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.

Floris van Breugel / Monarch butterflies (Danaus plexippus) over winter on Eucalyptus and Monterey Cypress trees near Pismo Beach, San Luis, California, USA December.. When temperatures warm up enough, they will embark on...

Heather Angel / Monarch butterflies (Danaus plexippus), three nectaring on Poinsettia (Euphorbia pulcherrima), resting on red bracts. In butterfly house, Xishuangbanna, Yunnan Province, China.

Doc White / Monarch butterfly, (Danaus plexippus), migrating group resting in tree Pismo Beach, California, USA. January.

Doc White / Monarch butterfly, (Danaus plexippus), migrating group resting in tree Pismo Beach, California, USA. January.

Doc White / Monarch butterfly, (Danaus plexippus), migrating group resting in tree Pismo Beach, California, USA. January.

Doc White / Monarch butterfly, (Danaus plexippus), migrating group resting in tree Pismo Beach, California, USA. January.

Derek Galon / Caterpillar of Monarch butterfly (Danaus plexippus) feeding on seed pod of Bloodflower plant ( Asclepias curassavica). Dominica, Eastern Caribbean, Lesser Antilles. Focus stacked photo.

Nick Hawkins / Monarch butterfly (Danaus plexippus) male, migrating North, Anchorage Provincial Park, Grand Manan Island, New Brunswick, Canada, June.

Doug Wechsler / Monarch butterfly ( Danaus plexippus) egg on common milkweed; Philadelphia, Pennsylvania, USA. August.

Lynn M. Stone / Tagged Monarch butterfly (Danaus plexippus) on Dahlia flower, October. Waterford, Connecticut, USA (non-ex)

Nick Hawkins / Monarch butterfly (Danaus plexippus) feeding on Goldenrod, New Brunswick, Canada, September.

Nick Hawkins / Monarch butterfly (Danaus plexippus) emerging from chrysalis, photographed on white. New Brunswick, Canada, September. Sequence 8 of 8

Nick Hawkins / Monarch butterfly (Danaus plexippus) emerging from chrysalis, photographed on white. New Brunswick, Canada, September. Sequence 7 of 8

Nick Hawkins / Monarch butterfly (Danaus plexippus) emerging from chrysalis, photographed on white. New Brunswick, Canada, September. Sequence 6 of 8

Nick Hawkins / Monarch butterfly (Danaus plexippus) emerging from chrysalis, photographed on white. New Brunswick, Canada, September. Sequence 5 of 8

Nick Hawkins / Monarch butterfly (Danaus plexippus) emerging from chrysalis, photographed on white. New Brunswick, Canada, September. Sequence 4 of 8

Nick Hawkins / Monarch butterfly (Danaus plexippus) emerging from chrysalis, photographed on white. New Brunswick, Canada, September. Sequence 3 of 8

Nick Hawkins / Monarch butterfly (Danaus plexippus) emerging from chrysalis, photographed on white. New Brunswick, Canada, September. Sequence 2 of 8

Nick Hawkins / Monarch butterfly (Danaus plexippus) emerging from chrysalis, photographed on white. New Brunswick, Canada, September. Sequence 1 of 8

Kim Taylor / African monarch butterfly (Danaus plexippus). Gambia, Africa

Doug Wechsler / Monarch butterfly caterpillar (Danaus plexippus) close up of skin and spiracle, Philadelphia, USA August

Doug Wechsler / Monarch butterfly caterpillar (Danaus plexippus) close up of proleg and pseudopod, Philadelphia, USA August

Doug Wechsler / Monarch butterfly caterpillar (Danaus plexippus) close up of legs, Philadelphia, USA August

Doug Wechsler / Monarch butterfly caterpillar (Danaus plexippus) Philadelphia, USA September

Rolf Nussbaumer / Monarch (Danaus plexippus), adult feeding on Zinnia flower, Hill Country, Texas, USA. October

Rolf Nussbaumer / Monarch (Danaus plexippus), egg, Hill Country, Texas, USA. October

Rolf Nussbaumer / Monarch (Danaus plexippus), butterfly emerging from chrysalis on Tropical milkweed (Asclepias curassavica) wings unfolding, series, Hill Country, Texas, USA Sequence 18 of 18. October

Rolf Nussbaumer / Monarch (Danaus plexippus), butterfly emerging from chrysalis on Tropical milkweed (Asclepias curassavica) wings unfolding, series, Hill Country, Texas, USA Sequence 17 of 18. October

Rolf Nussbaumer / Monarch (Danaus plexippus), butterfly emerging from chrysalis on Tropical milkweed (Asclepias curassavica) wings unfolding, series, Hill Country, Texas, USA Sequence 16 of 18. October

Rolf Nussbaumer / Monarch (Danaus plexippus), butterfly emerging from chrysalis on Tropical milkweed (Asclepias curassavica) wings unfolding, series, Hill Country, Texas, USA Sequence 15 of 18. October

Rolf Nussbaumer / Monarch (Danaus plexippus), butterfly emerging from chrysalis on Tropical milkweed (Asclepias curassavica) wings unfolding, series, Hill Country, Texas, USA Sequence 14 of 18. October

Rolf Nussbaumer / Monarch (Danaus plexippus), butterfly emerging from chrysalis on Tropical milkweed (Asclepias curassavica) wings unfolding, series, Hill Country, Texas, USA Sequence 13 of 18. October

Rolf Nussbaumer / Monarch (Danaus plexippus), butterfly emerging from chrysalis on Tropical milkweed (Asclepias curassavica) wings unfolding, series, Hill Country, Texas, USA Sequence 12 of 18. October

Rolf Nussbaumer / Monarch (Danaus plexippus), butterfly emerging from chrysalis on Tropical milkweed (Asclepias curassavica), series, Hill Country, Texas, USA Sequence 11 of 18. October

Rolf Nussbaumer / Monarch (Danaus plexippus), butterfly emerging from chrysalis on Tropical milkweed (Asclepias curassavica), series, Hill Country, Texas, USA Sequence 10 of 18. October

Rolf Nussbaumer / Monarch (Danaus plexippus), butterfly emerging from chrysalis on Tropical milkweed (Asclepias curassavica), series, Hill Country, Texas, USA Sequence 9 of 18. October

Rolf Nussbaumer / Monarch (Danaus plexippus), butterfly emerging from chrysalis on Tropical milkweed (Asclepias curassavica), series, Hill Country, Texas, USA Sequence 8 of 18. October

Rolf Nussbaumer / Monarch (Danaus plexippus), butterfly emerging from chrysalis on Tropical milkweed (Asclepias curassavica), series, Hill Country, Texas, USA Sequence 7 of 18. October

Rolf Nussbaumer / Monarch (Danaus plexippus), butterfly emerging from chrysalis on Tropical milkweed (Asclepias curassavica), series, Hill Country, Texas, USA Sequence 6 of 18. October

Rolf Nussbaumer / Monarch (Danaus plexippus), butterfly emerging from chrysalis on Tropical milkweed (Asclepias curassavica), series, Hill Country, Texas, USA Sequence 5 of 18. October

Rolf Nussbaumer / Monarch (Danaus plexippus), butterfly emerging from chrysalis on Tropical milkweed (Asclepias curassavica), series, Hill Country, Texas, USA Sequence 4 of 18. October

Rolf Nussbaumer / Monarch (Danaus plexippus), butterfly emerging from chrysalis on Tropical milkweed (Asclepias curassavica), series, Hill Country, Texas, USA Sequence 3 of 18. October

Rolf Nussbaumer / Monarch (Danaus plexippus), butterfly emerging from chrysalis on Tropical milkweed (Asclepias curassavica), series, Hill Country, Texas, USA Sequence 2 of 18. October

Rolf Nussbaumer / Monarch (Danaus plexippus), butterfly emerging from chrysalis on Tropical milkweed (Asclepias curassavica), series, Hill Country, Texas, USA Sequence 1 of 18. October

Lynn M Stone / Monarch butterfly (Danaus plexippus) nectaring on Purple Loosestrife in wet meadow, East Haddam, Connecticut, USA

Lynn M Stone / Monarch butterfly (Danaus plexippus) female nectaring on a Montauk Daisy, Madison, Connecticut, USA. Non-ex.

Adrian Davies / Monarch butterfly (Danaus plexippus) caterpillar on Milkweed (Asclepias sp) Butterfly House, Devon, England. Captive, occurs in North America.

John Abbott / Wasp (Pteromalus puparum), parasitoid wasp of butterfly pupae including Monarch butterflies (Danaus plexippus) Brackenridge Field Laboratory, Austin, Travis Co, Texas, USA, December.

Michael D. Kern / Monach Butterfly (Danaus plexippus) large group hibernating on a tree, Santa Cruz, California, USA, December.

Tui De Roy / Carpenter Bee (Xylocopa darwinni) and Monarch Butterfly (Danaus plexippus) on Scalesia vilosa flowers. Punta Cormorant, Floreana Island, Galapagos.

Stephen Dalton / Monarch butterfly (Danaus plexippus) male, Florida, USA, February.

Axel Gomille / Large group of Monarch butterflies (Danaus plexippus) drinking from a puddle, El Rosario reserve, Mexico. Wildlife Photographer of the Year Competition 2010 - Highly Commended - Behaviour: Cold Bloode...

Tui De Roy / Monarch butterflies (Danaus plexippus) resting on trees in wintering grounds in the mountains of central Mexico, El Rosario Butterfly Sanctuary, Michoacan, Mexico.

Tui De Roy / Monarch butterflies (Danaus plexippus) covering Fir trees on wintering grounds in the mountains of central Mexico, El Rosario Butterfly Sanctuary, Michoacan, Mexico.

Lucas Bustamante / Monarch butterflies(Danaus plexippus) in flight during migration, Michoacan, Mexico.?? February.

Joel Sartore / Photo Ark / Monarch butterfly (Danaus plexippus) female profile, opening and closing its wings, Lincoln, Nebraska, USA. Controlled conditions.

Joel Sartore / Photo Ark / Monarch butterfly (Danaus plexippus) female close up, moving proboscis, Lincoln, Nebraska, USA. Controlled conditions.

Joel Sartore / Photo Ark / Monarch butterfly (Danaus plexippus) female profile, opening and closing its wings, Lincoln, Nebraska, USA. Controlled conditions.

Joel Sartore / Photo Ark / Monarch butterfly (Danaus plexippus) female opening and closing its wings, Lincoln, Nebraska, USA. Controlled conditions.

Edwin Giesbers / Close up of Monarch butterfly (Danaus plexippus) wing detail. Captive.

Bruce Thomson / Monarch butterfly (Danaus plexippus) feeding on thistle (Asteraceae) flower. Introduced butterfly established in temperate and subtropical regions, Bunya Pine Mountains National Park, Queensland, Aust...

John Chan / Monarch Butterfly (Danaus plexippus) nectaring on a Sweet scabious (Scabiosa atropurpurea) before flying away, Orange County, California, USA, May.

John Chan / Monarch Butterfly (Danaus plexippus) nectaring on a Sweet scabious (Scabiosa atropurpurea), Orange County, California, USA, May.

Carlos Zorrilla / Monarch butterfly (Danaus plexippus) resting on coffee (Coffea arabica) berries, Ecuador.

John Chan / Monarch butterfly (Danaus plexippus) taking flight from a Pride of madeira (Echium candicans) after contact with a Honey bee (Apis mellifera), Southern California, USA, April.

John Chan / Monarch butterfly (Danaus plexippus) feeding from a Pride of Madeira (Echium candicans), Southern California, USA, April.

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.

Patricio Robles Gil / Monarch butterfly (Danaus plexippus) mural on hotel, Agangeo Town near to Monarch Butterfly Reserve, Mexico.

Patricio Robles Gil / Monarch butterfly (Danaus plexippus) group, silhoutted some flying and some resting in oyamel trees, Reserve el Rosario Sanctuary, Mexico.

Patricio Robles Gil / Monarch butterfly (Danaus plexippus) some flying and some resting in oyamel trees, El Rosario Sanctuary Reserve, Mexico.

Patricio Robles Gil / Monarch butterflies (Danaus plexippus) in flight, El Rosario Sanctuary, Mexico, November.

Patricio Robles Gil / Mural of Monarch butterfly (Danaus plexippus), in Agangeo town, near Monarch butterfly reserve, Mexico

Patricio Robles Gil / Mural of girl with Monarch butterfly (Danaus plexippus) wings in Agangeo town, near to Monarch butterfly reserve, Mexico.

Patricio Robles Gil / Monarch butterfly (Danaus plexippus) Sierra Chincua Sanctuary, Mexico.

Rolf Nussbaumer / Monarch butterfly (Danaus plexippus) caterpillar pupa on Aquatic milkweed (Asclepias perennis). Hill Country, Texas, USA. Sequence 6/6.

Rolf Nussbaumer / Monarch butterfly (Danaus plexippus) caterpillar pupating on Aquatic milkweed (Asclepias perennis). Hill Country, Texas, USA. Sequence 5/6.

Rolf Nussbaumer / Monarch butterfly (Danaus plexippus) caterpillar pupating on Aquatic milkweed (Asclepias perennis). Hill Country, Texas, USA. Sequence 4/6.

Rolf Nussbaumer / Monarch butterfly (Danaus plexippus) caterpillar pupating on Aquatic milkweed (Asclepias perennis). Hill Country, Texas, USA. Sequence 3/6.

Rolf Nussbaumer / Monarch butterfly (Danaus plexippus) caterpillar pupating on Aquatic milkweed (Asclepias perennis). Hill Country, Texas, USA. Sequence 2/6.

Rolf Nussbaumer / Monarch butterfly (Danaus plexippus) caterpillar starting to pupate on Aquatic milkweed (Asclepias perennis). Hill Country, Texas, USA. Sequence 1/6.

Rolf Nussbaumer / Monarch butterfly (Danaus plexippus) caterpillars feeding on Aquatic milkweed (Asclepias perennis). Hill Country, Texas, USA.

Lynn M. Stone / Monarch butterfly (Danaus plexippus) pair mating on Swamp milkweed (Asclepias incarnata). Connecticut, USA. August.

Lynn M. Stone / Monarch butterfly (Danaus plexippus) nectaring. Madison, Connecticut, USA, September.

Lucas Bustamante / Monarch butterflies (Danaus plexippus) flying during a warm morning. When the overwintering period draws to an end large numbers become active. Michoacan, Mexico, February.

Derek Galon / Timelapse of a Monarch butterfly (Danaus plexippus) caterpillar feeding on Mexican butterfly weed (Asclepias curassavica), Dominica, Lesser Antilles.