Painted Lady butterflies, some of about 1 billion who are swarming through the skies of southern California during their migration north from Mexico, feed on apple blossom flowers in Glendale, California, March 13, 2019. - Scientists say the migration isn not new, but they have not seen numbers like this in almost 15 years, attributing the event to the unusual amount of rain in the region is year. (Photo by Robyn Beck / AFP)