Thermal properties of the tent of early instar colonies of the eastern tent caterpillar, Malacosoma americanum (Lepidoptera: Lasiocampidae)

The extent to which the small tents of the early instars of Malacosoma americanum warmed when irradiated by sunlight was investigated by continuous electronic monitoring of field colonies for 137 colony-days. Tent temperatures exceeded the threshold for larval growth of 15 °C on 88–96% of the study days, exceeding in degree-minutes the ambient excess-over-threshold by a factor of approximately five. In still air, tents constructed by third instar caterpillars achieved greater temperature excesses over ambient than did a model of a tightly sealed glass house, but smaller tents and tents exposed to simulated wind did not perform as well. Tents of M. americanum warmed more rapidly and to a high temperature than silk nests of markedly different design constructed by other species.

► The extent to which tents of early instars of Malacosome americanum warmed when irradiated was monitored for 137 colony-days.
► Tent temperatures exceeded the threshold for larval growth on 88–96% of the study days.
► The fully formed tents of third instar caterpillars performed as well or better than a model of a tightly sealed glass house.
► The tents warmed more rapidly and to a higher temperature than silk nests of other designs.
► Tents devoid of occupants warmed well above ambient temperatures.