The Greenest Car? A Dirty One

By JAMES GORMAN

As any car owner knows, automobiles sometimes attract aquatic insects, like mayflies. The insects mistake the shiny car surface for water and try to lay their eggs on it. In The Proceedings of The Royal Society B, published online, Gyorgy Kriska and three other Hungarian scientists ask which colors the bugs like, and "considering water insect protection in wetland habitats, we discuss the question: what is the environmentally friendly color of cars?"

Using shiny plastic sheets in different colors, the researchers tested previous observations that insects are attracted to red and to dark colors. The insects much preferred the red and the black, and the reason, the authors say, is that the light reflected from the dark surfaces is highly polarized and reflected in a horizontal direction — just like water. Light from the yellow and the white cars was less polarized and less horizontally reflected.

The authors recommend light-colored cars for visitors to wetland habitats. But even better, they say, are dirty cars, which don't fool the insects at all. "Thus," the authors conclude, "the most environmentally friendly car would be one that never gets washed." It would save on water, too.