Cocoon of salt marsh caterpillar, Estigmene acrea, opened to reveal oblong, dark red puparia of a parasitic (parasitoid) tachinid fly and shriveled skin of mature larva (caterpillar) it killed.

Cocoon of salt marsh caterpillar opened to reveal oblong, dark red puparia of a parasitic (parasitoid) tachinid fly and shriveled skin of mature larva (caterpillar) it killed.; El Toro, California Credit: Earl R. Oatman
Credit: Earl R. Oatman