In The Language of Butterflies (Simon & Schuster, May;), Williams explores and celebrates the world of butterflies.

You write that once you saw Yale University’s butterfly collection, you were hooked. But what drew you to butterflies in the first place?

Curiosity. And greed: pure, naked, unadulterated lust to see all the beauty the natural world has to offer. I’ve been fortunate in my life to be able to enjoy plenty of the big vista stuff, the standing-on-the-mountaintop experiences like riding on the plains of Africa, visiting eagles in Yellowstone and condors in California. This time, I turned 180 degrees to look at the tiny jewels nature makes available to us right beneath our feet.

Despite recognizing the range of environmental problems facing humanity, you are optimistic about the future. Why?

It’s just who I am. But also, nearing 70, I can take the long view. Growing up in the ’50s in southwestern Pennsylvania, I thought the world was nothing but soot and belching steel mill stacks and lands destroyed by the oil industry. Everything was dead. I left, then returned after many decades. I thought I had made a wrong turn and ended up back in Vermont. Everything was green! Thank you, ’60s environmental activism! Of course, we’ve only just begun. Butterflies can help show us the way.

How do you negotiate the tension between presenting both science and human interest stories in the same book?

I guess I just don’t see any tension. To me, science is tremendous fun. Scientists are some of my favorite people. Of course, I am not a scientist, so I don’t have to publish scientific papers. But even those can be fun. Look at the gracious and graceful writing of E.O. Wilson. His sentences take my breath away.

Have the years you spent on this project and the knowledge you’ve gained changed you?

Every book I do changes me. That’s why I write. This book has taught me the elegance of the infinitesimal. What a joy to be an author.

Given all you’ve learned, do you have a favorite species?

Well, of course, I love monarch butterflies. And blue morphos and their cool Christmas tree–shaped scales. Who knew? And the delicate Karner Blues, brought back from the brink to once again rise in clouds in revitalized fields just outside of Albany. And... I guess I don’t have favorites. After all, evolution shows us that, at heart, we are all the same—with a little room for our own unique individuality.