Temperature profiles inside webs of the fall webworm, Hyphantria cunea (Lepidoptera: Arctiidae): Influence of weather, compass orientation, and time of day

1. Webs of the fall webworm ( Hyphantria cunea) were studied to determine how web temperatures change over 24-h periods. 2. Temperatures inside webs were strongly elevated compared to ambient temperatures for 6–8 h per day. On rainy, overcast days and at night, however, web temperatures were very close to ambient temperatures. 3. South-facing and north-facing webs were not significantly different in their capacity to absorb and retain heat. Directions of webs were not biased toward south, north, east, or west. 4. Although webworms cannot physiologically elevate body temperatures, they clearly do create living spaces that efficiently capture diurnal environmental heat.