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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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Which Rooms In Your Home Have the Most Types of Bugs, According to Entomologists 
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Insects can make any home their own, so long as it contains cracks, doors, and windows for them to fly, wriggle, or hitchhike their way in. And it turns out that the creepy crawlers prefer your living room over your kitchen, according to a new study that was recently highlighted by The Verge.

Published in the journal Scientific Reports, the study looked at 50 homes in Raleigh, North Carolina, to measure their insect populations. Entomologists from both North Carolina State University and the California Academy of Sciences ultimately discovered more than 10,000 bugs, both alive and dead, and a diverse array of species to boot.

The most commonly observed bugs were harmless, and included ladybugs, silverfish, fruit flies, and book lice. (Luckily for homeowners, pests like bedbugs, termites, and fleas were scarcer.) Not all rooms, though, contained the same distribution of many-legged residents.

Ground-floor living rooms with carpets and windows tended to have the most diverse bug populations, as the critters had easy access inside, lots of space to live in, and a fibrous floor habitat that could be either a cozy homestead or a death trap for bugs, depending on whether they got stuck in it. The higher the floor level, the less diverse the bug population was, a fact that could be attributed to the lack of doors and outside openings.

Types of bugs that were thought to be specific to some types of rooms were actually common across the board. Ants and cockroaches didn’t limit themselves to the kitchen, while cellar spiders were present in all types of rooms. As for moths and drain flies, they were found in both common rooms and bathrooms.

Researchers also found that “resident behavior such as house tidiness, pesticide usage, and pet ownership showed no significant influence on arthropod community composition.”

The study isn’t representative of all households, since entomologists studied only 50 homes within the same geographical area. But one main takeaway could be that cohabiting bugs “are an inevitable part of life on Earth and more reflective of the conditions outside homes than the decisions made inside,” the researchers concluded. In short, it might finally be time to make peace with your itty-bitty housemates.

[h/t The Verge]

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UK Agrees to Ban Pesticides That Destroy Bee Populations
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As bee populations around the globe continue to dwindle, more countries are stepping up to save them. The latest nation taking action against the threat of pollinator decline is Britain. The UK’s environment secretary Michael Gove recently announced that the country will join the European Union in restricting a type of pesticide harming bees.

The decision was made in light of a German study reporting that the number of flying insects in some areas have declined by 75 percent in just a quarter of a decade. Of the species dying off en masse, bees are the most concerning: The insects pollinate a significant portion of our crops, and without them humans could face an agricultural crisis. “These particular flying insects are absolutely critical to the health of the natural world,” Gove wrote for The Guardian. “Without a healthy pollinator population we put the whole ecological balance of our world in danger.”

The alarming state of bee populations is likely a mix of several factors, but human-made insecticides are one of the biggest contributors. Neonicotinoids, the chemical compounds covered by the proposed ban, are the most commonly used insecticides on Earth, and they’ve also been shown to have devastating effects on bee colonies. Getting rid of them completely was first proposed by the European Union in 2013, and after initially opposing the move, the UK is finally getting on board.

Neonicotinoids are slowly being phased out in the U.S., where beekeepers have been reporting bees disappearing from their hives for the last decade or so. If you want to make your backyard a more hospitable place for your tiny, flower-loving neighbors, here are some ways you can help right now.

[h/t The Guardian]

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