Tree Insects - Forest Tent Caterpillars

The forest tent caterpillar is broadly distributed throughout North America. As with all tent caterpillars, there is just one generation each year. This caterpillar will not make a tent.  They feed in such large numbers it resembles a tent over the leaves.
Note square ends to egg casing, egg can be seen with naked eye on twigs prior to Spring hatch
The egg mass with its enclosed quiescent caterpillars is the overwintering stage. Eggs hatch and the first of the active larval instars appears in the early spring just as the buds of the host tree are begining to expand. The caterpillars grow rapidly and after feeding for about 2 months, spin cocoons and pupate. About 3 weeks later the adults appear and shortly thereafter the moths lay their eggs and die.
forest tent caterpillar
This Caterpillar is often confused with Gypsy Moth.  Note the white spots across the top.  This caterpillar is generally not a problem but can be controlled with contact insecticide applications.
Forest Tents can defoliate in out break populations.  Forest Tent out breaks are more numerous than Eastern Tent but not as often as Gypsy Moth.  2006 and 2007 was the last time this insect was in out break populations.
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