Butterflies get it on in weird ways. There were thousands of these guys flying out there, often in little mini-clouds of 6 or 7, chasing each other around, (sort of) weighing down the buckeye. A sight to behold.
The Variable Checkerspot (Euphydryas chalcedona) is noted for the variablility in coloration of it's larvae and adult forms. It also has the name Chalcedon Checkerspot.This one has many more red spots than the one seen at www.flickr.com/photos/alanvernon/5783995434/in/set-721576...Observed in the Coast range mountains of San Luis Obispo county, California.