After a caterpillar goes into its chrysalis, you would expect a beautiful butterfly to emerge. But when this parasitoid attacks, the results are very different.

Monarchs eat milkweed — and that makes them toxic to most predators. But biologist Carl Stenoien discovered one parasitoid that is immune to milkweed’s effects. Listen to hear his story.

Wasps emerging from a monarch chrysalis.
Wasps emerging from a monarch chrysalis.
Carl Stenoien

• Listen to our episode on monarch butterflies here.