Chances are you’ve heard the phrase “like a moth to a flame”——and probably seen it in action at a nighttime fire or barbecue, too. It turns out, however, this age-old saying may not be quite right. Rather than being attracted to light, moths’ tendency to fly toward brightness is a behavioral response to help them determine which way is up, suggests a new study published in the journal Nature Communications.
To avoid falling down to the ground, insects need to know which way is up, says study coauthor Yash Sondhi, a National Geographic Explorer. Without systems to maintain spatial (空间的) orientation, the brightness of the sky, even at night, has always been a strong indicator of “up”——until artificial lights came along. If they mess that up, they start plummeting.
Sondhi and a team of researchers set up experiments to investigate how different lights influence flight behavior. First, the researchers suspended a light bulb from a rope between two trees——resembling a typical downward-pointing light——and in a separate test, they turned the light upward by mounting it on a tripod (三脚架). In both cases, insects leaned their winged backs to the bulb. But when the light was pointed up, the insects often bumped to the ground.
What if the light is spread over a wide area? The researchers stretched a large white sheet across the tree and projected a UV light on it. If the insects were truly “attracted” to the light, they should fly up toward it. Instead, the insects cruised (巡航) straight through this illuminated corridor, flying how they would during the day. The team then placed the sheet on the ground and shined the light on it, which is when something truly odd happened: All these moths flying over it turned upside down and crashed out of the sky. Directionality of light is a huge factor in the pattern we have seen, not just brightness or color.
“Artificial lights may cause a mismatch between the insect’s sense of which way is up and true direction of gravity, which spells trouble for insects population.” says Sondhi.
8. What can be inferred about “like a moth to a flame” in the new study?
A.A moth is generally attracted by a flame. | B.Artificial lights are valuable for a moth. |
C.Brightness indicates up for a moth. | D.A moth has a sense of direction. |
9. What does the underlined word “plummeting” in paragraph 2 mean?
A.Crashing. | B.Speeding. | C.Freezing. | D.Suspending. |
10. What lights influence insects most in the experiments?
A.UV lights on the tree. | B.Upward-pointing lights. |
C.Downward-pointing lights. | D.Lights of different colors. |
11. What is Sondhi’s attitude toward artificial lights?
A.Concerned. | B.Dismissive. | C.Doubtful. | D.Neutral. |