When I was hiking around Palmyra Cove last Sunday, I came across several Catalpa trees that were rife with large caterpillars. And most of those caterpillars were rife with something else - little eggs all over their bodies. It was amazing to see the extent some of these caterpillars were 'infected' - I didn't spend much time, but one example had over 100 egg sacs on it.

Catalpa Sphinx caterpillars are most often parasitized by small Braconid wasps, Apanteles congregatus. These wasps lay their eggs on the caterpillar, and the larva then feed on the caterpillar until they are ready to hatch, at which time they form small egg sacs where they pupate. According to what I could find, the caterpillars do not survive this infestation, but the ones with large numbers of egg sacs seemed to be moving along just fine.

In fact, I saw very few dead caterpillars - or those that were free of obvious infection. I would say of the 50-60 caterpillars I found, only 2 or 3 were not showing signs of Apanteles congregatus parasitism.