In 2012, a crop of California's most prized ornamental trees was overrun by an invisible invader. The growing shoots of coral beans -- the official city tree of Los Angeles -- began wilting and falling away, revealing stems that had been hollowed out from the inside by the caterpillars of Erythrina stem borer moths. A new study published this Wednesday in the Journal of Applied Entomology reveals the culprit's origin through a DNA analysis of insects provided by the late Dan Lindsley, formerly a retired UC San Diego professor of genetics.