Adult forest tent caterpillars have a wingspread of 1-1 1/2 inches (2.5-3.8 cm) and are stout-bodied and pale yellow to yellow-brown. Two darker oblique lines go along the centre of the forewings.
Cemented eggs are covered with a frothy, glue-like material that solidifies and turns a lustrous dark brown. Larvae are virtually uniformly black, approximately 1/8 inch (3 mm) long, and strikingly hairy when they hatch.
The specific patterns of adult larvae grow increasingly visible with each succeeding molt—pale blue lines along the sides of a brownish body with a mid-dorsal row of the keyhole- or footprint-shaped, white dots on a black background.
Caterpillars grow around 2 inches (50 mm) in length when fully developed. Cocoons are thick, yellowish silk with powdered particles intertwined between the strands.
Host plants:
Hosts include many hardwood tree species, and preference varies by location. Although alder, basswood, birch, cherry, cottonwood, elm, oak, poplar, different fruit trees, and willow are all good hosts in the western United States, aspen is the favored host. Atypical hosts, such as understory shrubs and fruit and vegetable plant leaves, may be consumed by hungry, roving larvae if trees are yellowing leaves.
Territory:
North American epidemics have covered thousands of square kilometers and lasted years. Defoliation causes more than 70% growth loss and minimal tree mortality. Defoliation can kill gum trees in southern bottomlands. When the leaves fall off sugar maples in the northeastern US, the amount and quality of maple syrup go down.
Damages caused by Forest Tent Caterpillar:
Forest tent caterpillars don’t damage deciduous trees since they may grow new leaves in the same season. Healthy trees can withstand two to three years of intense defoliation after four years of heavy defoliation and drought-stressed trees.
Life history and habitat:
The woodland tent caterpillar breeds once a year. Early spring sees egg mass larvae emerge along with host tree buds. Egg hatching peaks in Florida around March, but it can occur as early as mid-February or as late as April. Young larvae eat buds, leaves, and flowers together. Forest tent caterpillars eat leaves after five larval instars. Late instar larvae roam host trees in search of food or a location to pupate. Caterpillars and their droppings cause problems for people throughout the two to six weeks they are visible, especially as they mature. The pale-yellow pupal cocoons are found on webbed leaves, bark cracks, shrubs, and building sides and overhangs. After 10–14 days, adult moths emerge, mate, and lay egg masses on host trees. Adult moths don’t eat and survive just two to 10 days, although they can cause problems when they gather around evening illumination. Adults have emerged as early as February in Florida (J.B. Heppner, personal communication). Pharate larvae form in egg masses by autumn and hibernate through winter before resuming the cycle in spring.
