Impact of host tree on forest tent caterpillar performance and offspring overwintering mortality

One of the most damaging insect pests in deciduous forests of North America is the forest tent caterpillar, Malacosoma disstria Hübner. It can feed on a variety of plants, but trembling aspen (Populus tremuloides Michaux) is its preferred host and sugar maple (Acer saccharum Marshall) serves as a secondary one in the northern part of its distribution. Because host plant characteristics influence insect performance and survival, we evaluated the impact of trembling aspen and sugar maple foliage on M. disstria performance. Host effects on insect cold hardiness and overwintering survival of offspring were also studied. Forest tent caterpillar reared on aspen leaves had a shorter development time, higher pupal weights and fecundity, and superior egg parameters (length and weight) compared with those reared on sugar maple leaves. Larvae from the two food treatments had low glucose levels during diapause, whereas glycerol content of insects reared on maple was significantly higher during diapause than larvae fed on aspen. Lower glycerol content may explain the higher overwinter mortality of pharate larvae from aspen-reared parents even though their supercooling points were as low as -36 degrees C. This study shows the influence of host plant on insect life history and the need to consider overwintering success and offspring performance in studies to understand and predict population growth and cycling.