On this episode of Kentucky Health, Dr. Wayne Tuckson welcomes entomologist Dr. Jonathan Larson, PhD., from the University of Kentucky’s Extension Department of Entomology to talk about how insects affect the environment and the health of humans.
The Threats Insects Pose, and Effective Prevention Methods
Entomology is “the study of insects,” Larson says. “There’s a million known species of insects right now, and there’s a projection that there could be 30 million more left to discover.” But that doesn’t include arachnids (spiders) or worms. As Larson explains, entomologists conduct their research primarily on the six-legged organisms that make up the insect class.
Why do humans fear insects? Larson says evolutionary psychologists argue it’s in our DNA. “If you’ve ever had that weird sensation where it feels like something is crawling on you, we call that formication,” he says. “We are born to feel that sensation and to be tuned into it and to assume it’s something like a louse, or a flea, or a biting pest, because we don’t want those diseases that they carry.”
How Insects react to humans is nowhere near as emotionally complex, of course, but Larson explains some species will exhibit “pheromone-induced anger” at human intruders. For example, a bee sting chemically tags the human, which alerts other bees of the potential threat to their hive.
“They tag you so they can trail you,” he explains. “If you’ve ever seen those cartoons where the bees follow a character, that’s really true, they can do that.”
One of the most harmful insects to humans is the mosquito, and our caution about their threat is steeped in centuries of experience. “Mosquitos are probably the greatest enemy that humankind has ever known,” Larson says. “They’re the ones that have transmitted so many different viruses and problems to us.” West Nile virus, the historically devastating yellow fever, and malaria are but three of many viral diseases carried by mosquitos, he notes.
Larson says that mosquitos actually prefer certain blood types for sustenance. These “phlebotomists on the wing,” as he calls them, seek out Type O in humans.
“They are also able to detect several things about our body,” he continues. “First is usually the carbon dioxide that you’re breathing out, they’ll orient toward you… They’re downwind of you and they can detect that. If they do fly toward you, they will see your shape moving across the environment, it’s a shadow moving, they don’t have great eyesight. They’ll smell the lactic acid coming out of you, and they’ll land on you, they can sense your heat – and then they’ll find your blood vessels, poke that needle in and start feeding.”
The best ways to reduce exposure to mosquitos are to apply spray repellant, wear long-sleeved clothing, and eliminate any standing water on the property, Larson says. Mosquitos exhibit a “semi-aquatic life cycle,” he explains, starting when the females lay eggs in puddles or splash blocks collecting gutter runoff. The larvae grow in water before pupating and flying off to feed. He suggests homeowners frequently empty outdoors containers that collect water (at least once a week, he says), and dispose of tires or other unwanted items that may collect water.
“If you have standing bodies of water that you can’t get rid of, those can be treated with something called a mosquito dunk,” Larson says. This product is made up of a bacteria that will target mosquito larvae specifically, and once dissolved in water will kill them.
Fleas and mites present less serious threats but are nuisances for everyone, according to Larson. He advises pet owners to be vigilant about treating pets if they are affected and to regularly vacuum their home.
Bedbugs – small wingless insects that collect in mattresses or box springs and feed on human blood – are having a resurgence, Larson says. They can cause itchy, painful bites.
“There’s a social stigma attached to bedbugs and so sometimes people don’t seek help,” he notes. “But we do have options to deal with them. Heat treatments can help, getting a professional to come in and do some chemical control.”
Encountering Troublesome Arachnids: Ticks and Spiders
Another common scourge, the tick, is actually an arachnid, Larson says. They rely on blood meals to mature and will feed on several different hosts in the cycle. “They have to feed on all of these different animals throughout their life, which means they can possibly pick up pathogens from their first host or second host and then move it on down the line,” he explains.
Diseases carried by ticks include Rocky Mountain spotted fever and Lyme disease. Larson says the Rocky Mountain spotted fever is very common in Kentucky; since 2012, the state’s Department of Public Health has reported a 250 percent increase in the bacterial disease.
People who spend a lot of time outdoors, especially walking in woods and thickets, need to do routine tick checks, Larson says. “Any time you come in from an outdoor activity – it seems a bit extreme, but even if you’ve just been in your garden or your landscape, it’s possible that there’s a tick there,” he cautions. Persons should take off their clothes and check hairy spots or hidden places such as underarms to locate possible ticks. Of course, he recommends removing any that are found immediately to prevent or stop their feeding.
“The process of removal should involve a nice pair of tweezers that are pointy at the tip,” Larson says. “Get as close to your skin as possible, grip the tick’s head, and pull steadily up. You don’t want to grip it and rip it, and you don’t want to wiggle it out, because you can break pieces of it apart in you.”
Several spiders are also dangerous, according to Larson, starting with the brown recluse. This small spider can be identified by its khaki color and a violin shape on its cephalothorax (head and neck), but its signal feature is having six eyes instead of the eight common to most spiders. The venom from a brown recluse will cause a small hole to appear on the bite recipient’s skin, Larson says.
“If you get this small hole, usually what happens is (skin) will start to turn blue around it, and then it will get better after that, it will start to heal over the course of two to three weeks,” Larson explains. The main threat comes from a secondary infection that may develop, however, which can worsen and destroy tissue.
“Most people that say they’ve been bitten by a recluse probably haven’t. It’s actually not that common for them to bite; even when we get into their habitat, they usually run away,” Larson says.
Brown recluses are more common indoors, but the infamous black widow spider prefers outdoor areas such as gardens. While black widow venom is rarely fatal, Larson says people he’s met who have been bitten by the spider describe the illness as “the worst flu you’ll ever have.”
“You kind of get a fever, you get the chills, one person described hallucinations,” he explains. “You end up in the hospital, but you work your way through it.”
How Insects Help Humans, and Our Threat to Them
Many bugs are, in fact, beneficial to humans, either in direct, tangible ways – such as honeybees and silk moths, for example – or by helping to ensure environmental balance, Larson says. “We’re talking about regular old decomposition,” he notes. “If you don’t want to live around dog poop and dead leaves every fall, things like millipedes and other arthropod relatives of insects break down that material and return those nutrients to the earth. … And then you’ve got natural enemies – things that eat the bad bugs and help keep them in check.”
Unfortunately, efforts to eradicate damaging insects can have unintended consequences. Larson describes a phenomenon called “pest resurgence,” which occurs when humans spray an at-risk plant to kill insects that feed on it. But he says the treatment can also kill beneficial insects, which then allows the problem to resurface in the future.
“We do interrupt that process frequently, and then you enter the ‘pesticide treadmill,’ some people call it, where you’re continually having to apply these products to keep the bad bugs away,” he says.
Beyond pesticide use, other human activities are having negative consequences for insect habitats, according to Larson. In addition to the loss of Amazon rainforests or other well-known areas, he says species of insects are endangered in Kentucky any time a park or other green space is affected by redevelopment or pollution.
“There are bad bugs out there, they end up harming us due to the way that they feed, and we can prevent those interactions,” Larson concludes. “But the other big takeaway that I want to share is that insects provide a lot more good than harm. If you like flowers, if you like fruits and vegetables, you want to keep these (insects) around. So we’ve got to be very conscientious of how we take care of our environment.”