Dozens of monarch butterflies glide from one branch to the next at Shelter Gardens in preparation for their long trip south. The sound of crickets and the smell of freshly mowed grass and flowers provide the backdrop for this midday meal for the monarchs as they pass through Missouri to their wintering grounds in the southern Sierra Madre near Mexico City.
The Leucothoe fontanesiana bush, commonly called “Girard’s Rainbow,” seems to be the favorite of the orange-and-black butterflies, said Joy Long, superintendent of the Shelter Gardens ground crew.
“Yesterday was the biggest day I have seen,” Long said. “There were clusters of them flying overhead, and the flowering bushes were covered.”
Long said she first noticed the monarchs on her way back from a trip to South Carolina with her husband, John, a couple of weeks ago. Once she returned to Columbia, she couldn’t believe how many they saw.
“It was just an amazing thing for us,” Long said.
The monarchs travel on one of three major flyways, much like migrating birds. One of those flyways passes over Missouri.
Long said her husband has been researching the migration on the Internet and has been coming home with monarch trivia every night.
“It takes two to three generations of butterflies to get from (Mexico) to northern America and then only one generation to get all the way back,” Long said. “Also, by the way the sun comes up and circles over the butterfly while in the cocoon or chrysalis, it programs into the butterfly which direction to fly when it emerges. Isn’t that awesome?”
Kevin Lohrass, program director for the Runge Nature Center, said the monarchs will be migrating through mid-Missouri for about three more weeks, with the peak of the migration this week or next. He said the number of monarchs migrating in this flyway is estimated at 30 million.
The butterflies know when to leave their northern homes after the shortened daylight hours and colder temperatures of the fall months lower the level of a certain hormone. This initiates a standstill in their reproductive cycle and stimulates them to fly south, MU associate entomology professor Richard Houseman said.
The butterflies control direction during their 3,000-mile journey by adjusting their flight by the light of the sun. When they begin, they will fly directly south while adjusting their flight path by about one degree per day. After 45 days, they will be headed southwest on a path that will take them to their roosting areas in Mexico. They determine the wind’s direction by sensing it differently on one side of their bodies than the other, Houseman said.
In mid-March, the temperature change will signal the butterflies to begin flying again, and they will travel to the Gulf Coast states to mate and lay eggs that produce the caterpillars that become butterflies. After mating, the fall generation will die off and the spring generation will continue the journey north, Houseman said. Generations will change once or twice more before the following autumn, when a new migration will begin.