Monarch butterflies are not unique to the United States and Mexico ; they can be found on all five continents, anywhere milkweed grows. Because they feed on milkweed, which contains certain toxins, Monarchs are poisonous both as caterpillar and as butterfly; they therefore know few predators. Monarchs are one of the few insects that migrate (round-trip) once in their lifetime. Migrating Monarchs can fly up to 3,000 miles one way to their roosting area. The Monarchs butterfly is a tropical animal yet it is found as far north as James Bay in Canada during the summer season. Not all Monarchs butterflies migrate. The later summer Monarch larvae are the migrating butterflies. Spring and summer butterflies do not undertake migration. Non-migrating Monarchs live about 4 weeks. Migrating Monarchs live 7 to 12 times longer. Once they have undertaken the journey back from the roosting area, migrating Monarchs have only 4 weeks to live. Late summer butterflies experience diapause, or delayed sexual maturity: sexual organs only develop the following spring. Each fall, the Monarchs undertake a massive migration from Canada and Northern United States to a particular forested mountain in Central Mexico , the Oyamel fir Forests. The Oyamel fir Forests are located in the high mountains in the state of Michoacan in Mexico , which runs from the transvolcanic mountains west of Mexico City to the Pacific Ocean (location map of the Michoacan state in Mexico http://lexis.pop.upenn.edu/mexmig/mexmaps/michoacan/michoacanpage1.htm). The Monarchs roosting areas have been preserved in t wo sanctuaries: El Rosario Butterfly Sanctuary and the Sierra Chincua Sanctuary. The nearest cities to the sanctuaries are Angangeo.and Zitacuaro. The Sanctuary Reserve boundaries have been increased in 2000. The Oyamel fir forests exhibit certain characteristics necessary for the Monarchs' optimal overwintering conditions: They stand at 3000 meters (about 10,000 feet) above sea level, on steep, southwest-facing slopes. The cold temperatures are close to but not quite freezing for energy conservation. The trees are important: Oyamel fir trees have a lot of pine needles necessary for good adherence when roosting. The forest must be thick with many, close surrounding trees for protection from wind and snow. The Monarchs need fog and clouds for moisture. The butterflies also need access to nearby streams for quick hydration when weather permits (when it warms up a bit) Timeline for migration: The Monarch migration is closely related to change in seasons. As soon as the Monarch larva hatches (Late August-September) the autumn butterfly starts to migrate. The migrating butterfly stops only to feed and rest at night. It reaches its destination in Michoacan by the end of November. It hibernates until the end of February-beginning of March. It then mates and starts the journey north again The Monarch females lay eggs on milkweed plants in Southern U.S as they migrate back north, starting the life cycle of the Monarchs once again.