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Why Are Moths Drawn to Flames?

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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These Fake Flowers Could Help Scientists Study At-Risk Bees
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If you haven't heard, the world's bees are having a crisis. According to one recent study, bee populations in some areas have plummeted by 75 percent in a quarter of a century. Some countries have introduced legislation banning certain pesticides in response to the news, but solving the complicated problem will likely require much more research. In order to gather better data on bee behavior, one new media artist has developed a machine that can give scientists a bug's-eye view.

As Co.Design reports, Michael Candy's Synthetic Pollenizer is designed to blend into a bee's natural environment. Yellow circles bolted around the opening of the device imitate the petals on a flower. Tubes pump real nectar and pollen into the center of the fake flower, so when bees land on it to feed, they're collecting real reproductive materials they can spread to the next plant they visit.

Candy, who's based in Brisbane, Australia, originally conceived the apparatus as a way for scientists to track the pollinating behaviors of bees. The synthetic flower is outfitted with cameras and dyes, and with enough of them distributed in the wild, researchers could see which bees travel to certain places and how long they stay.

After his concept reached the final round of the Bio Art and Design awards in the Netherlands, Candy decided to create his own prototype with help from an urban beekeeper in Melbourne, Australia. The invention worked: Bees mistook it for real flora and carried pollen from it to their next destination. But to use it for tracking and studying bees on a larger scale, Candy would need to build a lot more of them. The pollinators would also need to be scattered throughout the bees' natural habitats, and since they would each come equipped with a camera, privacy (for nearby residents, not the bees) could become a concern.

Even if the concept never gets the funding it needs to expand, Candy says it could still be used in smaller applications. Fake flowers designed to look like real orchids, for example, could encourage the pollination of endangered orchid species. But for people studying dwindling bee populations, orchids are low on the list of concerns: 30 percent of all the world's crops are pollinated by bees [PDF].

[h/t Co.Design]

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Health
A Chemical in Bed Bug Poop Might Be Making You Feel Sick
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Bed bugs can give you nasty bites and a lifetime of nightmares, but scientists have long wondered if the creepy parasites can pass diseases to their hosts. For years, the general consensus was no: Unlike ticks, mosquitos, and other insects that are known to feast on human blood, bed bugs aren't packing any harmful pathogens in their bites. Yet according to a new study, spotted by Gizmodo, the bugs don't need to nibble on us to make us sick. Histamines in their poop might be aggravating our immune systems.

For their study, recently published in the journal PLOS One, scientists at North Carolina State University tested the dust in a bed bug-infested apartment complex. They found that samples from some infested homes had histamine levels 20 times higher than those without bed bugs. This was still the case three months after the buildings had been treated by exterminators.

Histamine is a chemical compound produced by our bodies. In small amounts, it works as a vital part of our immune system. It's activated in the presence of allergens, irritants, and pathogens. Say a puff of dust goes up your nose: Histamine is what prompts your body to sneeze it out. It's also the culprit behind the watery eyes, runny nose, and itchy skin you might experience during an allergy attack (which is why you might take an antihistamine to calm these symptoms).

But we're not alone in our ability to produce histamine. Recent research has shown that the chemical is present in bed bug feces. When the insects poop, they spray histamines into the same air that homeowners breathe. A few whiffs of the stuff is likely nothing to worry about, but scientists are concerned about the effects environmental histamine can have on people over an extended period of time. The chemical compound can cause allergic reactions on its own and possibly make us more vulnerable to existing allergens. The implications are especially serious for people with asthma.

"Dermal, nasal, or respiratory responses (e.g. bronchial reactivity) to histamine in clinical tests suggest that exposure to histamine in the environment would constitute a significant health risk, although information on environmental exposure is limited," the study authors write.

For now, scientists can do nothing but speculate on what these results might mean for public health. Humans are prepared to treat only histamine that's produced by our own bodies, and dealing with the effects on histamine spread by bed bugs is uncharted territory for doctors and scientists. How exactly bed bugs obtain the chemicals in the first place is also unclear, but researchers suspect that it's a combination of the blood they suck from us and histamine they make on their own as a type of pheromone, indicating to other bed bugs that a place is safe to invade.

Following this study, the North Carolina State scientists plan to conduct more intensive research on the impact histamine produced by bed bugs is having on the people who live with it. While the best way to eradicate histamine in bed bug poop is still a mystery, there are plenty of ways to deal with the bugs themselves if you suspect you have an infestation.

[h/t Gizmodo]

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