This is the time of year when another great migration moves through Tehachapi Pass. These mountains mark the southern boundary of the Sierra Nevada, and provide a pathway over the Great Green Wall that forms a natural barrier in California stretching 400 miles long and averaging about 70 miles wide. Currently, the creatures who are migrating through are Painted Lady butterflies.

I've written about these little beauties before, because their yearly migration is part of the rhythm of life in the Tehachapi Mountains. Every year waves of them pass through during warmer days in March or April. I saw the first groups of Painted Ladies (Vanessa cardui) moving through in large numbers on a warmish day on March 7.

They arrive at different times from year to year, always in early spring. Five years ago, one of the biggest days was on April 21, when my friend Steve Shaw counted more than 50 butterflies each minute migrating past the spot on his Tehachapi property where he was watching them.

These pale orange and black butterflies with white highlights are about half the size of Monarch butterflies. While they are not the fastest fliers among butterflies, they can fly quite rapidly, and their stamina and determination is stunning.

Because here is the amazing thing about the Painted Ladies in the U.S. and Canada: pretty much all of them that appear in the spring are originally from Mexico. Though the Painted Lady butterflies can be found in every state and well into Canada by summer, hard frosts in the fall and winter kill them off, with the possible exception of small numbers that may survive in coastal California and extreme southern Arizona.

However, enough adults survive in warmer Mexico to lay abundant eggs, which hatch into caterpillars in January and February in the far Southwest. These caterpillars, which are mostly brown or black with some yellow highlights and short white spines, feed on thistles and other host plants, grow quickly and then form a chrysalis and emerge about 10 days later.

Upon completing their metamorphosis from caterpillars into attractive butterflies, Painted Ladies begin to stream north into the United States. The timing of their flight and the number of butterflies varies from year to year and is influenced by winter temperatures and rainfall. In favorable years like this one appears to be, the total population of Painted Ladies is hard to grasp as untold millions upon millions of these nectar-loving flyers stream north to repopulate the entire United States and Canada.

Unlike the yearly migrations of Monarch (Danaus plexipus) butterflies, the Painted Lady migrations are a one-way trip without a corresponding return in the fall.

Painted Ladies don't fly high above the ground in the region of relative safety used by migrating birds — instead they usually flutter and sail a few feet above the ground, exposing them to many hazards including cars, whose radiators and grills often bear the remains of Painted Ladies that didn't survive an encounter with speeding car or truck. Windshields are mostly just dotted with yellow splats. Butterflies get their common name from the yellow, butter-like color of their body fluid, which is a liquid known as hemolymph.

Sheer numbers enable the species to withstand such carnage and other creatures make use of the bounty of butterflies. I have watched ravens make repeated forays onto Highway 202 or Cherry Lane to retrieve and eat butterflies that had perished in collisions with cars. Painted Ladies don't feed on milkweed plants and so lack the bitter taste imparted to Monarchs, which become unpalatable and thus largely protected from predation.

The annual Painted Lady migration is certainly not a new phenomena, so no doubt it was witnessed by the original Californians for thousands of year before Europeans arrived. Butterflies are a special and cherished design element in Native California basketry by different tribes.

Rosie Marcus Hicks, a talented Nuwä (Kawaiisu or Paiute) weaver who lived in the Sand Canyon area in the early 1900s, created a gorgeous basket featuring four larger butterflies and 20 smaller ones. Did the smaller, more abundant butterflies represent Painted Ladies? We don't know, but Rosie must observed the annual Painted Lady migrations during her life. My friend Cindy Waldman wrote a memorable children's book called The Butterfly Basket that is a historical fiction woven around Rosie's landmark basket, and Sand Canyon in the 1920s. Cindy has recently completed a sequel as well.

Observant local residents in the days ahead will notice that all the butterflies are moving through Tehachapi Pass, from the Mojave Desert in southeast to the San Joaquin Valley in the northwest. Occasionally they alter their course to avoid buildings or natural obstacles, but the Painted Ladies are all basically headed north. I wish them well on their epic journey.

Have a good week.

Jon Hammond has written for Tehachapi News for more than 30 years. Send email to tehachapimtnlover@gmail.com.