Both Northern and Southern Catalpa trees originally were found in a very limited native range. They were widely planted outside their historic areas for their value as a fast growing tree, for railroad ties, for fence posts and their ornamental value with abundant large flower blossoms. Catalpa trees and catalpa "worms" coevolved together. The catalpa worms are actually insects, larva or caterpillars of the Catalpa Sphinx moth. The adult is a unremarkable brown moth but the large caterpillars have striking yellow sides and jet black stripe down their backs.
No other caterpillar feeds on Catalpa trees and the caterpillars in turn only feed on Catalpa trees. The caterpillars seem to have boom and bust cycles, few or no caterpillars one year and complete defoliation of the tree in another. Learn more about both the trees and these insects with hands-on close-up video of both tree and insect.
