The monarch butterfly’s migration is a thing of beauty and mystery. So mysterious that the location of where they overwintered in Mexico wasn’t even known to American and Canadian scientists till 1975. They simply would disappear in the fall and then return the next spring. They’ve been disappearing again, but this time for less mysterious reasons: mostly habitat loss and the use of pesticides. In 2017 the Federal Highway Administration decided to see what they could do to help.