The monarch butterflies you see in the fall in Missouri are long distance travelers, biologically and behaviorally adapted to make the long flight to the same mountain forest in Mexico where their ancestors spent the winter.
Monarchs are the only butterfly known to migrate long distance and roundtrip. It takes four generations to complete the journey and this fourth generation will live the longest and travel the whole distance to Mexico. They will neither mate nor lay eggs until their spring return, conserving their strength for the more than 2,000 mile flight. The monarchs' innate ability to integrate the time of day and the sun's location in the sky is a modern navigation marvel. Their large complex eyes monitor the sun's position in the sky and their internal clock is centered in the antennae. Eyes and antennae send information to the brain. Scientists and engineers at Michigan and Massachusetts universities believe they are close to cracking how this information is processed by monarchs travelling to the same destination year after year.
Monarchs will stop to fuel up on nectar along the way to last through winter. They will ride air currents to conserve energy. In the spring, they begin the journey back north through successive generations. This return trip requires milkweed plants. These are the only plants where monarchs will lay their eggs and hatching caterpillars will feed. Their children’s grandchildren, the fourth generation, will make the return trip the following fall.
The monarch migration is a natural wonder, yet their numbers are in serious decline from weather events, habitat loss and other factors. You can help by planting native milkweed plants and other nectar sources in backyards or back forties, at schools, businesses, parks, roadsides and other open places.
For more on making a Monarch habitat, visit MDC’s website.