Caterpillars may seem like harmless fuzzies, but some of them can snuff out lives. Take the Eastern tent caterpillar, a dark brown, two-inch-long wiggler with a white racing stripe.

Tent caterpillars hatch from egg masses on wild cherry, crabapple and related trees then build webbed nests in trunk forks before eventually falling to the ground. Pregnant mares that inadvertently eat caterpillars while grazing are likely to abort their foals. This Mare Reproductive Loss Syndrome was identified only after Kentucky lost one-third of its spring foals to these callous crawlers in 2002.

Brown egg masses can sometimes be found on tree branches before caterpillars hatch and swarm in the early spring in Florida and late spring to early summer in northern states. Safe pesticides can be used to kill eggs before caterpillars have a chance to wreak havoc.