TOP PHOTO: Early instar orange-striped oakworm caterpillars go to work on red oak leaves.
It’s that time of year again when oakworms do their best to defoliate the red and willow oaks here at the museum. There may be thousands of these voracious moth larvae in the oak trees here at the museum but they never do as much damage as to harm the trees in any great manner. The trees seem to thrive regardless of the devouring hordes of caterpillars relentlessly munching on their leaves.
It often comes up in the lepidopteran literature about these moths, orange-stripped oakworms, that the onslaught of their masticating caterpillars is late in the season. The harm done to the trees is minimal. Most of the tree’s growth for the season has already taken place before the masses of caterpillars take over.
Here at the museum, I start seeing the adult moths in late May to late June. I begin seeing tiny frass on hard surfaces beneath the trees the moths have laid eggs on in mid to late July. The caterpillars become quite noticeable due to their size, the volume of their frass, and the missing leaves in the trees by the end of July and the first few weeks in August.
It’s also around this time, the first few weeks in August, that we start seeing the caterpillars hiking across the path seeking a place in the nearby woods to pupate. They pupate underground and will emerge about nine moths later as adult moths in late May to late June, when the whole process begins anew.
I will most likely be reminding you of the life cycle of this persistent species of moth around this time next year when I again start seeing the frass collect beneath the trees, the chewed leaves, and the caterpillars hiking across the path on their way to pupate.