A magnificent migration of painted ladies

If you’ve spent any time outside in the last few weeks, you’ve probably noticed a greater than normal number of butterflies flitting past. You’ve been privileged to witness the largest migration of painted lady butterflies in nearly 15 years.

This miracle of nature was spawned by heavier than average winter and spring rainfall in the deserts of the southwestern U.S. and northern Mexico. That rainfall triggered abundant plant growth and a “superbloom” of desert-region plants, which in turn encouraged an explosion in the population of the painted lady butterflies that rely on these plants.

Millions of painted ladies are now migrating from their starting points through California to locations in the northwest U.S.: Oregon, Washington, and some even as far as Alaska. It’s an unimaginably long journey for such a small and seemingly delicate creature. 

Professor Arthur Shapiro from the Department of Evolution and Ecology at the University of California at Davis has studied butterfly migration for decades. He explains that the entire North American population of painted ladies butterflies migrates to the deserts of southeast California, West Texas and northern Mexico during the winter. When the caterpillars hatch, they feed on the local annual plants. Once they transform into adult butterflies, they begin flying north. They can live up to six weeks, but most don’t live that long. There are waves of migration: the first generation flies to northern California; the butterflies stop to breed; and the next generation(s) continue the journey to the Pacific Northwest.

These butterflies tend to fly low and fast (up to 25 mph), hugging open fields and flying sharply up and down to clear obstacles in their way. Their erratic flight is even more attention getting when their numbers are so great. A reserve of abdominal fat fuels each butterfly’s travel, and the insect stops to reproduce only when that energy source is expended.

Painted ladies scientific name Vanessa cardui – are gorgeous butterflies. Their predominant color is orange, but both the upper and lower surfaces of their wings are vibrantly and intricately patterned with other colors including white, black, grey, and shades of brown from tan to rust. 

Painted lady butterfly (Vanessa cardui) feeding from rosemary flowers (Photo © Kathy Ikeda)

Swarms of these beautiful butterflies first arrived at my neighborhood on March 22. That morning, a friend and I travelled to CalExpo in Sacramento for a special visit to the San Francisco Flower and Garden Show; by the time we returned to Stockton in the afternoon, countless painted ladies were fluttering down the streets, through yards, and over houses. It was an incredible and jaw-dropping sight.

The number of migrating painted ladies has decreased since then, but on calm sunny days many of these showy butterflies can still be seen in flight, stopping occasionally to rest.

For nearly three weeks, painted ladies have been visiting my garden to have a drink and take a breather before moving on. It’s been rewarding to watch them eagerly sip nectar from flowers and sun themselves with open wings. They seem especially attracted to the rosemary plants in full bloom (especially the Tuscan Blue variety) and the Bees’ Bliss sage (a California native Salviahybrid). 

And now, a bit of science.

Butterflies can be broadly grouped into two categories: generalists and specialists. Generalists are those types of butterflies whose caterpillars eat the leaves of a variety of different plants. Specialists, on the other hand, are butterflies whose caterpillars rely on a single kind of “host plant” for their food. (Adult butterflies, the pretty flying insects we so love, don’t factor into this categorization because they sip nectar from many species of flowers.)

The painted lady butterfly is a generalist, since its caterpillars can feed on many different plants; they favor plants in the mallow, thistle, and borage families. On the other hand, some of our most common native butterflies are specialists. The iconic monarch butterfly (Danaus plexippus)is the best-known specialist; its caterpillars only eat leaves of milkweed plants (Asclepiasspecies). Caterpillars of the stunning, iridescent, blue-black pipevine swallowtail (Battus philenor)feed only on leaves of pipevine plants (Aristolochiaspecies). 

Unfortunately, the fact that painted ladies are thriving this year doesn’t mean that other native butterfly species are faring well. Many butterfly species, including monarchs, are in serious decline. Habitat loss, pesticide use, and climate change all pose serious threats to the survival of butterflies and other pollinating insects.

You can help to reverse this sad trend by using ecologically safe gardening practices and filling your garden with butterfly-friendly plants. Nectar-rich flowers preferred by adult butterflies include a variety of California natives (asters, buckwheats, coyote mint, goldenrods, milkweeds, salvias, sunflowers) and introduced landscape plants (butterfly bush, cosmos, lantana, lavender, lilac, marigolds, pincushion flower, and rosemary).

Planting a garden to attract and nourish butterflies can be a rewarding experience. When you choose plants specifically to encourage butterflies and other pollinators, it helps restore lost natural environment and results in a garden with an assortment of beautiful plants and year-round bloom. What could be better? 

A few excellent resources for the budding butterfly gardener are:

For gardening-related questions, call the UC Master Gardener office at 209-953-6112, or visit our website.

This entry was posted in Uncategorized. Bookmark the permalink. Post a comment

Post a Comment

You must be logged in to post a comment.

We reserve the right to remove any content at any time from this Community, including without limitation if it violates the Community Rules. We ask that you report content that you in good faith believe violates the above rules by clicking the Flag link next to the offending comment or fill out this form.
  • Categories

  • Archives