From Matt Ayres, professor of biological sciences at Dartmouth, via Dorothy Heinrichs:
It is an exciting year for caterpillars in our region!
The damaged leaves are from a group of caterpillars (the Notodontidae), which have the habit of clipping the leaf off after they have eaten part of it. Presumably this is to make it harder for birds to find them. Caterpillars are more abundant this year than they have been in at least 20 years in our region. I was at Hubbard Brook Experimental Forest (USFS forest near Woodstock NEW HAMPSHIRE) a few days ago (some photos enclosed). I was part of a team that found many caterpillars while heroically getting a sample for 2020 for our long term data. One could hear a steady rain of insect frass from the canopy. This years is supporting what we have described for caterpillars in and around Hubbard Brook. Total abundance fluctuates by 20-fold or more among years. When caterpillars are abundant it is many different species that are involved. And it is region wide. Thanks to Dorothy’s observation we can add Mt. Cardigan to regional caterpillar map. The last photo in the enclosure shows an amazing photo of a warbler delivering a Notodontid caterpillar to its nest. The birds are very happy! This is not an “epidemic” or anything bad. It is the natural fluctuations of the forest community. The abundant caterpillars this year seems like a good thing to us because we have even begun to wonder if the caterpillars would ever be abundant again.
Hit the link below to see Prof. Ayres' caterpillar photos and explanations.