These are tent caterpillars, the larvae of the moth called Malacosoma americanum.
In late April and early May, these caterpillars appear in their little tents in just about every black cherry tree (Prunus serotina), and during certain years, they actually denude the trees of nearly all their leaves.
[…] Tent caterpillars on a black cherry tree […]
The little blighters killed my only cherry tree years ago. Their webs were everywhere, it seemed, that year.
If it’s not a frosty spring, they will destroy all the leaves off of black cherries, edible cherries, and peach and plum trees.