The mystery of where some animals disappear to each year puzzled early naturalists. Do swallows hibernate in mud or under water? Where do our butterflies suddenly appear from each spring? The discovery of the swallow's epic migration and the butterfly's magical transformation were scientific stories cloaked in mystery and controversy.

Encoded with permission for digital streaming by Infobase on December 24, 2014. Learn360 is distributed by Infobase for Films for the Humanities & Sciences, Cambridge Educational, Meridian Education, and Shopware.

Barnacle Goose Folklore(3:33) -- Evidence for Bird Migration (2:23) -- Evidence Against Hibernation (1:59) -- Systematic Bird Ringing (2:52) -- Caterpillar Connection (2:00) -- Maria Sibylla Merian (3:22) -- Round Trip Relay Race (4:16) -- Credits: Magical Appearances: Attenborough's Natural Curiosities, Series 2 (0:44).