Orgyia pseudotsugata (Lymantriidae)

the Douglas-fir tussock moth


Orgyia pseudotsugata, the Douglas-fir tussock moth, adult male moth; note the pectinate antennae. Male is greyish with feathery antennae, hindwings brown,forewings grey.
Orgyia pseudotsugata, the Douglas-fir tussock moth, adult female moth; note that she is flightless. Female in contrast, has tiny rudimentary wings (therefore flightless) and small thread-like antennae.


Orgyia pseudotsugata, the Douglas-fir tussock moth, larva (caterpillar). Colourful; 2 - 2.6 cm long; densely covered with long hairs, 2 "pencils" of long black hairs project forward from the prothorax, and 1 "pencil" of black hairs projects backwards from the 8th segment of the abdomen. Also note short tufts of coloured hairs on mid-back of first 4 abdominal segments.


Damage: Orgyia pseudotsugata larvae have defoliated the crown, and produced much loose webbing. Eggs are laid on empty cocoons on foliated twigs on the lower half of the tree. Newly hatched larvae feed on new foliage and cause it to shrivel and turn brown. Later larvae feed on both new and old foliage. By late summer, crowns of most of the firs may be completely defoliated. Caterpillars produce loose webbing as they travel from branch to branch which forms a netting which catches and holds pieces of needles dropped as the larvae feed. Severely defoliated trees may be weakened enough to become susceptible to Douglas-fir beetle attack.

Principal Hosts:

Douglas-fir and true firs. In B.C. it feeds primarily on Douglas-fir.

Economic Importance:

Outbreaks periodically develop explosively and after about 3 years subside abruptly due to a nucleopolyhedrosis virus. During outbreaks severe economic damage may occur.

References and Links:

EAG: 483-485; FC: 224.

See HForest and JP17.

Additional Images:

male pupa in cocoon newly hatched female by cocoon damage caused by Douglas-fir tussock moth