A Comprehensive Guide to the Viceroy Butterfly (Limenitis archippus)
The Viceroy butterfly looks a lot like the Monarch Butterfly. Similar to the Monarch it is also distasteful to predators. The Viceroy is found in most of North America, but may not be in California (Wikipedia). The Viceroy feeds on willows (Salix sp.) and members of the Populus genus including cottonwoods.