All across Canada, in the northeastern United States and in the Midwest, people have reported seeing scores of Painted Lady butterflies (Vanessa cardui).

In fact, the National Weather Service posted an image of a bewildering blob this week of a great mass of colors spread across Denver and neighboring counties. Weather scientists weren’t sure what to make of it. At first, their best theory was that they were looking at birds. But it turns out that it was migrating Painted Lady butterflies.

A radar image that shows migrating Painted Lady butterflies. (National Weather Service)

Todd Stout, of Raising Butterflies, said, “We are experiencing an unprecedented southward fall migration of the Painted Lady butterfly. In all the 30 years I’ve been studying butterflies in Utah, I have never seen anything like this–not in the fall. It is even more pronounced east of us in Colorado and the midwestern states. Yes, Painted Ladies migrate north into Utah from Mexico during the late winter/early spring. This is well documented and well known amongst local butterfly lovers.”

Painted Lady butterflies nectaring on Butterfly Bush (Buddleia spp.).

The Painted Lady is native throughout the United States. In fact, it is the most widely-distributed butterfly in the world. It is found throughout Europe, Asia, Africa, North America, and Central America. It is not a permanent resident in the eastern United States, but quasi-periodically migrates there from the deserts of the southwestern U.S. and northern Mexico. These migrations are sporadic, sometimes enormous, and often follow rainy periods in those deserts.

Painted Lady larvae feed on a wide variety of host plants from the families Compositae (especially thistles), Boraginaceae, Malvaceae (especially the hollyhock Alcea rosea), common mallow (Malva neglecta), and a number of legumes including Iowa soybeans.

The Painted Lady butterfly and some of its host plants.

Some confuse these butterflies with the Monarch (Danaus plexippus). While their color scheme may be similar to Monarch butterflies, Painted Ladies have eyespots on the underside their wings in addition to brown coloring on both sides. Painted ladies lack the vein pattern that monarchs are best known for. Painted ladies are also smaller than Monarchs, with a wingspan measuring less than 3 inches.

Dorsal and ventral views of the Painted Lady. Note the yellow-tipped knobs on their antennae.

Thanks to favorable temperatures, there has been a huge influx of Painted Lady butterflies this fall. Some observers have spotted more than 100 in a single garden! To attract these and other butterflies to your garden you can hang up fruit inside a suet feeder.

A couple of Painted Lady butterflies enjoy sips of sweet fruit juice on a summer afternoon. • Click Here or on photo to view a variety of suet baskets.

Enjoy the butterflies!