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To Phil Helsel
Southern California is known for its annual migration of everything on the move of butterflies as the painted lady. In recent days, the sky has been filled in some areas with the winged creatures.
People used social media to document insects fluttering in California. The butterflies travel from the deserts of Mexico and fly as long as their fat reserves persist before breeding. Generations of insects can reach as far as the Pacific Northwest.
"We were waiting for them to come here, but they have not come up yet," said Arthur M. Shapiro, a professor at the University of California, Davis' Department of Evolution and Ecology, College of Biological Sciences in near Sacramento.
"The years of vast wildflower blossoms are usually really big painted ladies' years," he added, adding the last really big one was 2005 with an estimated billion butterflies.
Shapiro said he received reports of the butterflies vanessa cardui in Temecula, north of San Diego, and in the Anza-Borrego Desert State Park in Pasadena and the Coachella Valley.
The entire North American population of painted butterfly butterflies migrates to West Texas and northern Mexico in the winter. As caterpillars they feed on annual desert plants – their favorites are the families of mallows, boragens and thistles and their relatives – and once they are butterflies, they move north.
They can live up to six weeks, but most do not live it that long There will be migration waves when the first generation comes to Northern California, they breed and then the next generation makes the trip to the Pacific Northwest, said Shapiro.
On the way back, the next generations of butterflies will begin their journey south. In Calfornia, the largest number of butterflies is expected on the eastern side of the Sierra Nevada, Shapiro said.
"The south side is never as big as a big migration from the north," he said.
A similar phenomenon occurs In Europe, some of the butterflies traveled south through the Sahara in Africa and others to Ethiopia and Eritrea, and then migration begins north of the Mediterranean.
Painted butterflies can travel fast. "You can drive cars at a speed of 40 km / h," said Shapiro.
And they can create body heat through muscle contractions, allowing them to fly at lower temperatures. The painted ladies have the highest observed altitude record time in all butterflies at around 22,000 feet.
The size of the northern migrations is often tied to the flowers of wildflowers in the desert, as heavy rains there contribute to the growth of host plants, said Shapiro. The Anza-Borrego Desert State Park said this week that there are great wildflowers in many parts of the park.
Few bird species actually catch the butterflies on the wing. Most are eaten when they are cold or flying slowly or in mud puddles on the ground, he said. And numbers are on the side of the butterflies. "The birds that eat butterflies get very fast," he said.
"Yesterday, March 11, was the anniversary when the front line reached Davis in 2005," said Shapiro. "I thought it would be really cute if they arrived that same day, but it did not happen."