By Kate Linthicum Los Angeles Times EJIDO LA MESA, Mexico — As a boy, Francisco Ramirez Cruz loved hiking with his grandfather up into the mountains of central Mexico. While the old man grazed sheep or hunted for wild mushrooms, Ramirez would play amid the throngs of monarch butterflies that migrated 3,000 miles to this forest each autumn, turning the blue sky into a sea of orange. Ramirez is 75 now,