IDENTIFICATION AND BEHAVIORAL ASSAYS OF THE TRAIL PHEROMONE OF THE FOREST TENT CATERPILLAR, MALACOSOMA-DISSTRIA HUBNER (LEPIDOPTERA, LASIOCAMPIDAE)

Behavioral assays show that the steroid 5beta-cholestan-3-one, isolated from the abdomen of the larva of the forest tent caterpillar (Malacosoma disstria), constitutes the chemical basis of trail following in this insect. Caterpillars follow artificial trails prepared from solvent dilutions of the compound at rates as low as 10(-11) g . mm -1 of trail, though the true threshold sensitivity is likely to be one or two orders of magnitude lower than this. Fourth-instar caterpillars store an average of 58 ng of the pheromone. Field and laboratory studies indicate that the compound is fully competitive with their authentic trails. The caterpillars are highly sensitive to differences in the concentration of the pheromone, preferring stronger trails to weaker trails. The caterpillars also respond to 5beta-cholestane-3,24-dione, a chemical not found in M. disstria but known to be a component of the trail pheromone of the eastern tent caterpillar, Malacosoma americanum.