The next time a mosquito attacks you, blame yourself. You're a delicious treat because of your genetic makeup. According to a study released in April 2015 and published in PLOS One, a person's DNA is one of the determining factors for why the bugs bite humans - or don't bite, as the case may be. Researchers at the London School of Hygiene and Tropical Medicine asked 37 sets of twins to put their hands in a tube containing 20 blood-hungry female mosquitoes. Blood contains protein, which the mosquitoes need to reproduce. The bugs took a whiff of each hand. They flew toward some hands, while staying away from others [sources: Stein].
Specifically, the mosquitoes had the same level of attractiveness toward identical twins, who share most of their DNA, and different levels of attractiveness toward fraternal twins, who don't share as much. This told scientists that genes were the determining factors in why they bite or don't bite, possibly creating a natural repellent in some people. The next step researchers say is to identify those genes and then perhaps use them as a basis for a new bug repellent [sources: Stein, Kaplan].
The experiment was just one of many, many scientific inquiries into mosquitoes. Whether researchers are investigating their taxonomy, biology, response to biopesticides or something else, mosquitoes are one of the planet's most studied insects, but they're not the only ones. Here are 10 that lead the list.
10. Monarch Butterflies
For more than a century, monarch butterflies (Danaus plexippus) have come under intense scientific scrutiny, mostly because of their migration habits and dwindling population. Monarchs east of the Rockies migrate to Mexico each fall from the United States and Canada. Tens of thousands often land on a single tree on their trek south. But as each year passes, their population declines, mainly because of habitat destruction. Only 20 years ago, a billion monarchs made the trip to Mexico from the U.S. or Canada. Their numbers have now plummeted by more than 90 percent. As a result, scientists have studied the behaviour of the orange and black flutterers, their biology and their environs, trying to find ways to bolster their population [source: Gross].
Scientists have been especially concerned by the destruction of milkweed fields on which the monarchs feast. Researchers say that over the past 15 years, the number of milkweed plants in the Midwest has dropped by 58 percent, which correlates with an 81 percent drop of monarch butterflies. Studies also show that the use of glyphosate herbicide is destroying monarch eggs that the butterflies deposit on each milkweed plant. In addition, the increased planting of genetically modified glyphosate-tolerant corn and soybeans is muscling out fields of milkweed [sources: Pleasants and Oberhauser, Gross].
9. Head Lice
Head lice (Pediculis humanus capitis) have been a head-scratching nuisance for millennia. The wingless, six-legged, blood-sucking insects make their homes on the scalps of humans because food is plentiful and the environment warm and moist. In the United States, between 6 million and 12 million children ages 3 to 11 get lice each year [source: CDC].
Many scientists look at how resistant the bug has become to various treatments. John Clark, a professor of environmental toxicology and chemistry at the University of Massachusetts at Amherst, found that some lice have mutated into "super lice." Clark says one specific mutation allows head lice to resist two insecticides, pyrethrins and pyrethroids, which are found in many over-the-counter treatments. Clark estimates that 90 percent of head lice in the United States have the mutations [source: Clark].
8. Honeybees
Entomologists around the world spend a lot of time studying honeybees (Apis mellifera), thanks to their critical role in farming. Not only are the buzzing bugs important to the production of honey, but they also are the chief pollinators of crops. In the U.S., all pollinating insects contribute around US$24 billion to the economy. Of that number, honeybees contribute US$15 billion by pollinating more than 130 fruit and vegetable crops [source: The White House]. The bees pollinate 80 percent of all flowering crops, which is nearly 33 percent of everything humans eat [source: Boland]. Losing them can negatively affect all of us. If they die out, honeybees will take most pollinated plants with them.
Much of the research focuses on Colony Collapse Disorder (CCD). CCD takes place when all (or nearly all) of the adult bees in the colony, except the queen, die out. No one knows exactly why CCD occurs, but scientists are looking to various pathogens, parasites and environmental stressors for answers.
Aside from the crop question, studying the biology, evolution and physiology of honeybees may yield benefits for human health. Some doctors have used bee venom to treat autoimmune diseases and arthritis [source: Agriculture Defense Coalition]. For example, the medical director of the Monmouth Pain Institute in Red Bank, New Jersey, spent two years in the 1980s treating 108 arthritis patients with bee venom. Dr. Christopher Kim found that most of the patients improved after receiving 12 injections, but such treatments still warrant additional study [source: Downey].
7. Fire Ants
The infamous red imported fire ants (Solenopsis invicta) first arrived in the United States in the 1930s, probably aboard a Brazilian cargo ship [source: National Geographic]. Since then, they've proved to be an ecological nightmare for many communities, especially in the South. They can attack an animal and strip its carcass within hours. In addition, fire ants are marauders, attacking and stinging as a group. Their venom is toxic and burning. The ants have marched across many states, devastating ecosystems by stripping the soil of vegetation and by eradicating certain species from the area. In Texas alone, red fire ants are responsible for an estimated US$1.2 billion in damage each year [source: TAMU].
Researchers focus on eliminating and controlling the pest through genetic, chemical and non-chemical means. One study even looked at whether home remedies, such as spreading coffee grounds, cinnamon, club soda or cayenne pepper on the ground could repel the ants. The conclusion? Largely useless unless, as one entomologist noted, you actually drowned the ants with club soda [source: Williams].
6. Tree-killing Insects
Tree-killing insects deserve a category all their own. Mountain pine beetles (Dendroctonus ponderosae), emerald ash borers (Agrilus planipennis), gypsy moths (Lymantria dispar) and more are devastating the world's forests, which is why scientists spend serious time studying their behaviour and their biology. In 2012, the emerald ash borer, a beetle not quite the size of a penny, took Connecticut by surprise, drilling holes and laying eggs in the state's ash trees. The beetles killed thousands of trees as they ate through them during each stage of larval development [source: DEEP].
Over the years, the gypsy moth has defoliated millions of arches of hardwoods in the East. In California, the tiny polyphagous shot hole borer (one of the ambrosia beetles) has resisted all eradication efforts. They don't eat the wood of the tree. Instead, they drill tunnels and then deposit fungal spores, which they later harvest to feed their larvae. The fungus spreads, killing the tree. It's tough to kill the shot hole borer with pesticides because the tree shields the insect from the deadly chemical. Scientists even studied whether sex pheromones could lure them out [source: Khan].
Most studies of these and other tree-killing pests centre on eradication. Researchers at Northern Arizona University, for example, looked at how sounds could stop armies of bark beetles that have devastated pines in the West. Although Queen, Guns N' Roses and the voice of Rush Limbaugh played backward did little to stop the beetles, recordings of the beetle's own sounds did the trick. Once they heard their own noise, the beetles stopped mating, burrowing and feeding. A few fled. Some killed each other [source: McKinnon].
5. Maggots
For centuries, people used maggots for medicinal purposes. The bugs helped to clean injuries and prevent infection. The unsightly critters were good at what they did because they fed only on dead tissue. When antibiotics came along, maggots were relegated to the dustbin of history. Now, however, maggot use in modern medicine is on the rise. In fact, the U.S. Federal Drug Administration approved their use as a "medical device" back in 2004. One study published in 2013 concluded that maggots do a better job of clearing out dead tissue after surgery than a doctor could with a scalpel and scissors. Another studied showed that maggot secretions battle some pathogens, which can help stop infections [source: Arnold].
Moreover, forensic entomologists have a soft spot for maggots and adult flies. Since flies are the first bugs to arrive when a body starts to decompose, figuring out which species settles on a body and lays its eggs is important. Different types of flies appear at different times and grow at different rates. Among the first to show up on a body are blowflies and flesh flies. The longer a body decomposes, the more flies appear [source: Lee].
4. Cockroaches
You would think that after having been around for 350 million years or so, there would be nothing left to learn about the cockroach (Blattodea order). Not so. Scientists study them all the time. They study their taxonomy, biology and ecology. They observe how they act and what they eat. Researchers look at their genitalia, anal plates and abdomens.
One study conducted in 2007 by researchers at Vanderbilt University focused on how the bugs learned. Researchers taught individual cockroaches to prefer peppermint, which the bugs normally hate, over vanilla, which they normally like. Scientists trained the insects during a 24-hour cycle. They learned that those trained at night had better memories than those trained in the morning. Scientists determined that the cockroach's memory is closely linked to its circadian cycle, more commonly known as a biological clock [source: Vanderbilt University]. Another study discovered that when isolated, cockroaches became shut-ins. They liked to stay at home. They also ate less and couldn't tell when a female wanted to mate [source: Lihoreau et al.].
3. Ladybugs
When was the last time you shooed a ladybug (Coccinellidae family), or stomped on its behind? Chances are, never. Most people love ladybugs. With 5,000 species, there are a lot to love. Their colourful domes make them the most recognizable insects in the wild. North Dakota even declared the ladybug the state insect. Yet, no one loves the bug more than farmers do. Ladybugs are hearty eaters, chowing down on aphids (plant lice), mites and other crop-destroying pests. Not all ladybugs are beneficial, however. Many species eat plant themselves. The Mexican bean beetle destroys beans. The squash beetle, eats, you guessed it, squash [source: National Geographic].
Scientists study ladybugs for a variety of reasons, such as trying to figure out why some common species are becoming rare. Other scientists are experimenting with how ladybugs can take the place of pesticides. In Japan, researchers bred ladybugs that don't fly so farmers can use them as a non-chemical biopesticide. It took scientists 30 generations to breed the bugs, which stay on the plant and devour other bugs. The non-flying, bug-eating ladybug has reduced damage to Japan's mustard spinach crop by 90 percent [sources: Hellmann].
2. European Corn Borer
The moth-like European corn borer (Ostrinia nubilalis) is one of the most heavily studied insects you never heard of. First identified in Boston in 1917, the European corn borer came to the United States as it hitched a ride on corn from Hungary and Italy. Since then, it established itself as a pest in the eastern United States and Canada. Coloured yellow and tan, the European corn borer has a wingspan of about an inch. Its larvae like to feed on the leaves of different crops, especially corn.
The cost of controlling the corn borer and the damage it causes is roughly US$1 billion a year. Scientists mostly want to know how to stop or manage the bug's spread. They look at the bug's mating habits and diet, as well as how it spreads. Some of their research focuses on using genetically modified corn that produces an insecticidal protein from the bacterium Bacillus thuringiensis. That protein protects the plants from the insect [sources: Penn State, Bessin].
1. Fruit Fly
Perhaps no bug, not even the mosquito, is as widely studied as the fruit fly (Drosophila melanogaster). Scientists have poked at the fruit fly for more than 100 years. They've been able to learn about genetics and how to treat certain diseases including amyotrophic lateral sclerosis (ALS), Parkinson's, Alzheimer's and Huntington's disease.
Fruit flies are well understood and used as a stand-in for humans. That's because we share 75 percent of our genes with the flies. Hundreds of labs in the United States are devoted to fruit fly research. Scientists are not only interested in the bug's genetic makeup, but also in its biology. Plus, they're easy to work with, and scientists can keep millions of them without taking up much space. They can't do that with a rat or a mouse [sources: Jolly, University of North Carolina].
Author's Note: As I write this, the corpses of Asian ladybugs litter my office carpet. They have little to eat here and die within a few days. Why the infestation? Science has provided an answer. My house is yellow, and as such, it serves as a beacon for the bugs. Studies show Asian ladybugs like bright surfaces and the sunny part of a building, which is why every spring I have to vacuum them up when they come knocking. I'm glad they're not cockroaches.
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Article Sources:
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Top image: An Anopheles stephensi mosquito is obtaining a blood meal from a human host through its pointed proboscis. Credit: Jim Gathany/Wikimedia Commons.
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