The Loh Down On Science

Bug Spray

Scientists finally figure out why bugs hate insect spray. It smells bad!

What is DEET? I mean, really?

This is Sandra Tsing Loh with the Loh Down on Science

Saying sure, okay, DEET is short for N,N-Diethyl -meta-toluamide, the insect repellent agent first used in World War II.

But how does it work?

Well-- Mosquitoes find us by sensing our body heat and odor of lactic acid. That's the chemical produced during normal metabolism and exercise.

Mosquitos smell odors through antennae neurons. Some neurons sense pleasant odors, others, unpleasant ones.

Experts traditionally figured that DEET somehow jams mosquitos' sense of smell, so they can't sniff us out.

But not so, now says entomologist Walter Leal at the University of California, Davis. He tested DEET's effects by setting up feeding stations. Some were laced with pleasant smells, others odor free, and some sprayed with DEET.

The skeeters ZOOMED to stations with pleasant -- or no--smells. But they steered clear of DEET.

Leal's surprising conclusion, which could lead to new ways to design insect sprays? The mosquitos' ability to smell was intact. They just hate the smell of DEET.

I know maybe you were expecting something more amazing, but no. Yucky smell. Oh!


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