A Firefly's Twinkle Doubles as a Warning Sign to Predators


A group of fireflies twinkling on a summer's night may look peaceful, but those flashing lights can send an unsettling message: 'If you eat me, you'll regret it.' That's what a team of researchers discovered when conducting a study published in Science Advances.

According to the new research, reported by ScienceNews, a firefly's flashing behind acts as a warning signal to predators like big brown bats. Entomologists have long known that fireflies use their lights to attract mates, but the suspicion that they also use them to avoid becoming dinner wasn't confirmed until recently.

To investigate this theory, a team of scientists from Boise State University and other institutions exposed fireflies to three bats with no experience hunting the insects. Fireflies contain toxic chemicals that make them unappealing to predators. After tasting a few of the bugs and spitting them out, the bats learned to stop going after them altogether.

To see what part light played in these interactions, the researcher conducted a separate experiment. They attached tiny paper belts to each firefly and painted them with two coats of black paint—a process that took about 45 minutes for each specimen. The result was a cloak that effectively hid the fireflies' light show. When bats were set loose on the snuffed-out group, it took the predators about twice the amount of time to realize the fireflies were toxic and ignore them. With no visual warning signs to tip the bats off, the study authors suspect that the bats eventually learned to identify the insects from their flight patterns via echolocation.

Fireflies don't light up only when they see a bat swooping their way: Males each have their own "flash fingerprints" they use to attract mates, and females blink in response when they see a display they like. The new study suggests that predators' reaction to this bioluminescent adaptation may have influenced its evolution.

[h/t ScienceNews]

Bad News: The Best Time of the Day to Drink Coffee Isn’t as Soon as You Wake Up


If you depend on coffee to help get you through the day, you can rest assured that you’re not the world's only caffeine fiend. Far from it. According to a 2018 survey, 64 percent of Americans said they had consumed coffee the previous day—the highest percentage seen since 2012.

While we’re collectively grinding more beans, brewing more pots, and patronizing our local coffee shops with increased frequency, we might not be maximizing the health and energy-boosting benefits of our daily cup of joe. According to Inc., an analysis of 127 scientific studies highlighted the many benefits of drinking coffee, from a longer average life span to a reduced risk for cancer, heart disease, type 2 diabetes, and Parkinson’s disease.

Sounds great, right? The only problem is that the benefits of coffee might be diminished depending on the time of day that you drink it. Essentially, science tells us that it’s best to drink coffee when your body’s cortisol levels are low. That’s because both caffeine and cortisol cause a stress response in your body, and too much stress is bad for your health for obvious reasons. In addition, it might end up making you more tired in the long run.

Cortisol, a stress hormone, is released in accordance with your circadian rhythms. This varies from person to person, but in general, someone who wakes up at 6:30 a.m. would see their cortisol levels peak in different windows, including 8 to 9 a.m., noon to 1 p.m., and 5:30 to 6:30 p.m. Someone who rises at 10 a.m. would experience cortisol spikes roughly three hours later, and ultra-early risers can expect to push this schedule three hours forward.

However, these cortisol levels start to rise as soon as you start moving in the morning, so it isn’t an ideal time to drink coffee. Neither is the afternoon, because doing so could make it more difficult to fall asleep at night. This means that people who wake up at 6:30 a.m. should drink coffee after that first cortisol window closes—roughly between 9:30 a.m. and 11:30 a.m.—if they want to benefit for a little caffeine jolt.

To put it simply: "I would say that mid-morning or early afternoon is probably the best time," certified dietitian-nutritionist Lisa Lisiewski told CNBC. "That's when your cortisol levels are at their lowest and you actually benefit from the stimulant itself."

[h/t Inc.]

26 Amazing Facts About the Human Body

Mental Floss via YouTube
Mental Floss via YouTube

At some point in your life, you've probably wondered: What is belly button lint, anyway? The answer, according to Mental Floss editor-in-chief Erin McCarthy, is that it's "fibers that rub off of clothing over time." And hairy people are more prone to getting it for a very specific (and kind of gross-sounding) reason. A group of scientists who formed the Belly Button Biodiversity Project in 2011 have also discovered that there's a whole lot of bacteria going on in there.

In this week's all-new edition of The List Show, Erin is sharing 26 amazing facts about the human body, from your philtrum (the dent under your nose) to your feet. You can watch the full episode below.

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