在线英语听力室_免费在线英语听力学习网站

This is Scientific American's 60-second Science, I'm Bob Hirshon.

If you're a skunk¹, or fox, or very strange person, and you poke² your nose under a rock in the desert Southwest, looking for something to eat, you might be surprised to see dozens of bright blue and red beetles⁴ scurrying⁵ t?????o and fro. And you might be really curious as they quickly turn their butts⁶ toward you. 

But the curiosity wouldn't last long: a couple thousandths of a second later, a fusillade of boiling hot, toxic⁷ spray would drive off both you and your musings.

The insects with the spraying butts are fittingly named bombardier beetles. And they can fire off 500 pulses per second of caustic⁸ defensive⁹ chemicals. What also makes them unusual is that even though the nocturnal beetles are solitary¹⁰ by night, dozens or even hundreds of them—of various bombardier species—snuggle together under rocks during the day.

"It's actually a fairly unusual phenomenon for different species to regularly associate with one another."

University of Arizona entomologist Wendy Moore.

"But these guys are sheltering together, and they're actually doing it intentionally¹¹, you know, because they have more options. There's plenty of options within the habitat that they could actually segregate¹² out by species, and they don't."

In fact, when Moore and her colleagues put beetles into a setting where they had cozy¹³ solitary hiding places, as well as hiding places already packed with other beetles, the newcomers invariably chose to shelter with others under the crowded rocks. The study is in the journal PLOS One.

Moore says buddying¹⁴ up may help protect the insects from predators¹⁶.

"Bombardier beetles produce benzoquinones, which are really powerful as a matter of defense¹⁷, but these other beetles produce other kinds of defensive chemicals that probably contribute to a big chemical cocktail¹⁸ for a vertebrate predator¹⁵ that might find them during the day."

In addition, a lone¹⁹ beetle³, no matter how brightly colored, might not scare off a predator as effectively as a whole bunch of beetles.

"If you imagine being a predator, even a human, turning over a rock and seeing hundreds of these blue and red beetles going in every direction, that serves as a bigger advertisement to them of their toxicity²⁰. It may help them be able to avoid attack."

So whatever you can say about an encounter with these fearsome little insects, you can't say that you weren't warned.

Thanks for listening for Scientific American — 60-Second Science. I'm Bob Hirshon.