Pass the Salt, Please; March 1996; Scientific American Magazine; by Wu; 1 Page(s)

Sodium, essential for nearly every metabolic reaction in the body, is sometimes a rare commodity, so it¿s no wonder that many animals seek out salt licks, sweat, termite mounds and Big Macs. Some moths, though, are able to meet their salt needs with an ability that would put any barfly to shame. They guzzle almost 40 milliliters of water in a few hours--the human equivalent of more than 40,000 liters, at four liters per second--to absorb the sodium they need.

Naturalists, after long observing butterflies and moths drinking water from puddles, came to suspect that the quest for salt drove the behavior. In the 1970s researchers found that when given a choice of progressively saltier solutions, butterflies usually drank from the saltiest mixture available. Now chemical ecologists Scott R. Smedley and Thomas Eisner of Cornell University have confirmed the role that "puddling" plays in sodium procurement, after studying nature¿s champion puddlers, male Gluphisia septentrionis moths.