The boulders you can see in the this photograph were most likely deposited by glaciers quite some time ago. Boulders like these are pretty common throughout the glacially carved valleys and meadows in Yellowstone National Park.
Zebra Swallowtail Among Arrowleaf Balsamroot
Hiking past a large patch of Arrowleaf Balsamroot, I noticed a Zebra Swallowtail drifting from flower to flower collecting nectar and unwittingly spreading pollen in the process.