EXPERIMENTAL MANIPULATION OF THE PHENOLOGY OF EGG HATCH IN CYCLIC POPULATIONS OF TENT CATERPILLARS

Eggs of western tent caterpillars hatch just as leaves of their food plants are developing. To determine the impact of asynchrony between leaf development and egg hatch during a year of peak density and the initiation of decline, egg masses were introduced to four study areas after the time of normal egg hatching. Survival of caterpillars was not significantly influenced by delays of 3-6 weeks in hatching. Populations composed primarily of introduced insects and control populations declined following the summer of the experiment. Although hatching of deployed eggs was delayed, caterpillar development during warmer temperatures later in the spring was sufficiently rapid that caterpillars from all groups reached the fifth instar by mid-June, and parasitization of caterpillars from control and experimental areas was similar. Tent caterpillar survival was apparently resilient to substantial delays in egg hatch which suggests that cyclic population declines are not likely to be associated with minor variation in the synchrony of leaf development and egg hatch.