The surprising effect of road salt on butterflies

Salting roads in winter can tweak the physiques of butterflies the next summer.

Milkweeds and oaks, plants that caterpillars graze on, collected from alongside a country road carried higher sodium concentrations than the same species growing at least 100 meters from the splash and drift of deicing salt, says Emilie Snell-Rood of the University of Minnesota in St. Paul.

Monarch (Danaus plexippus) caterpillars raised on the sodium-boosted plants turned into males with extra thoracic muscles and females with bigger eyes and probably bigger brains than butterflies reared on the more distant foliage, Snell-Rood and her colleagues found.

A different butterfly, the cabbage white, echoed these his-and-hers effects when reared on a sodium-boosted lab diet, researchers report June 9 in the Proceedings of the National Academy of Sciences.

So is road salt good for butterflies? “I do not want that to be the take-home message,” Snell-Rood says. Instead, she says, the study demonstrates for the first time that road salt can alter how animals develop physically.

Text from Science News, with a tip of the hat to reader Bradley Ruben for bringing it to my attention.  Photo from our yard.

Related: The double-edged sword of salting roads in winter, and Cheese brine for icy roads.