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Excerpts from Jim Conrad's
Naturalist Newsletter
from the April 6, 2009 Newsletter, issued from the forest near Natchez, Mississippi; elevation ~400ft (120m), ~N31.47°, ~W91.29°:
ROVING TENT CATERPILLARS
This week I've run across several two-inch long Eastern Tent Caterpillars, MALACOSOMA AMERICANUM, one of which you can see atop my hand above.
To figure out why these lone, wandering, as-large-as-they-get caterpillars are suddenly turning up I reviewed the tent-caterpillar life cycle. Here it is:
The adult moth lays her eggs in late spring or early summer. The eggs hatch the following spring, just as tree buds begin expanding. Newly hatched caterpillars immediately start building a silken tent in a tree, expanding it each day. The caterpillars feed three times daily -- just before dawn, at mid-afternoon, and in the evening after sunset. When they leave their tent they add silk to it, move to nearby leaf-grazing limbs en masse, feed, then return to the tent where they rest until the next feeding period. Right before metamorphosing they begin feeding only at night. When they're ready to metamorphose they wander off and build cocoons in protected places. Adult moths, which are nocturnal, emerge about two weeks later, mate and the females lay eggs the same day they emerge from their cocoons. The females die soon thereafter.
So, wandering Eastern Tent Caterpillars encountered nowadays already have built their tents and eaten and grown, and now are looking for protected spots in which to construct cocoons where they can metamorphose. A tent hangs inside a mostly defoliated Black Cherry tree near my trailer, and you can see it below:
That tent, about the size of a basketball, full of caterpillar feces and dead caterpillars, is abandoned, having served its purpose by spawning at last some of the wandering caterpillars I'm seeing these days.
Wikipedia provides an especially informative page at https://en.wikipedia.org/wiki/Eastern_tent_caterpillar.