The Quino Checkerspot, Euphydryas editha quino, is on the Endangered Species list and is a very rare sighting. It currently flies on a fraction of the open land it once did thanks to ever-increasing development in Southern California, and many of its known haunts are closed to the public. So I was really happy - and surprised - to see two or three fly through while I was in the Otay Wilderness area on March 20, 2010.
Quino Checkerspot, same hike (may be same individual as above). In about four hours in their habitat I saw just two or three Quino Checkerspots, and then only briefly. The plantain in these photographs is a host plant for this butterfly.
Ventral of Euphydryas editha quino
, same day as above. This mountainous area is just north of the border with Mexico. Here is an important paper
on this checkerspot.