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Why Are Moths Drawn to Flames?

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Around the world, moths make kamikaze dives into light bulbs and open flames with such regularity that they have their own idiom. What is it about lights that make moths so crazy?


For a long time, scientists blamed the moon. Moths used the moon as a navigational beacon, it was argued, keeping it at a constant angle to their direction of travel in order to fly straight. Light sources used by humans, whether they’re campfires or porch lights, threw a monkey wrench into this system. The moon is far enough away that the angle between it and a traveling moth isn’t going to change much, even after the moth flies a great distance. With a closer light source, though, the angle changes considerably after only a short distance. A moth confusing a light bulb or candle flame for the moon, the hypothesis went, would notice this change and attempt to correct its path by turning toward the light. After just a few course corrections, the moth would set itself into a tightening death spiral towards the light and eventually crash into it, either going down in flames or thwacking its poor little head.

On Second Thought...

Over the years, various holes were poked in this hypothesis. For one—and this is a big one—moths might not even use the moon for navigation.

There isn’t much evidence for it, especially when it comes to the over 50 percent of moths that don't migrate and wouldn’t have much use a celestial navigation aid in their short distance travels.

There’s also the fact that moths don't always circle around lights in a closing spiral like the moon hypothesis assumes. Most of the time, they actually head straight for it. Henry Hsiao, a professor of Biomedical Engineering at the University of North Carolina, has tracked moth flights as the bugs headed toward a light source and found that, most of the time, they fly in a straight line toward the light until they get very close, then veer off and circle at a steady distance.

Hsiao’s observations led him to develop a new hypothesis. He’s unsure what causes the moth to make a beeline to a light, but thinks that the circling behavior at close ranges is caused by a visual distortion common to all sighted creatures called a “Mach band.” The band is the region surrounding a bright light that is perceived as being darker than any other part of the sky. Hsiao thinks that moths hang out in the band because they want the cover of darkness for safety, and wind up circling the light until their flight path takes them away from the it (or causes them to crash into it).

Love Hurts

Another explanation, proposed by U.S. Department of Agriculture entomologists in the 1970s, is that the infrared light spectrum emitted by candle flames contains some of the exact same wavelengths of light given off by female moths' luminescent pheromones. In other words, it’s just male moths that are attracted to flames because they wrongly assume that they’re going to get lucky. This doesn’t explain their attraction to UV light, which doesn’t emit the same light wavelengths as moth pheromones, but it does say something very profound about the lure of love.

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Bite Helper
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technology
New Gadget Claims to De-Itch Your Mosquito Bites
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Bite Helper

Summer can be an itchy time for anyone who wants to enjoy the outdoors. Mosquitos are everywhere, and some people are particularly susceptible to their bites and the itching that comes with them. A new product aims to stop the suffering. Bite Helper, reviewed by Mashable, is designed to stop your bites from itching.

Place the pen-like device over your swollen bite and it will begin to emit heat and vibrations designed to quell the itch. It’s meant to increase blood flow around the area to alleviate your pain, heating your skin up to 120°F for up to 45 seconds. It’s the size of a thin tube of sunscreen and is battery powered.

Most dermatologists advise applying cold to alleviate itching from insect bites, so the question is: Will heating up your skin really work? Bite Helper hasn’t been clinically tested, so it’s hard to say for certain how effective it would be. There has been some research to suggest that heat can help increase blood flow in general, but decrease histamine-induced blood flow in the skin (part of the body’s normal response to allergens) and reduce itching overall. In a German study of wasp, mosquito, and bee stings, concentrated heat led to a significant improvement in symptoms, though the researchers focused mostly on pain reduction rather than itching.

Bite Helper’s technique "seems like a legitimate claim" when it comes to localized itching, Tasuku Akiyama, who studies the mechanisms of itching at the University of Miami, tells Mental Floss. "The increase in the blood flow may increase the rate of elimination of itch mediator from the area." However, before that happens, the heat might also make the itch a little worse in the short-term, he cautions. This seems to be borne out by user experience: While Mashable's reviewer found that using the device didn’t hurt at all, his daughter found it too hot to bear for more than a few seconds.

If the device does in fact relieve itching, though, a few seconds of pain may be worth it.

Bite Helper is $25 on Amazon.

[h/t Mashable]

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Oakley Originals, Flickr Creative Commons // CC BY 2.0
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Animals
Could Imported Sperm Help Save America’s Bees?
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Oakley Originals, Flickr Creative Commons // CC BY 2.0

It might be time to call in some sexual backup for male American bees. Scientists have started impregnating domestic honeybees with foreign sperm in the hopes that enlarging the gene pool will give our bees a fighting chance.

These days, the bees need all the help they can get. Colonies across the globe are disappearing and dying off, partly due to the increased use of neonicotinoid pesticides and partly from a parasite called the varroa mite. The invasive mite first landed on American shores in 1987, and it's been spreading and sickening and devouring our bees ever since.

Part of the problem, researchers say, is that the American bee gene pool has gone stagnant. We stopped importing live honeybees in 1922, which means that all the bees we've got are inbred and, therefore, all alike. They lack the genetic diversity that allows species to adapt to changing conditions or new threats. So when the mites come, they all get hit.

Many apiarists now rely on anti-mite pesticides to keep their charges safe. While these treatments may help keep the mites away, they aren't great for the bees, either—and the mites have begun to develop a resistance. But beekeepers feel like their hands are tied.

"I lost 40 percent of my colonies to varroa last fall," Matthew Shakespear of Olson's Honeybees told NPR. "I'm not taking any more chances. We've already done five treatments, compared with the two treatments we applied this time last year."

But there might be another way. Experts at the University of Washington have started to—how can we put this delicately?—manually encourage drones (male bees) in Europe and Asia to give up their sperm. All it takes is a little belly rub, and the drone, er, donates 1 microliter of fluid, or one-tenth of the amount needed to inseminate a queen bee.

"They're really accommodating," bee breeder and researcher Susan Cobey told NPR. 

It's hardly a painless procedure, but researcher Brandon Hopkins told Mental Floss it's no worse than sex in the wild. "In natural mating he uses pressure from muscles and hemolymph to evert [his genitals], (inflating it and forcing it to pop out)," Hopkins wrote in an email. "In the lab we apply pressure to the head and thorax to create similar pressure to cause the eversion. In both cases (naturally and artificially) the male dies from the process of mating."

So far, the scientists' attempts to crossbreed foreign and domestic bees have been successful. Within their test colonies, genetic diversity is up.

"This doesn't mean they are superior in performance to the other bees," Hopkins told NPR. "It means we have a better chance of finding rare and unique traits." Traits, Hopkins says, like genetic resistance to the varroa mites—a quality shared by donor bees in Italy, Slovenia, Germany, Kazakhstan, and the Republic of Georgia.

Other beekeepers are opting for a more hands-off approach, introducing imported queens to their domestic hives. Shakespear bought his from Cobey, who reared them from bees she collected in Slovenia.

"Maybe these new genetics can deal with the varroa mites naturally," Shakespear said, "rather than having to rely on chemicals. It's time to start widening our gene pool."

[h/t The Salt]

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