It is almost impossible to take a hike in the brushy parts of California in the spring without encountering this butterfly or its caterpillar or both in large numbers. Every roadway seems to be flocking with the adults, while almost every bush monkey flower, or other plants of the figwort family, seem to be crawling with the very spiny dark caterpillars. The bright reddish-brown and white and black marked butterflies gather in myriads at wet places on the road and rise in clouds when you come near. Being neither strong nor intelligent fliers, they are easily caught. Certainly they do not have the dodging ability of a swallowtail or buckeye, nor the hiding ability of a little blue or a wood nymph.
So how are they so successful and exist in such great numbers? There seem to be two possible answers. One is that so many billions of eggs are laid that at least some of the butterflies become adults, and the other is that the butterfly may be more or less poisonous. When some were fed to a pair of monkeys at a zoo, the monkeys were seen to wrinkle their noses and throw the creatures out of the cage in disgust, so this makes it very possible that Chalcedon Checkerspots are either poisonous or have a very bad taste.
The spiny backed caterpillars may cover a monkey flower bush so thickly as to make it almost black, but, when the time comes for each of them to change into a chrysalid, each goes off alone to a secret hiding place, caring no more for the company of its kind.