We were on a gravel road that wound through a hayfield—just walking through, talking as we went. At first the butterflies were so tiny that we didn’t really notice them. But then they were everywhere, kicking up like little orange sparks. Hundreds rose and surrounded us, soft wings against our bare arms, then settled back on the road as we passed. A few dozen labored out into the surrounding meadow and disappeared into the oatgrass and hawkweed and brome.
They were European skippers, Thymelicus lineola, one of the most common butterfly species in New England. They’re so common, according to the North American Butterfly Association (NABA) website, that in places and at times, they outnumber all other butterfly species combined. Look for mobs of them this summer in fields and on dirt roads.
The butterfly congregations you see along dirt roads relate to a habit that entomologists call “puddling.” The water in road puddles has absorbed salts and minerals from the soil underneath it, which the butterflies use to supplement their diet. (Minerals are also obtained from urine and dung, which explains the butterfly congregations on piles of scat.) If there are no puddles on a road, butterflies may land anyway, regurgitate into the earth, and then drink in the hope of leaching nourishment from the soil.
Thanks to Kent McFarland and entomologist Trish Hansen for their insight.