Susan Ellis, Bugwood.org
Most homeowners will not notice young gypsy moth larvae as they are less than 1 cm long, nondescript, spend most of their time in the tree canopy, and consume relatively little foliage. Early instars are dark in color with orange splotches on the back.
Older larvae have distinguishing pairs of blue and red tubercles along their backs and striking dark markings on the head that resemble vertical eyespots.
Pupae are somewhat teardrop shaped, and female pupae are noticeably larger than male pupae.
Pennsylvania Department of Conservation and Natural Resources - Forestry Archive, Bugwood.org
Michigan State University, Bugwood.org
female (top) and male (botttom) pupae
Milan Zubrik, Forest Research Institute
Slovakia, Slovak Republic, Bugwood.org
pupae, skins, egg masses in tree crevice
The image to the above left is common in high populations where pupae, cast skins from larval molts, and newly laid egg masses are found collectively in cracks and crevices of trees.
Adult males are light brown with wavy black markings on the wings and have feathery antennae. Females are white with brown markings and have non-feathery antennae. Males are strong but erratic flyers whereas females do not fly.
female laying egg mass
State Phytosanitary Administration, Bugwood.org
USDA APHIS PPQ Archive, Bugwood.org
For more information:
Fairfax County has a good description of insects often confused with gypsy moth.
The Ohio Department of Agriculture has a very good series of photos and descriptions for all gypsy moth life stages.