Sylvain Cordier / Monarch butterfly (Danaus plexippus) wintering in Oyamel pine forests (Abies religiosa) Monarch Butterfly Biosphere Reserve / Reserva de Biosfera de la Mariposa Monarca UNESCO World Heritage Site, An...

Sylvain Cordier / Monarch butterfly (Danaus plexippus), wintering from November to March in Oyamel pine forests (Abies religiosa) Monarch Butterfly Biosphere Reserve, Mexico.

Ingo Arndt / Oyamel fir trees (Abies religiosa) growing in pots in nursery for a reforestation programme to replant after illegal logging has destroyed areas of mountain forests where Monarch butterflies (Danaus p...

Claudio Contreras / Monarch butterfly (Danaus plexippus) hibernating in Sacred Fir (Abies religiosa) forest, Mariposa Monarca Special Biosphere Reserve, central Mexico, January.

Claudio Contreras / Hibernating Monarch butterflies (Danaus plexippus) on Oyamel fir trees (Abies religiosa), El Zacatal Colony, Monarch Butterfly Sanctuary, Mexico, December 1996

Claudio Contreras / Colony of Monarch butterflies (Danaus plexippus) hibernating on Oyamel fir trees (Abies religiosa) El Zacatal Colony, Monarch Butterfly Sanctuary, Mexico, December 1996

Patricio Robles Gil / Monarch butterfly (Danaus plexippus) large groups of butterflies hanging from Oyamel branches, Sierra Chincua Sanctuary, Mexico.

Patricio Robles Gil / Oyamel tree full of Monarch butterflies (Danaus plexippus) in fog, Sierra Chincua Sanctuary, Mexico.

Patricio Robles Gil / Oyamel tree full of Monarch butterflies (Danaus plexippus) in fog, Sierra Chincua Sanctuary, Mexico.