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