On a horribly hot July day in 2010, I followed along as a small band of citizen scientists explored several public gardens near Washington, DC. Their quarry? Butterflies. These volunteers — and thousands more like them across the United States — were taking part in the North American Butterfly Association’s National July Butterfly Census. Their observations contribute to a body of knowledge that may help scientists better understand the rise and fall in pollinator populations across the continent.

I wrote about our butterfly expedition for the online edition of Smithsonian Magazine. Here’s a brief excerpt:

Counting butterflies is one of those things that sounds easy but isn’t. Six of us are squinting and sweating in the morning sun, cameras and binoculars in hand, in the Peterson Butterfly Garden in Northern Virginia, and the butterflies are thick. Our goal today is to conduct a census of the butterflies in this garden and several neighboring fields.

In order to count a butterfly, we first have to identify it. Jocelyn Sladen, our group leader, points to the first butterfly of the day. “That is exactly the problem,” she says. “That little black butterfly could be one of any number of species.” . . .