By the time
they all converge in the transverse Neo-Volcanic Mountain Range
in Mexico, there are millions flying together, perhaps as their
ancestors have for millennium. They start arriving on the first
of November, at the same time as the national festival of Los Dias
de Muertos, Days of the Dead. The local people believe the monarchs
are old souls returning to the sacred mountains.
Here, at altitudes
of 9,000 to 12,000 feet, they overwinter, roosting in oyamel trees
at night in groups estimated to be hundreds of thousands strong
per tree. In the warmth of the morning sun, they fly low, landing
to drink the morning dew and dampened earth near natural springs.
As the sun moves higher, they flights are more energetic, millions
of golden fluttering wings rustling the air in the sound and beauty
of ever changing patterns of movement.
As spring approaches,
the monarchs mate and by the end of March, they head north. Searching
out the choicest milkweeds, each female will oviposit about 400
eggs. Her life cycle will then end. Only one to two percent of the
caterpillars will survive. These caterpillars mature into butterflies
who continue their parents northward migration. It can take
as many as three or four generations to re-colonize the entire northern
habitat range. The summer monarchs complete their life in about
three weeks. The monarchs born in autumn have a life cycle of about
ten months. In September, they begin their southward migration,
as their ancestors have for time immemorial.