Dispersal tendencies of neonate larvae of Lymantria mathura and the Asian form of Lymantria dispar (Lepidoptera : Lymantriidae)

Recently, Asian gypsy moth, Lymantria dispar (L.), infestations have been f ound in Oregon, Washington, and British Colombia In at least 1 case, circum stantial evidence suggests that the introduction occurred through airborne dispersal of neonates from grain ships that had been infested in the Far Ea stern ports of Russia. Egg masses of Asian gypsy moth and another lymantrii d, Lymantria mathura Moore, have been intercepted on the same ships. Both s pecies are polyphagous defoliators of trees and could easily achieve pest s tatus if established in North America Neonate larvae of both species are ca pable of airborne dispersal, although there is no information on dispersal rates, or, for L. mathura, on settling velocities. We studied dispersal rat es, settling velocities and diel periodicity of dispersal for both lymantri ids, so this information could be incorporated into models that predict pro bable extent of neonate dispersal. Dispersal rates for L. mathura exceed th ose of Asian and North American gypsy moths. Neonates of L. mathura weigh l ess and have a slower settling velocity than Asian or North American gypsy moths, which allows them to be dispersed by wind for greater distances.