White-Marked Tussock Moth

Orgyia leucostigma — the white-marked tussock moth — is one of the most spectacularly-colored caterpillars in temperate North America and a significant defoliator of broadleaf trees. Mature caterpillars are 3-4 cm long, bright yellow with a vivid red head capsule and reddish dorsal stripes, four conspicuous white 'tussock' tufts of long bristles on the dorsal abdomen, and two long black 'horn' tufts projecting forward over the head. The bristles are urticating (defensive setae): contact with skin causes immediate painful welts in most people, and in sensitive individuals can produce severe allergic dermatitis lasting days. Caterpillars feed on a wide range of broadleaf trees including oak, willow, birch, maple, apple, and cherry; populations periodically outbreak and defoliate large patches of forest, parks, and orchards across the eastern and central US and Canada. The adult moth is dramatically sexually dimorphic: males are 25-35 mm wingspan, gray-and-brown with feathered antennae, and capable fliers; females are FLIGHTLESS — they emerge from the cocoon as wingless gray-white grubs, release pheromone, mate with arriving males, lay 200-300 eggs ON THE COCOON ITSELF, and die. Females never feed and never leave the cocoon site. The eggs overwinter and hatch the following spring. Several closely related Orgyia species (the Douglas-fir tussock moth O. pseudotsugata and the rusty tussock moth O. antiqua) are similarly cryptic-female and similarly significant tree defoliators.