Here’s the culprit, the eastern tent caterpillar.
Known scientifically as Malacosoma americium, this caterpillar leads a surprisingly well-ordered life.
These bugs are the spawn of a moth. Late one spring she lays 200 to 300 eggs in a tree from the Rosaceae family — in Florida, that means peach trees.
The eggs hatch and the baby caterpillars wait patiently until the following spring, when they emerge to build a tent made of silk. Three times each day they troop out of the nest to feed on other parts of the tree, then return to the nest afterward to rest. And each day they add silk to the best, constructing layer after layer of space where they can rest between meals.
It’d be bad enough if these Bad Bugs only fouled and defoliated peach trees. However, they’ve been implicated in another, more serious phenomenon.
Veterinarians suspect that pregnant mares can miscarry after consuming eastern tent caterpillars. In Kentucky in 2001 between 20 percent and 30 percent of the state’s pregnant mares miscarried, and an exhaustive investigation showed that eastern tent caterpillars were present at the places the mares had lived.
Scientists still aren’t sure what effect the caterpillars might have, but they advise horse owners not to take chances.