Skies in Southern California currently resemble a Hitchcock scene – perhaps a little less moody and more ethereal. From Burbank to Redondo Beach to South Central Los Angeles and beyond, butterflies swarm through the air in a feverish dream of disruption and migration. And with the total number of these small butterflies of two to three inches, better known as painted ladies (Vanessa cardui), which appear to be in the region (from around 300,000 in 2017 to 25,000 last year, according to one monitoring program), this magical outburst of lepidoptera & # 39; s brings both wonder and hope.
The fluorescence of the painted woman is the result of an unusually rainy winter in California – and in particular in the deserts, which has also contributed to the flowering of this spring's superbloom. James Danoff-Burg, director of the Living Desert Zoo and Gardens, said in a statement: "The average annual rainfall in the Coachella Valley is five centimeters. This year we had three centimeters of Valentine's Day alone." Art Shapiro, an ecologist at the University of California, Davis, who has been studying butterfly migration since 1972, told CNN that "painted ladies tend to thrive if there is a superbloom because there are so many plants for the butterflies to lay their eggs on and for caterpillars to eat While these butterflies migrate from Mexico through the deserts of Southern California to the Pacific Northwest every year, they usually go relatively unnoticed because there aren't quite many of them.
This year's phenomenon is called an irruption. "The difference is that a migration is a seasonal phenomenon," says Matthew Shepherd of the Xerces Society, a non-profit organization for invertebrates in Portland, Oregon. "A disruption is a sudden and huge increase in population size that does not occur every year. In essence, there is an abundance of something that leads to a population so large that the pressure pushes the butterflies at the edges further and further. flowers. "
Another reason why the critters make their way along the coast of Mexico, where they spend the winter in the Sonora desert, is because of this bustle. "The pressure of having so many butterflies in an area forces them out," says Shepherd. "The mass of host plants that the caterpillars eat is just as important as the availability of nectar to fuel the adults. The butterflies do not leave anything behind, but move in search of plants and areas that are not saturated with other painted ladies! "
A beautiful painted lady in a moment of break. Renee Grayson / (CC BY 2.0)
The small insects that flash through the vistas of California are cousins of the larger and more vibrant monarch, who faced a critically low population in California last year (a drop of 85 percent). Both butterflies are similar in color orange and black with white whispers – and are essential pollinators of state plants. Tom Merriman, director of Vlin-based Butterfly companies in Encinitas, says that butterflies "can end up in flowers that cannot reach bees," and that "princes are considered an indicator species that help us assess the state of our environment "
According to Merriman, an event like this was recently in Southern California in 2005, an El Niño year. (Then I-5 was closed in Southern California because of the amount of dead butterflies on the road, Shepherd says.) That wet year there were an estimated more than a billion painted ladies. Based on the butterflies that flew through Encinitas yesterday, Merriman dares that the region looks just as much. "They go fairly fast and can travel almost 30 miles per hour and can travel up to 100 miles per day," says Merriman. Occasionally the ladies stop sipping nectar from flowers and then continue with their rush.
"Think of cars driving on the highway, they all go in the same direction, but not really together," says Merriman. "We think it will take a few more weeks. They will not be that close – some will no longer have energy and will stop eating and brooding, some will encounter predators, or worse, cars & # 39; s."
The painted ladies are expected to stay wherever they settle during the summer. Shepherd & # 39; s guess is that they will arrive in Oregon sometime in April. They will make offspring, and those who are now flying north will almost certainly be the grandparents in July. For most of them, the Pacific Northwest will be the end of the road. "Painted ladies usually die where they are at the end of the season," says Shepherd, because their average life expectancy is two to four weeks. Then their descendants will travel back to Mexico in the fall.