'Rocky Mountain' Phoebus Parnassian (Parnassius phoebus smintheus)

This large butterfly looks like the very common and smaller Checkered White (Pontia protodice) in flight, the largest size is noticeable. They tend to land on the ground often. I found them very hard to find on the bare ground, they camouflage very well. In fact I saw about 40 of them land on the ground and only found 2 without kicking them up with my approach. Most of the time they were underfoot and I just couldn't see them! These yellow flowers are Stonecrop the host plant, it is quite common in Colorado. Usually you have to be at about 8000 foot or more to find these parnassins and they are found of hill topping.