AERIAL DISPERSAL BEHAVIOR OF LARVAL BAGWORMS, THYRIDOPTERYX EPHEMERAEFORMIS (LEPIDOPTERA: PSYCHIDAE)

Abstract

Seasonal and daily patterns of ballooning, and behavioral processes involved in aerial dispersal of the bagworm, Thyridopteryx ephemeraeformis (Haworth), were studied on Juniperus virginiana L. in Kentucky. The aerial dispersal period began in mid-May 1983 and lasted ca. 1 month. About 75% of dispersing larvae ballooned after making a bag. Settling velocities were determined for larvae with and without bags and trailing varying lengths of silk; a model was then developed that predicts dispersal distance for a particular wind speed and departure height. Most aerial dispersal is probably short-range. The bag reduced potential dispersal distance, but larvae with bags survived ca. 2 days longer than those without bags when exposed to abiotic factors off of a host. Larvae without bags ballooned mostly in morning, whereas 80% of the larvae dispersing with a bag ballooned in the afternoon. These patterns may be related to the diel periodicity of emergence of neonate larvae from old female bags, and the subsequent behavior of 1st instars prior to dispersal. A large proportion of each cohort emigrates regardless of host condition.