Parasitoids kill butterflies and moths by eating them from the inside out.

Some lay their eggs on or in an egg, caterpillar, or chrysalis.  Others lay eggs on plants. When the parasitoid larvae hatch, they grab onto and enter into a caterpillar that wanders over them.

Braconid Wasp
Chalcid Wasp
Chalcid Wasp in Black Swallowtail Chrysalises
Chalcid Wasps in Monarch Chrysalises
Euplectris in Caterpillars
Tachinid Fly