like the odor of Limburger cheese, which turns out to be similar to the odor of smelly feet. If you sweat more, mosquitoes will come to that odor too.

So even if you’re unlucky enough to have blood type O, you may still be less attractive to mosquitoes than others who lure them in different ways.

Tag : Do Mosquitoes Prefer a Certain Blood Types, what blood type do mosquitoes like, mosquitoes and blood type

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Where do Mosquitoes Go in the Cold?

Some Species Hibernate, Others Leave Eggs Until Spring.

Mosquitoes usually disappear when cold weather comes, but they don’t go away for good. They have several strategies for surviving cold weather.

Where do Mosquitoes Go in the Cold

Mosquitoes find winter hiding places along frozen stream banks and among tree roots.

Many species of mosquitoes die off when the weather turns cold, leaving only eggs which lie on the ground like seeds, waiting for warmth and spring rains to hatch and produce a new generation. Except in the warmest part of their range, these adult mosquitoes actually do only live in the summer and disappear in winter.

Other species survive cold weather by hibernating. Mosquitoes that belong to the genera Anopheles, Culex and Culiseta hibernate, and so do some other less common types in the United States.

It’s hard to believe that these fragile-looking creatures can survive freezing temperatures. J. Turner Brakeley, who owned a cranberry plantation in New Jersey, became fascinated around the turn of the 20th century with studying mosquitoes in the cold. He “tramped the bogs in sleet and rain storms in midwinter,” according to entomologist John B. Smith, collecting specimens and making observations and sending them to entomologists who cataloged and published his findings.

He discovered a new species with a unique cold-weather survival strategy, the pitcher-plant mosquito, Wyeomyia smithii, but he also found and described hundreds of ordinary hibernating adult mosquitoes, alive and well in the midst of a New Jersey winter. Smith described Brakeley’s work in the 1904 Report of the New Jersey State Agricultural Experiment Station, among other publications. The dedication of Brakeley and his contemporaries in studying mosquitoes is preserved in weird old reports still available like this.

Brakeley found Anopheles and Culex mosquitoes hiding outdoors in the sheltered areas of banks that overhung creeks, amid exposed tree roots, and in holes in the ground left by moles, mice and other animals, as well as in hollow trees.

Around human habitation, they hid in cellars of both barns and houses, where the underground temperature stayed warmer than the outside area. He also noticed them in vacant houses or buildings, or among boxes and other stored junk.

If they could find a partially heated space, such as a cellar in a heated home, they would fly away if he disturbed them. If they needed to survive where the temperature was truly cold, they went into full hibernation and he could pick them up or knock them loose so they fell to the ground.

The Hibernation Squat

To survive the cold, they took a position Brakeley called the “hibernation squat,” bending their legs and tucking their body close to the surface they sat on. They may have been trying to absorb some heat from the surface, since they’re cold blooded and can’t make their own body heat. He found thousands of mosquitoes hibernating in homes and outbuildings around the cranberry bogs, some in the cellars, others squatting on the walls or ceilings of empty buildings.

Since they don’t eat during the winter, they add weight in the fall by switching from blood to food with more sugar, such as rotting fruit or nectar, and can double their weight. Scientists have recently discovered what signals them to change their diet.

Some mosquitoes can stand the cold better than others and don’t need to hibernate where winters are mild, or will come out of hibernation when the weather warms even a little in winter, or will hatch in the spring while snow is still on the ground. They’re all usually nicknamed “snow mosquitoes,” though they belong to several different species.

Aedes communis, the snow or snowpool mosquito, lives in the northern United States at high elevations, where it uses early spring pools in otherwise snow-covered forests to raise its larvae. The adult mosquitoes don’t live over the winter, but the eggs that they lay in the fall hatch and develop into larvae so early that the new adults will be flying while snow is on the ground, even though other species may still be hibernating.

Another mosquito, Culiseta inornata, also goes by the name “snow mosquito” or “winter mosquito,” though its life cycle is different. It hibernates as an adult in the northern United States, but will stay active all winter in the south where the temperature is not as cold. Other species of mosquitoes that hibernate, like Anopheles freeborni, also come out on warm winter days.

Winter Eggs and Frozen Larvae

Most Anopheles mosquitoes hibernate, but a few, like Anopheles walkeri, lay “summer eggs” which hatch in the summer, and larger, insulated, “winter eggs” which can survive the cold. The winter eggs, which they lay only in the fall, survive freezing temperatures and lie dormant until spring, when they hatch at the coming of warm weather.

A few mosquitoes hatch in the fall and hibernate as larvae, seeking the muddy bottoms of pools to protect themselves from freezing.

The most unusual cold-weather survival strategy belongs to the pitcher plant mosquito, Wyeomyia smithii, which spends the winter frozen in the ice trapped in the leaves of the pitcher plant. These mosquitoes are also one of the few who don’t bite either humans or animals.

J. Turner Brakeley, who first discovered them, noticed the larvae frozen in solid ice inside the leaves of the pitcher plants, after the temperature had been two degrees below zero. He brought them indoors and let the water melt. Soon, they begin to move. He reported: “When the ice had all melted and the debris had settled, the larvae became busily engaged in feeding.”

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Why Mosquitoes Buzz in Your Ears

They’re actually singing mating songs for each other

Why do mosquitoes buzz in your ears? The short answer: They can’t help it. Mosquitoes’ wings make that annoying buzz or whining sound whenever they fly. When they circle your head, looking for a place to land and bite, their buzz sounds louder whenever they’re close to your ear.

Why Mosquitoes Buzz in Your Ears

Both male and female mosquitoes buzz, since they both have wings, but you probably won’t notice the whine of the males, because they don’t want to drink your blood. So they stay away from your ears, eating nectar, while the females come near to annoy you.

Scientists have discovered that the buzz of mosquitoes is more than just a way to annoy you. It’s actually important to help them find suitable mates.

Since female mosquitoes are larger, they flap their wings slower, and males know it. They use the distinctive pitch of the females’ buzz to recognize them. Louis M. Roth, who studied yellow fever mosquitoes for the U.S. Army during World War II, noticed that males ignored females whenever the females were quietly resting, but whenever the females were flying, and therefore buzzing, the males wanted to mate with them. The males even wanted to mate with recordings of female mosquitoes or tuning forks that vibrated at the same pitch.

“A delightful African folk tale for anyone who hates the sound of mosquitoes buzzing in their ears. Kids will learn the lesson not to gossip, and they’ll enjoy looking for the little pink bird in the colorful pictures too.”

Why Mosquitoes Buzz in People Ears

Why Mosquitoes Buzz in People’s Ears. You can buy this book on Amazone.

Dr. Christopher Johnston of Baltimore, Maryland had already discovered how mosquitoes can hear, almost a hundred years before. He found that they have an organ in their antenna, which was named the Johnston organ after him. It allows them to recognize the buzz of other mosquitoes.

It took other scientists to discover exactly what made the sound. Though you hear the buzz whenever mosquitoes fly, it’s not actually caused by the wings beating against the air. There’s an organ at the base of the wings which scrapes and makes the sound when the wings move. British entomologists A. E. Shipley and Edwin Wilson published a paper describing it in 1902, which they called “On a Possible Stridulating Organ in the Mosquito.” Stridulating means to make noise, and the toothed organ they found made noise as it rubbed against itself, while the wings moved.

By the middle of the 20th Century, scientists had figured out that mosquitoes have special organs to whine or buzz as they fly, that other mosquitoes can hear the noise, and that the buzz of female mosquitoes makes males want to mate with them.

It wasn’t until more recently that researchers Gabriella Gibson and Ian Russell discovered that mosquitoes actually change their buzz to “sing” to each other before they mate. They discovered that when males and females flew nearby, they altered the pitch of their buzz to match each other, and if they matched well enough, they mated. Cornell researchers tried the same experiment with mosquitoes which carry the dangerous disease dengue, and found the same thing.

As scientists learn more about why mosquitoes buzz, they may be able to use that knowledge to help keep them from mating. Fewer mosquitoes mean fewer mosquito bites, and fewer diseases being spread. For example, in this article, researcher Lauren Cator suggests that if scientists can make sterile male mosquitoes who “sing” to females just as well as fertile males, the females will choose the sterile males, and won’t produce fertile eggs.

There are a few myths about the mosquitoes you hear buzzing near your ears. Some people say that mosquitoes which buzz, don’t bite. Well, that’s true. As long as they’re buzzing, they’re flying, so they won’t bite you. But as soon as they land, look out!

Does anybody actually enjoy the sound of mosquitoes buzzing? Apparently, teenagers do! With what scientists are learning about mosquitoes, I suppose it’s fitting that teenagers are using an electronic sound called a mosquito buzz as their mating “call.”

Cornell researchers have found out that mosquitoes not only buzz in your ears, they buzz in each others’ “ears” too, as described in the video below.

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The Future of Natural Mosquito Control

Biological products will need to be cheaper & safer to compete with the current favorite, BTI

If you want to purchase a natural control for mosquitoes, you’ll probably be sold something with Bti in it. The market is currently dominated by products containing Bacillus thuringiensis israelensis or Bti, a bacterium that targets mosquito larvae. It’s relatively easy to produce and ship, and is effective at killing larvae when placed in the water where they breed. Any future natural, biological controls will need to be better than Bti, before companies can afford to spend significant research money to develop them.

The Future of Natural Mosquito Control

Almost invisible copepods, like this highly magnified Macrocyclops albidus, may one day be used to kill mosquito larvae.

But it’s not perfect. The main problem is that it’s useless against mosquitoes that breed in a nearby swamp, a neighbor’s pond, a salt marsh, tiny hidden puddles, or other areas that are too large, impractical, inaccessible, or otherwise impossible to treat. Since Bti kills only larvae in the water, once mosquitoes are adults and flying into your backyard, you’ll need to find other ways to get rid of them, such as traps or sprays.

In the future, additional natural predators and enemies may be developed, if practical problems can be overcome. Here’s a look at what may show up next, in the biological warfare against mosquitoes.

Cyclopoid Copepods

Copepods are tiny crustaceans, less than a couple millimeters long and barely visible to the naked eye. They are natural enemies of the first and second instar (the smallest sizes) of mosquito larvae. The copepods attack and eat larvae, but can also survive on other food sources in water, so they will live for long periods even after they’ve eaten all the larvae, waiting for more to hatch.

The kind of copepods proposed for mosquito control are referred to collectively as “cyclopoid copepods.” Two kinds, Mesocyclops longisetus and Macrocyclops albidus, are the ones that behave most aggressively, destroying larvae that come near even when they don’t eat them. [1]

About 25 years ago, they were first considered as a natural predator for mosquitoes. Tests have been done by adding them to water in containers, and so far, they’ve been fairly successful.

Recent trials showed they killed mostly first instar larvae of Aedesmosquitoes, but each copepod might destroy forty larvae per day, cutting Aedes breeding by 99 to 100 percent. They were less effective with Anopheles and least effective with Culex larvae.

Recent tests in Florida with the copepod Macrocyclops albidus in the lab and in field conditions showed similar results, with almost a 90 percent reduction in larvae.

In practice, they would best be used where most of the local mosquito problem is due to Aedes breeding in known locations, such as pools or water-storage containers. There are some slight risks with introducing copepods on a large scale, which scientists are still evaluating. Copepods themselves are associated with the spread of some diseases such as cholera, but they can’t spread it unless the disease is already present in the area.

Live copepods like these are available for sale now as food for fish, but they’re not ones that eat mosquitoes. However, the right species may soon be out of the testing phase and available for commercial sale as mosquito control.

Fungi

Most insects are vulnerable to diseases caused by fungi, and several that target mosquitoes had been known of for years, but when scientists discovered Bti, other researchers became interested in looking for fungal diseases which might be a similar biological control.

The article “Entomopathogenic fungi for mosquito control: A review” summarizes research on various fungi which might be effective. According to the article, the difficulty is finding a fungus which is cheap to make and easy to apply, infects a high percentage of mosquitoes in field conditions, and stays active for several generations of larvae, while producing no harmful side effects to humans, the environment or other animals.

The three most promising kinds are Lagenidium, Coelomomyces and Culicinomyces, according to the authors. While each has some useful properties, none has all the attributes necessary to be a practical control.

Coelomomyces can kill many different kinds of mosquitoes, but is difficult to mass-produce. Culicinomyces requires high doses for control and doesn’t last in the environment.

Lagenidium shows the most promise. Laginex, a product based on it, was even commercially marketed for a while in the 1990s, but never became a success. [2] Lagenidium targets mostly Culex mosquitoes, unfortunately not as high a priority for control compared to mosquitoes that spread malaria.

The authors of the article note that malaria mosquitoes will be more difficult to control with fungi, since they can breed in small, temporary puddles of water, such as ruts and footprints, so it would be difficult to spread fungi in all the areas necessary to kill their larvae.

Nematodes

Nematodes are microscopic animals which are usually harmful, causing illness in animals, but beneficial nematodes attack only creatures we want to get rid of, such as grubs or, in this case, mosquitoes.

Nematodes have the advantage of being safe for humans and other animals, as long as they target only a few harmful species. The kind of nematodes that have been most researched for controlling mosquitoes are called mermithids. Some of them target only one species of mosquito, or only one genus, so they’re limited enough to be safe. The main problem with producing them as a commercial product is that they are difficult to keep alive during storage and transportation, which makes commercial sales impractical.

Two companies attempted to develop the nematode R. culicivorax as a commercial mosquito control in the 1980s. One result was a product with the apt name “Skeeter Doom,” but neither company succeeded in bringing a nematode-based insecticide to market that was both profitable and practical. [3]

Future research may develop a way of producing and keeping alive nematodes that target mosquitoes specifically, but practical problems still need overcome.

More Ideas

Toxorhynchites mosquitoes, whose larvae are natural predators of other mosquito larvae, have been released occasionally in an attempt to control other mosquitoes. The idea didn’t work when it was first tried in the mid-twentieth century, since the predators didn’t reproduce well, and when they did, they often weren’t at the right stage of development to kill the other larvae. Later attempts have shown more success, and there is still hope that Toxorhynchites may be useful as a predator.

You may wonder what good it does to substitute one kind of mosquito for another. Unlike most, Toxorhynchites adults don’t bite!

Other small creatures which prey on mosquito larvae are flatworms and coelenterates, but storage and distribution are a problem in developing them for commercial use. Microscopic protozoa, also, are natural pathogens of some mosquitoes, but are difficult to produce commercially. [4]

Another method being tested is creating genetically altered mosquitoes. One possibility is releasing sterile male mosquitoes into the environment, in the hopes that they would mate with females, who would then bear no offspring. Another possibility is releasing males who have been genetically altered so they only sire male mosquitoes, creating a dwindling population of females. Mosquitoes may also be developed which are resistant to being infected by malaria or dengue. In that case, there would still be as many mosquitoes, but they wouldn’t be able to transmit those diseases. [5]

As of now, all these forms of biological control each have problems preventing them from being brought to market, but they’re all possibilities in the future.

Footnotes
[1] West Nile Virus Mosquitoes in Puget Sound Stormwater Systems Sergio Camacho.
[2] Larvicides and Larviciding, University of Florida Mosquito Information Website.
[3] Potential and Future, Nematodes as Biological Control Agents: Mermithidae by James J. Petersen.
[4] Biological Controls of Pests of Medical and Veterinary Importance
[5] Medical and Veterinary Entomology, by Gary Mullen, Richard Mullen and Lance Durden. Fighting Malaria with Spermless Mosquitoes, Harvard School of Public Health.
Copepod photo by Dr. Ralf Wagner, Wikimedia Commons. Toxorhynchites photo by Acrocynus, Wikimedia Commons. Culex mosquito image from the CDC.

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Mosquito zapper racket shock bugs with a wave of your hand

Mosquito zapper racket are shaped like small tennis rackets, but they’re not just for swatting. Powered by a couple of batteries, they deliver an electric shock that’s designed to kill any mosquitoes that come in contact with the paddle. You just press the button on the handle, wave the racket against any sort of flying bug, and zap! it’s dead. Pretty nifty, huh?

Mosquito zapper racket shock bugs with a wave of your hand

racket zapper kills or stuns mosquitoes on contact

There are several models in different price ranges, but all work on the same principal. The racket has a metal mesh that’s charged by the batteries in the handle when you press the button. When the mosquitoes touches the mesh, the electrical charge does the rest. They’re designed to give you a no-chemical, no swatting method of killing any kind of flying pests.

Too good to be true? Well, they’re not perfect, but the basic idea works. I’ll discuss some of the pros and cons below.

The benefits of mosquito zapper racket

One main benefit, as you can guess, is that you don’t need to use any toxic chemicals in the air you breathe or on your skin. Also, unlike a fly swatter, they kill mosquitoes in flight, so you don’t need to wait for mosquitoes to land. That makes rackets great for tackling those annoying mosquitoes buzzing around your head or those gnats hovering in front of your face. Another benefit is that they’ll take care of any kind of mosquitoes they come in contact with, so you can use one to get rid of a mosquito, then zap the wasp that’s headed for your can of pop without switching to a different method of attack.

So are they the ultimate back-yard or campground bug solution? Well, they’re pretty useful, but mosquito racket zappers do have some negatives to take into consideration.

But keep in mind…

Don’t think of them as swatters. In fact, they’re generally made of hard, brittle plastic, rather than the flexible plastic of a fly swatter, so a good whack against a hard surface can crack them. Curb the urge to do that! If you want to get rid of a bug that has landed, scare it into the air, then wave the racket against it, or lay the racket over it and let it fly up against the racket.

Don’t think of them as kids’ toys, either. Some have a “dead” screen on either side of the electrified surface, while others don’t, but you can still get a good shock from either kind if you touch the charged surface. You have to hold the button on the handle to activate the screen, so they shouldn’t shock you if the button isn’t pressed, but some use a capacitor that may hold a charge longer. Treat them as a serious bug-killing tool, and keep them away from children and pets. There are youtube videos of folks shocking themselves on purpose and it doesn’t kill them, but it doesn’t look like a really fun thing.

Also, the electrical spark could ignite flammable fumes, so don’t use them around lighter fluid, while spraying hairspray, while pouring gas in the lawnmower, or anyplace else that you wouldn’t want an open flame.

A useful bug-killing tool

But I don’t want to sound too negative. If you get a racket that has enough charge to give a good bug-killing shock, and treat it like a serious pest-control tool rather than a fancy flyswatter, it can be a good way to kill annoying flying insects indoors or outdoors, from backyard mosquitoes to wasps to houseflies.

Executioner Pro–lots of zapping power

Executioner Pro

The Executioner Pro uses two C batteries to deliver a solid shock that’s more likely to kill mosquitoes dead the first time, compared to weaker rackets using AA batteries. The Executioner Pro is also bigger than some others, with a 10 1/2″ by 8″ head and a total 22″ long including the handle, so mosquitoes are easier to contact. If you’re looking for a small, maneuverable, lightweight racket, this isn’t it, but if you’re looking for one that has a large surface that delivers a reliable bug-killing zap, this is the one.

One main difference between this racket and others is that there are no unelectrified screens on either side of the bug-killing surface. This makes it more reliable, because bugs get zapped the instant you contact them, but you will want to avoid touching the surface when the button is pressed, or you’ll get an ouchy shock too. The button that turns on the charge turns off as soon as you stop pressing it, so that makes avoiding accidental shocks easier.

Like all racket zappers, this one isn’t made for swatting, so it will break if hit hard against a surface, but you shouldn’t need to swat, with its power. You can tell it’s ready to zap when you press the button, by the LED light that comes on and by the slight whining sound it makes, and there’s no mistaking the snap and flash when a bug touches it. Most reviews seem to indicate it’s reliable, but it does come with a one-year warranty.

The same English company also makes a smaller, lower-charged model, called just the Executioner (no “Pro” in the name), if you’re looking for something more compact with not quite so much zap to it.

Reviews:

“This is smaller than a tennis racket but really packs a punch. Satisfying zzzap and flash when it nukes a bug. You get what you pay for and I bought this to replace a cheaper model that died after a month. This one is still going strong and just feels more durable, and gives a bigger shock. The trick is not to swing too fast. A gentle motion is all it takes, and when a mosquito hits the wires, it’s dead.”

“A neighbor had the regular Executioner model and I wanted one so I bought the “pro,” not realizing it was different. Now my neighbor is jealous. This is bigger, sturdier, and really packs a whallop. Mosquitoes just get vaporized. I carry it when walking where there are pockets of mosquitoes and gnats in the evening. A wave of the hand when I walk into a cloud of them and they’re cleared out.”

“The wires aren’t protected at all, so don’t let kids play with it like a toy. Feels heavy and well made, and kills all but the biggest bugs with one zap, and a second zap finishes off the bigger ones.”

Koolatron Lentek Biteshield offers smaller zap at a budget price

Koolatron Lentek Biteshield offers smaller zap at a budget price

This racket is typical of the zappers which use two AA batteries. There’s not necessarily a loud snap and flash when a bug contacts the screen, and some folks complain that the zap isn’t strong enough to kill all bugs on the first try, so it may just stun them for a moment, leaving them to fly away in a few seconds. Otherwise, the operation is similar: press the button and wave the paddle against an insect to kill it. Don’t swat, because this racket is at least as brittle and breakable as the Executioner, and probably more so!

The Biteshield racket has a non-charged screen on either side of the charged one, which gives some protection from shocking yourself or anyone else that the paddle comes in contact with while the button is pressed, but you still definitely need to keep it away from kids and not treat it as a toy. The protective screens can also make it a bit more difficult for insects to contact the live wires too, especially larger ones like wasps, and combined with the lesser charge, the success rate of killing bugs may be lower than with the Executioner Pro. The smaller batteries make it lighter to handle, though.

A few users have complained the racket either stops operating after a short while, or arrives not working, so make sure there’s a return or exchange policy, just in case.

Reviews:

“The plastic doesn’t seem real sturdy, but for the price, it works. The screen means it doesn’t shock bigger bugs like moths, but for flies and mosquitoes, it knocks them down.”

“I was surprised how long the batteries last. It’s been half the summer and it’s still going on the original pair. Only thing I didn’t like was sometimes dead bugs get stuck in between the screen layers, but they’re not difficult to knock out. Sometimes it stuns bugs rather than killing them, and they’ll fall but if you don’t step on them, they’ll fly away. Still easier to use than a fly swatter, nice big surface area to the paddle (about ping pong size) and light weight to hold. Word of caution: even when the button isn’t pressed and the light’s off, the screen must hold a charge somehow. I got a shock accidentally leaning on the screen right after setting it down.”

“Had to tape the battery cover closed. Gnats fly right through the mesh, and even bigger insects can manage to get through without a strong enough shock to kill them. Great idea but this is a cheap product.”

“Stopped working after about three weeks.”

Tag : Mosquito zapper racket, bug zapper racket, tennis racket bug zapper, electric bug zapper racket

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Can a cell phone app repel mosquitoes?

Old unproven ultrasonic repellant emerges in a new form

Wouldn’t it be the coolest thing ever if you could download an app to your cell phone that would turn your phone into a safe, free mosquito-repelling machine? That’s what some apps are claiming. The idea sounds reasonable. The app emits a sound that only mosquitoes can hear, but mosquitoes hate it, so they stay away.

Can a cell phone app repel mosquitoes

Does an ultrasonic repellant repel or attract?

The problem is that the idea isn’t new or untested. In fact, ultrasonic repellants that claim to work on the same principal have been around for decades. Before smart phone apps, the sound was emitted from plug-in or battery-powered electronic devices. Those are still on the market too. Radio stations have even tried broadcasting the sound. So the devices have been tested numerous times, in various forms. And guess what? They fail the tests. Sometimes, they even attract more mosquitoes.

If the idea is such a failure, why didn’t such devices disappear years ago? Well, some of the manufacturers offer detailed explanations that seem as if the idea ought to work, so people are willing to give it a try, especially if the device only costs a few dollars. Also, mosquito activity is so variable, depending on weather, location, and other factors like odors of perfume or sweat, that people can attribute fewer bites to turning on the sound, when the real reason may be something else and they’d have fewer bites anyway. There’s also the possibility that some sound doesactually repel some mosquitoes, but the right combination of sound, species, season, or whatever, never occurred during the actual tests. If that’s the case, though, you may never hit upon the right combination either.

You can read reviews and decide for yourself whether the devices are actually working for those who say they do, or whether it’s coincidence, or whether they’ve stumbled on some perfect combination that has eluded testers.

Mosquitoes can hear, but…

First, let’s get one objection out of the way. Mosquitoes don’t have ears, but they can hear. If you’re worried that your speaker isn’t good enough, the sound might not be truly ultrasonic, so even an ordinary cell phone speaker can probably play it. Depending on the particular app, the sound is probably right at the edge of human hearing, so children or those with excellent ears might even be able to hear it, although adults might not. One reviewer said the “kids went crazy” when he played it in a classroom.

Ultra-sonic repellants usually make one of two claims: either it’s the noise of dragonfly wings (or sometimes bats), which frighten off mosquitoes because dragonflies and bats are mosquito predators. Or it’s the sound of a male mosquito calling for a mate, which will keep biting females away because “once a female mosquito has her eggs fertilized she will actively avoid any further contact with the male,” as this app explains.

The problem is that there’s no evidence female mosquitoes avoid males after they’ve mated. In fact, “research has shown that male mosquitoes are actually the ones attracted by the female flight sound and females normally have a very weak sensitivity for sound compared with the males.”[1] As those who’ve frequented a swampy area or pond in the daytime and been annoyed by mosquitoes while watching dragonflies darting about, “mosquitoes do not vacate an area hunted by dragonflies,” as a Rutgers entemologist noted.

Failed tests

But that doesn’t matter if the anti-mosquito apps, or other ultrasonic repellants, actually work due to some other unknown reason. The problem is that in tests, they consistently don’t.

One controlled trial tested three different frequencies from 3 to 11 kHz over eighteen nights in nine pairs of houses. No one in each pair houses knew whether the ultrasound was playing in their house, until the test was over. “A total of 7485 mosquitoes (10% Anopheles, 62% Culex, 27% Mansonia and 1% Aedes) were caught, 23 per house per night. There was no significant difference in landing rate between the houses with ultrasound device and the houses with placebo for any species of mosquito.” The authors concluded, “The ultrasound device used was not effective against mosquitoes in this strictly controlled trial.”

Another test, of frequencies between 20 and 70 kHz, put four species of mosquitoes in a flight chamber, to see if they would fly toward the source of the sound to get to a bait that imitated the smell of human breath and skin. The result? “For all species there was no significant difference between the numbers trapped when the devices were switched on or off, when all devices were tested simultaneously.”

The most surprising result came from a test in which researchers counted the number of times Aedes aegypti mosquitoes tried to bite in a test chamber, during a three-minute period, either with the ultrasonic tone on or off. “The mosquito biting rates for five sound frequencies (ranging from 9.6 kHz to 18.2 kHz) initially demonstrated a significant increase.” The biting rate decreased when the tone was turned off, and increased by about one-third again when an 11.8 kHz tone was turned back on.

Was that test just a unique reaction? Perhaps so, but the results of 15 completely different tests on the landing rates of mosquitoes done by different researchers, showed a landing rate equal or greater when the ultrasonic tone was turned on, in 12 of them.[2] Some of the difference was only a few more landings out of a hundred, not significant. But geez, you’d expect the landing rates to be significantly lower if the ultrasonic repellants worked, not the same or higher.

Back in 2001, the FTC warned manufacturers that they needed to be careful making claims about ultrasonic insect and pest repellants without evidence. If such repellants worked, you’d expect manufacturers to be adding summaries of the scientific studies that showed how effective they were, but the claims still tend to be general ones, with cautions such as the devices won’t work for all mosquitoes, or you need to experiment to find the right frequency.

Why not try?

So is buying an ultrasonic repellant worth it? I’d say no. A free app? Well, if it doesn’t place anything harmful on your phone, it won’t cost anything to try, but so far, there’s no evidence to indicate it will work. However, there are a couple of things to keep in mind. If the sound is at the range of human hearing, it might be audible–and very annoying–to babies or pets, who can’t say “Turn that darn thing off!” the way older kids could, so make sure they don’t seem upset. And also don’t assume it’s protecting babies or young children, who may not mention they’re being bitten.

A cheap, completely non-toxic, perfectly safe, non-chemical mosquito repellant would be wonderful. Cell phone apps probably aren’t the answer now, though. The closest thing that probably does exist and is proven to work, is mosquito netting, and it’s available in various forms, everything from clothing to baby stroller covers. Netting is safe, effective, and non-toxic, but still not as cool and convenient as an anti-mosquito app would be, if only ultrasonic repellants worked.

Footnotes
[1] A. Enayati, J. Hemingway and P. Garner, “Electronic Mosquito Repellents for Preventing Mosquito Bites and Malaria Infection (Review),” The Cochrane Library (3:2010), 4.
[2] Ibid., 8.

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Do Bananas Repel or Attract Mosquitoes?

Or maybe neither? Science and myth collide

You may have heard that eating bananas will attract mosquitoes to you and make you more apt to be bitten. Or maybe you’ve heard the opposite, that eating bananas, or just having bananas around, will repel mosquitoes. Both rumors are going around. The one claiming that eating bananas will make you more likely to get bitten is the more common one, it seems, and the explanation is usually that when your body processes the banana, the scent comes out on your skin and makes you more attractive to mosquitoes.

Do Bananas Repel or Attract Mosquitoes

If you eat a banana, will you attract or repel mosquitoes?

Bananas are such a tasty summertime treat and are also full of potassium that helps replace the electrolytes you lose when you sweat, so it would be a shame to have to give them up during mosquito season. Are the rumors really true?

The problem is that mosquitoes aren’t predictable. Many things may make them bite more or less–the temperature, the color clothes you’re wearing, other scents or things you’ve eaten. So people who’ve eaten bananas may sometimes report more bites, when it’s coincidentally for another reason, while others may report less bites, again, for a different reason. Usually, the way to overcome such difficulties is to perform scientific studies where the variations are controlled for, but when it comes to bananas, there doesn’t seem to be much published on the topic.

ABC News quoted Susan Paskewitz of the University of Wisconson, who has published many papers on mosquitoes and has studied home remedies as well as mosquitoes’ biology. She acknowledged the common belief that eating bananas attracts mosquitoes, but said that a study in her lab didn’t indicate it was true.

Unfortunately, I haven’t been able to track down a report of the study. The University of Wisconsin’s page on mosquito home remedies just says, “Bananas have not been tested. As of now, we don’t know whether avoiding bananas will have any effect on mosquito behavior.”

So do bananas repel?

Some people who claim that bananas repel mosquitoes say it’s because they are rich in Vitamin B6. The University of Wisconsin lab did test Vitamin B, taken as a vitamin supplement. As in similar studies, they didn’t find that test subjects who took Vitamin B were any less attractive to mosquitoes.

Oddly, people also sometimes say that eating bananas might repel mosquitoes because they contain octenol. They do, but octenol is one of the odors that attracts mosquitoes. It’s actually used as a bait for mosquito traps. If the folklore is true and bananas do make people attractive to mosquitoes, could the octenol be what entices the mosquitoes? If so, it’s found in other things too, like citrus fruit and cheese, so they aren’t the only source, and eating a diet without all the many things that contain it would be difficult.

A reason bananas might attract

If the rumors are true that mosquitoes seek out banana-eaters, another explanation might come from research that Dr. E. Y. Garcia did at the Manila University College of Medicine decades ago. He published a paper titled “Serotonin and norepinephrine: the ‘life blood’ of mosquitoes” in the June 1959 Journal of the Philippine Medical Association that showed people had higher levels of serotonin and norepinephrine metabolites in their blood after eating bananas. Mosquitoes could sense that, and because they need those chemicals too, they were more apt to bite people who had more in their blood.

That could explain why bananas make people more attractive to mosquitoes. So is the folklore true? Maybe. More studies will need to be done before scientists know for sure. But because levels of serotonin and norepinephrine rise and fall in the bloodstream for a variety of reasons, they aren’t the only factor that make some people tastier than others. Add in all the other things that attract and repel mosquitoes, and the effect of bananas may not be that great.

By the way, if you’re thinking that the serotonin from bananas will at least improve your mood, because it’s a mood-regulator in the brain, well, no. The increased serotonin stays in the bloodstream and can’t cross the blood-brain barrier to get to the brain.

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Purple Martins & Bats Will Eat Anything

Unfortunately, their reputation as mosquito predators is over-rated.

Mosquitoes have a number of natural enemies, some more useful than others to control them around human habitations. Some of the ones that you actually see out catching bugs are the least useful, specifically, when it comes to mosquitoes. Maybe purple martins and bats won’t eat anything, but their choice of bugs is large enough that mosquitoes make up only a small part of their diet.

Purple Martins

Purple martins

Purple martins eat more insects than just mosquitoes.

Purple martins have gained a reputation as natural mosquito predators, and they do eat adult mosquitoes, but they eat most other kinds of flying bugs, too. No research has shown that mosquitoes are more than 3 percent of their diet, according to an article in Missouri Conservationist magazine. [1] The results seem logical, since martins catch insects during the day while flying high in the sky, but mosquitoes usually fly close to the ground looking for prey to bite, and are most active after dark. Claims that these birds can eat 2000 mosquitoes a day are based on a hypothetical diet eating nothing but mosquitoes–something that no purple martin actually does. [2]

Purple martins are still good to have living nearby, since they eat lots of other insects that humans don’t want around, including garden pests like cucumber beetles and Japanese beetles. Unfortunately, they also eat some other mosquito predators like dragonflies.

You can encourage these graceful, beautiful and useful birds to live in your yard by erecting purple martin houses, and they’ll work to control insects in general, but don’t count on them solving your mosquito problem. Houses need mounted high on a pole, and can range from simple gourds to ultimate deluxe accomodations like this, but if you’re planning to try to attract these birds, ask an extension agent or read up on specifically to see what they need in your area.

Bats

Bats are sometimes also promoted as mosquito predators. They do eat mosquitoes, and since they fly at night, they’re out at the right time to catch them. The problem is that they also like a variety of food, and will eat many kinds of insects, so mosquitoes make up only a small part of their diet. Little brown bats showed only 1.8 percent mosquitoes in their fecal pellets, compared to 71 percent moths and 16.8 percent spiders, according to one study. The diet of big brown bats was mostly beetles and caddisflies. [3]

Bats prefer beetles or moths to mosquitoes

Bats prefer beetles or moths to mosquitoes.

Bats may have received an exaggerated reputation as mosquito predators, based on a 1958 study on their ability to find insects by echolocation. [4] Enclosed in a room with mosquitoes, bats could catch on average between 1 and 9.5 per minute, which other people have extrapolated into what they could catch in an hour. But a bat that could catch almost 10 mosquitoes a minute for fifteen minutes in an enclosed room would catch much less than that, out in the wild, with a variety of insects flying in the open air.

Like purple martins, though, bats do eat many insects that are annoying or harmful to humans and their gardens, so encouraging them in the neighborhood has benefits, even if it won’t significantly reduce the population of mosquitoes.

Bat houses are best placed in isolated locations, at least 12 feet above the ground, with at least 20 feet of clear space for a flight path into the house. They like to live within a quarter mile of water, so they can drink and also so there will be plenty of insects–but lack of food isn’t a problem if you want to attract them to get rid of insects!

Though you might think they prefer homes in cool dark places like caves, they actually like warm, sunny locations, so a southern exposure is best. Mounting a house on the exposed side of a barn is better than in a tree, which is shaded and makes the house accessible to raccoons and cats.

“Bats may not prey on mosquitoes specifically, but they do spend their nights eating all the bugs they can find. A bat house is good for conservation of these often-misunderstood little animals.”

The best time of year to install a bat house is in winter or early spring before they have returned from their winter migration. When they come back north in the spring, they’ll begin looking for places to occupy. One study of 28 houses showed that bats found them mounted on buildings or poles in an average of 71 to 73 days, but it took them an average of 255 days to find them mounted in trees. [5]

The University of Nebraska Extension Service recommends placing the house over ornamental plantings so pets and children are less likely to find and pick up any baby bats that fall out of the house. For more information on bat houses, see their website on Bat House Construction and Installation.

Footnotes
[1] “Purple Martin Mania” by John Miller, Missouri Conservationist, March 2006
[2] “Relationship of Purple Martins to Mosquito Control,” reprinted at Purplemartin.org. “Martins and the mosquito body count,” by Douglas Waugh, MD
[3] Integrated Mosquito Management, University of Wisconsin
[4] The Echolocation of Flying Insects by Bats, by Donald R. Griffin, Frederic A. Webster and Charles R. Michael, Biological Laboratories Harvard University, 1960, p. 4.
[5] “Reminder to Owners of Unsuccessful Bat Houses,” from Batsnorthwest.org
Purple Martin photo by Rick Kimpel, Wikimedia Commons. Bat photo courtesy of the CDC.

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Mosquitoes have natural enemies

Mosquitoes have a variety of natural predators, from bats to fish to dragonflies. Scientists have studied what eats them in the wild, in hopes of finding enemies that can be introduced to get rid of mosquito problems near where people live. Some predators eat enough to noticeably reduce the population, while others get rid of so few that one can barely tell any difference.

Bats, birds and dragonflies which kill adult mosquitoes are some of the most obvious predators, but the least effective, according to the book Medical and Veterinary Entomology.[1] Mosquitoes make up only a small part of their diet. Fish, insects and other creatures that feed on larvae are another possible form of control, though still only effective in certain circumstances. One of the most effective natural enemies is Bacillus thuringiensis israelensisor Bti, a bacterium that only targets mosquito larvae plus a few very closely related species, without affecting fish, frogs or other desirable species, including people.

Two natural predators which attack mosquito larvae in the water are mosquitofish and dragonflies:

Mosquito-eating Fish

Mosquitoes natural enemies

Gambusia fish swimming among mosquito larvae

The gambusia fish (Gambusia affinis), also called the western mosquitofish, eats mosquito larvae. These little fish are controversial because they’re aggressive, also eating the eggs, larvae and young of native fish and amphibians and competing with them for other food. They’re not always successful at controlling mosquitoes, with unpredictable results. There is also a related species, Gambusia holbrooki, the eastern mosquitofish, which is sometimes used for mosquito control too. [2] They’re tiny, grayish fish.

People have tried stocking gambusia to control mosquitoes in various areas of the United States since the early 1900s, with varying success. Due to the harm to native wildlife, mosquitofish are regulated in many states, where they may only be stocked in enclosed ponds or pools that have no outlet to streams or rivers, so the fish can’t escape into the wild. A permit may be required.

The Rutgers Center for Vector Biology reported on several tests of mosquitofish in various situations. In an unused swimming pool, they stocked 35 fish each spring, since freezing of the water’s surface caused them to die off in the winter. The fish ate all the larvae of Culex and Aedes mosquitoes, and also ate Anophelesmosquito larvae if there was no floating vegetation. If there was vegetation on the surface, such as might be found in an ornamental lily pond, the Anopheles larvae used it to hide and the gambusia fish couldn’t control them.

The Virginia Department of Game and Inland Fisheriessuggests the fish are “somewhat effective” in ponds, drainage ditches or containers, but also cautions they must not be able to escape through an outlet into other water. Gambusia may also overwhelm local native species, including dragonflies, killifishes or topminnows, which also control mosquitoes, so there may be no actual improvement in the problem, just a change from one kind of fish to another.

Gambusia are best used in isolated, artificial bodies of water with little to no surface vegetation. If you’re interested in the possibility of using them for mosquito control in your area, contact your state’s fish and game or wildlife department to find out restrictions and recommendations. In certain limited circumstances, they may work, but in others they may not work, or do more harm than good.

A mosquitofish snacks on a mosquito larva

A mosquitofish snacks on a mosquito larva

Other fish also eat mosquito larvae, so gambusia aren’t the only choice. The popular and ornamental Koi fish are too large to feed on tiny mosquito larvae, but smaller guppies, killifish or common goldfish will live alongside Koi and eat them. This article discusses other fish which also eat mosquitoes.

The larvae can live in water too shallow for even small fish to reach them, so if you want to use fish to control them, make the sides of the pond steep, so there’s little shallow water at the edges.

Dragonflies

Dragonflies are natural enemies of mosquitoes in all their stages of growth. Dragonfly larvae live in the water like mosquito larvae and feed on them, while adult dragonflies eat adult mosquitoes.

A dragonfly waits for prey

A dragonfly waits for prey

The problem is that dragonflies also eat other things. When the mosquito population starts to get low, the dragonflies will choose other prey instead, leaving fewer mosquitoes than before, but not eliminating the problem.

Dragonflies also require a habitat similar to mosquitoes, so adding standing water to attract dragonflies will attract mosquitoes as well. If an area is already free of pools and puddles, better to leave it that way and try to deal with the mosquitoes that fly in from elsewhere in some other way. Fish which eat mosquito larvae will also eat dragonfly larvae, so both fish and dragonflies may live in balance in nature, but they’ll compete with each other if you’re trying to get them both to multiply so they can overwhelm the mosquitoes.

An experiment in Yangon, Myanmar, in Asia, showed that dragonfly larvae could be introduced to successfully control mosquitoes that were breeding in large containers of drinking water. [3] But like gambusia, dragonfly larvae work best under specific conditions, such as small artificial ponds or other containers of water where there are few other insects to eat besides mosquito larvae, and no vegetation for the mosquitoes to hide in, and no competing fish or other wildlife.

In the United States, pest control experts discourage purchasing dragonflies for mosquito control, since other alternatives are more effective in most circumstances. Purchased dragonflies will probably not be local species, and introducing non-native species may cause more problems to the local ecosystem.

Footnotes
[1] Medical and Veterinary Entomology, Gary Mullen, Gary Richard Mullen, Lance Durden.
[2] Gambusia holbrooki Fact Sheet and Gambusia affinis Fact Sheet
[3] Dragonflies & Damselflies, edited by Alex Cordoba-Aguilar.
Public domain photos of gambusia courtesy of the CDC. Dragonfly photo by Aleksandar Spasic, Stockxchng.

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Methoprene stops mosquitoes from growing

Methoprene stops mosquitoes from growing,
prevents larvae from becoming adults

Safe for people, mammals, birds, not good for frogs, fish, crustaceans

Methoprene stops mosquitoes from growing

Some of the most effective biological enemies of mosquitoes that you can buy, interfere with the growth of mosquito larvae. Methoprene (sold commercially as Altosid) is one of the top two choices to purchase for adding to water. The other is a naturally found bacillus that targets mosquitoes, called Bti.

Methoprene is a growth regulator which prevents the larvae of mosquitoes and other insects from becoming adults, by imitating insects’ natural juvenile hormone. One of its common uses is in the product Altosid, which you can buy to add to water where mosquito larvae live. Because methoprene affects other insects but is safe for humans and mammals, it’s also formulated and sold for controlling a variety of other pests, from flies on cattle farms to fleas on dogs.

The World Health Organization even recommends adding methoprene to large storage containers of human drinking water, in countries plagued by mosquito-spread diseases. They consider it so safe that humans can actually drink water treated with it, based on a risk assessment in 2007.

The commercial formulation of it, Altosid, is an effective, natural control for mosquito larvae, and is useful for bird baths, animal watering troughs, cisterns and any area where mosquito live, but where fish, frogs, crayfish, and other crustaceans don’t.

The name “Altosid” is a combination of “Palo Alto,” the location of the company that created it, and “John Siddall,” head of the chemistry group who developed it, according to Carl Djerassi in his book, The Pill, Pygmy Chimps, and Degas’ Horse.

Altosid Pro-G Mosquito Larvicide uses the insect growth regulator methoprene

Altosid, containing methoprene, is a good choice to buy for treating mosquito larvae in watering troughs. Altosid Pro-G Mosquito Larvicide uses the insect growth regulator methoprene. 

In 1975, the Environmental Protection Agency first registered methoprene as a regular chemical pesticide, but later changed its classification to a biochemical pesticide. The EPA originally found its toxicity to be low and reported that it “poses little risk to people and other nontarget species, with one exception.”

That exception was an important one. The EPA stated it is “highly acutely toxic to estuarine invertebrates,” such as crayfish, shrimp and crabs. Also, for freshwater fish, it is “moderately toxic” to warm water species and “slightly toxic” to cold water species. It is also poisonous to amphibians, such as frogs, salamanders and toads. Though it degrades rapidly in sunlight, the slow-release formulas, designed to control mosquito larvae, are also the most dangerous to other invertebrates and fish in the water, since they’re active over a long period of time.

In 1996, after further studies, the EPA concluded that the actual use of methoprene as a mosquito control didn’t spread enough of it to harm other species, and recommended that the restriction “do not use in fish-bearing waters” be removed from the label, and instead, the warning should read, “this product is toxic to aquatic dipteran (mosquitoes) and chironomid (midge) larvae”–though of course its toxicity to mosquito larvae is the whole point.

Methoprene remains controversial, as it has been accused of causing frog deformities and lobster die-offs. Groups have attempted to get court orders, to stop widespread spraying of marshes. [1]

Using Altosid to kill mosquito larvae

You can see a sample label of Altosid Pro-G here, in a pdf file. It contains 1.5 percent S-methoprene.

For killing mosquito larvae, 1/2 tsp will treat 25 square feet of surface area on water that’s less than 2 feet deep, or about 100 gallons of water. It continues to release methoprene for up to 30 days after being applied, so treatment should be repeated at least once a month during mosquito season. It can be applied at any time mosquito larvae are present, or in the spring before eggs hatch. It’s a gritty powder, which you can measure out with a teaspoon, tablespoon or cup measure (there’s a chart showing how much to use for different areas) and sprinkle over the surface of the water.

Mosquito larvae treated with Altosid, which contains methoprene, will never turn into adults

Mosquito larvae treated with Altosid, which contains methoprene, will never turn into adults

Don’t be disappointed if the larvae are still happily wriggling the next day! Altosid doesn’t work by killing them directly, so they continue to live as larvae until they’re eaten by predators or die naturally, but after their water is treated, they’ll never turn into adult mosquitoes.

The EPA’s current fact sheet on methoprene is available here. The Altosid label recommends the usual precautious of wearing long clothing and gloves and avoiding getting the product on your skin or in your eyes.

If the area you need to treat is free from fish, frogs or crustaceans, Altosid is an excellent choice. Just sprinkle it over the area once a month during mosquito season to prevent larvae from turning into biting adults.

If you want to treat a fish pond, natural wetlands, or similar areas where a variety of species live, and you want to avoid any chance of harming other wildlife, another natural biological treatment, Bti is a better choice, since it’s harmless to fish, frogs or crustaceans, and is just as safe as methoprene for humans and other animals as well.

More articles:

Footnote
[1] “Mosquito Arrives, Its Enemies Divided” by John Rather, New York Times, June 17, 2007. “Court Battles Over Spraying and Runoff Return with Mosquito Season,” by Aaron Boyd, www.Hamptons.com

Tag : Methoprene, Altosid

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