Associated Press With help from weather, butterflies return on trip north
BOZEMAN (AP) - They're back.
Aided by strong desert rains in the Southwest and high winds, Painted Lady butterflies have retuned to Bozeman, in droves.
The migratory insects began their journey in northern Mexico, and weather patterns have helped them fly this far north, said Will Lanier, a research specialist in the Montana State University entomology department.
"The migration pattern is that they are basically blown up from the south," Lanier said.
Storms give the insects a boost, Lanier said.
Although powerful winds probably took their toll on the butterflies, many were able to surf along in front of the storm, he said.
The Painted Lady is one of the most abundant butterflies in the world, but the last notable migration in Bozeman was in 1991, with a smaller one in 1995, Lanier added.
"A few make it up this far every year," he said. "This year there's clouds and clouds of them. … They'll go all the way to northern Alberta."
Lanier explained that adult Painted Ladies mate to produce eggs, which hatch into caterpillars. The caterpillars mostly feed on thistles, he said, and since weather in the desert was good for thistles this year, the larvae have had an abundant food source.
Jerry Cashman of Cashman Nursery remembers the 1991 migration, and the resulting number of caterpillars. To keep the insects from feasting on trees, people painted an oily substance called "tree tangle" on the trunks.
"You can still see rings around trees around town where people did that," he said.
Lanier said the Painted Lady larvae prefer the thistle plant to trees, and people shouldn't worry about the caterpillars damaging their plants.
"A plant produces a lot more foliage than it needs to survive," he said. "The butterfly larvae doesn't eat enough to kill it."