Monarch Butterflies on the move

Over the next several weeks, many of us will be keeping an eye out for migrating monarch butterflies heading south to spend the winter in Central Mexico forests.

The monarch’s long, arduous trek in the fall makes the beautiful orange and black creature a source of wonder among nature lovers and scientists alike.

According to the US Forest Service, the annual migration of North America’s monarch butterfly is a unique and amazing phenomenon. The monarch is the only butterfly known to make a two-way migration as birds do. Unlike other butterflies that can overwinter as larvae, pupae, or even as adults in some species, monarchs cannot survive in northern climates.

Using environmental cues, the monarchs know when it is time to travel south for the winter. Monarchs use a combination of air currents and thermals to travel long distances. Some fly as far as 3,000 miles to reach their winter home.

Their average lifespan is about one to three months, raising about four or five generations each summer depending on geographic location.

“As monarchs migrate north in the spring, they lay eggs and die,” said Mark Howery, wildlife diversity senior biologist for ODWC. “The next generation will repeat that cycle moving farther north, and then the last generation makes the southward migration and the beginning of the spring migration northward, living for about six months.”

The last generation for the summer will live from about August to May as it overwinters from California to Mexico.

“As monarchs migrate, they will congregate in large groups and rest on the leeward side of trees to warm their bodies in the mornings before taking flight,” said Howery. “It is such a beautiful site if you happen to catch them gliding on a tail wind coming from the north.”

Other migratory butterflies remain active as they winter south of the United States’ border. However, monarchs go into a state of inactivity, thus they do not reproduce or feed. They can often be found in large groups resting on trees during this time.

Monarch caterpillars, larva, feed on various milkweed plants.

“The milkweed family has bitter, somewhat toxic alkaloids in their milky sap,” said Howery. “As caterpillars transform into butterflies, the monarchs’ body deposits this toxin beneath its skin and it is pumped into the wings and body. This keeps birds from eating them when resting on trees.”

The last monarchs that completed their migration will come out of their torpor state and head north as the weather warms again. Then, they will begin laying eggs and continue the cycle again.

Monarchs are one of the most highly recognized butterflies with their orange upperside and black-lined veins. Their average wingspan is about four inches, making them quite large butterflies.

So keep your eyes open for these migration giants of the insect world this fall.