Vampirism isn’t just for bats and Edward Cullen anymore. Some ordinary insects are also beginning to covet human blood, sweat, and tears, because these fluids contain valuable salt that is hard to find in their natural environment. Surprisingly, many species are even preferring salt to energy-rich sugar.
The idea that salt attracted bugs first dawned on a team of sweaty scientists studying insects in Peruvian forests. Puzzled by the swarms of tiny bees attacking them, the scientists soon realized that the bees were trying to get a taste of their sweat. Animals need salt to activate nerves and muscles, and to maintain water balance in their cells.
Intrigued, the scientists littered the forest floor with hundreds of vials filled with either sugar or salt and counted the ant species they baited. They found that ant species living within 100 kilometers of the oceans (with easy access to salt) chose sugar over salt. But ant species living farther inland had a noticeable preference for salt. Reporting in the Proceedings of the National Academy of Sciences, the scientists say the salt cravings were only seen in vegetarian ants, since carnivorous ants can get enough salt from the bodies of their prey.
Which brings us to the vampire moths.
In an unrelated study, entomologists say a population of fruit-feeding moths (Calyptra thalictri) have evolved the habit of feeding on blood. The moths, found in Russia, can use their long tongues, lined with sharp hooks and barbs originally adapted to pierce fruit, to get under human skin. The scientists say they have observed these moths sucking blood from their own hands for more than 20 minutes at a time. [Ed. note: That is just nasty.] Since only the male moths engage in blood-feeding, the scientists suspect they are offering the salt from the blood as a gift to females during copulation.
Now isn’t that romantic?