Estimation of Predation Rates of Gypsy Moth Larvae by Exposure of Tethered Caterpillars

Abstract

Data were gathered during two years on the death and removal of gypsy moth. Lymantria dispar L.. larvae tethered by threads in various forest microhabitats where gypsy moth densities were low. These data were used to estimate larval mortality rates due to predation, after first correcting for several sources of bias. Values were similar for young and old larvae. but were higher and more variable in the second year. The estimates were used to run Monte Carlo simulations to determine variations in daily predation rates. The average daily predation rate for one of the years, 0.121, was very close to the daily mortality rate found from declines in population estimates between early and late-larval instars obtained from mark-recapture studies. In this low-density gypsy moth population, predation was by far the most important mortality factor.