The distribution of larval colonies of the Silver Spotted Tiger Moth (Lophocampa argentata Packard) (Lepidoptera: Arctiidae) was documented in the canopy of a 2.3 ha patch of Douglas-fir/Western Hemlock forest using a 75 meter tall tower crane, in the central Cascade mountains, Washington State, USA. The Silver Spotted Tiger Moth overwinters as larval colonies in tree canopies. Colonies were surveyed 4 December 1995, and 19 December 1996. In 1996 no colonies were present. For each colony, tree species, crown class, crown position and aspect from tree crown were noted. In 1995, 68 colonies were observed on 32 individual codominant trees in the 2.3 ha research area under the jib of the canopy crane. Ten colonies (14.7%) were on Western Hemlock, while 58 (85.3%) were on Douglas-fir, apparently reflecting a preference for Douglas-fir. The colonies were predominantly in the upper crown (> 40 m) areas (87.9%), with some colonies in the mid crown (20-40 m) area (10.3%), and no colonies in the lower crowns (0-20 m). The primary aspects included south (54.4%), southeast (14.7%), and southwest (13.2%), with the apex (5.8%), east (10.3%) and west (1.5%) aspects accounting for all the remaining colonies. No colonies were located on the north, northeast or northwest aspects. These observations suggest that selection of larval colony sites reflects adaptation to exploiting the sunny portion of the tree crown and the portion of the forest which is warmest on sunny days, and this facilitates thermoregulation and winter activity. Additional attributes of thermoregulation in this species are: larvae are dark colored and hairy, build tents, bask in the sun, and aggregate for basking.
