I drove down to Ridgecrest last week hoping to check out the wildflowers. While I did eventually get to see some great blooms, I had to stop a couple times to clear off my windshield which looked something like this:

In March the annual northern migration of painted lady butterflies (Vanessa cardui) had arrived in southern California, eventually arriving in our area. No doubt you have seen those that didn't collide with my windshield in great numbers on fruit tree blossoms and and other blooms.

This is a annual event, but according to Dr. Art Shapiro their numbers are huge on years that have large wildflower blooms. The last major large migration was in 2005. 

The Eastern Sierra is a favored path for their travels to the Pacific Northwest. It will take several generations of the butterflies to make it northward, and then the process will repeat in the autumn when they return to Texas and Mexico for the winter.

NBC News down south did a piece on these butterflies. You can see it here.

I always find these mass migrations of insects interesting. I am glad that in this case it's something harmless and beautiful.