Dr. Universe

Dear Dr. Universe, I saw a caterpillar and a butterfly in the neighbor’s yard. So my question is, what exactly happens inside the little sack they’re in while they transform into a butterfly and how exactly do they do it? – Eston

Dear Eston,

Springtime sets the stage for one of the greatest transformations in the natural world.

“It’s the construction of a butterfly or moth from caterpillar soup,” said my friend David James, an entomologist at Washington State University. James studies the science behind metamorphosis, or how a creature transforms.

Before becoming butterflies, caterpillars ente...