2 September 2026
For insect novices like me, August is the easiest time of year to find any life phase of the catalpa sphinx moth (Ceratomia catalpae). In August the caterpillars are large and their bodies signal that it’s time to stop eating and start pupating. They drop from the trees and burrow underground to overwinter and pupate. That’s where I found the caterpillar pictured at top in early August.
How did he reach that stage? Here are some of the steps in his transformation.
1. His parents pupated and emerged in April or May. They are well camouflaged in the woods but not as interesting as the last instar.
2. His mother looked for a catalpa tree and laid her eggs on the undersides of the leaves.
3. By June in Pittsburgh northern catalpas (Catalpa speciosa) are in bloom and already have eggs and caterpillars under their leaves.
4. When they hatch the caterpillars a very pale but they do have that distinctive black horn.
5. In early August in the final (or near final) instar they have yellow sides, a black back and, yes, the black horn.
At this point their damage on the catalpa leaves is obvious.
6. The final instar burrows underground and forms a cocoon — which I never see because I don’t go digging for them. The cocoon waits until spring to emerge as an adult.
And then the cycle starts over again.
Meanwhile this tree in Schenley Park saw no catalpa sphinx moths this year. It went through its own transformation from flowers in June to long seed pods in August.
