Migrating Butterflies Love Rabbitbrush

"Kathy, I was at your plant walk Saturday at Devil's Backbone and today, there are hundreds, maybe thousands of butterflies there!"

I'd just picked up the phone in mid morning, Sept. 22. To be alerted by Sandy to the butterfly migration.

I'd read something about a butterfly migration in the Denver Post : more than the usual number of painted lady butterflies moving south along the Colorado Front Range.

I went to see for myself.



I was at Devil's Backbone Open Space about 11 on a warm sunny morning.

There are other things in bloom, but rabbitbrush (Ericameria nauseosa see blog) dominates right now.

rabbitbrush

And the butterflies love it.

These are painted lady butterflies, Vanessa cardui. Painted ladies are relatively common and large butterflies with distinctive black spots (eye spots). Found all over the world, their caterpillars especially like to eat weeds such as thistles. They eat plants related to thistles, which would be asters and sunflowers and their relatives, and sometimes even things as different soybeans--they wouldn't be all over the world if they were restricted in what they eat--but thistles are preferred.

The adult butterflies feed on nectar from flowers. So with the rabbitbrush in full bloom they were all over it, storing energy for their migration. They leave northern Colorado to winter in the warmth of the southwestern deserts.

I didn't see hundreds, dozens certainly. But I didn't wander very far either.  The painted ladies were numerous enough to get three and more in a photo with no particular effort.

In addition, there were monarch butterflies, Danaus plexippus, amid the painted ladies. Monarchs are the big black, red and white butterflies, native only to North America, whose numbers have been down lately. Monarchs migrate through Colorado in small numbers: it is always a treat to see one.

monarch butterfly on rabbitbrush

monarch butterfly on rabbitbrush

The butterflies were getting a good meal, and as they did, they carried pollen between one rabbitbrush flower and the next, pollinating the flowers. That's mutualism: both species benefit from the interaction.

It was wonderful, butterflies fluttering all around the deep yellow rabbitbrush flowers. 

Painted lady butterfly on rabbitbrush

Wander where the rabbitbrush is flowering: you'll certainly see honey bees, but likely also painted ladies and monarchs!

Comments and corrections welcome.

Read more
Associated Press. Sept. 21, 2017. Colorado painted orange by large butterfly migration. link
A Wandering Botanist. Milkweeds, Monarch Butterflies and Colorado. link
A Wandering Botanist. Rubber Rabbitbrush--Painting the Landscape Gold link
Worthington, Danika. Sept. 20, 2017. Painted ladies butterflies have taken over the Front Range on their way south Denver Post

Kathy Keeler, A Wandering Botanist

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