The slug caterpillar Parasa lepida (Lepidoptera: Limacodidae) is an introduced pest to urban trees in western Japan. The spatial distribution pattern of P. lepida cocoons was examined on cherry trees along an urban coastal avenue with reference to the effects of distance from the sea, dieback of trees, and avian predation. Stepwise multiple regression analysis revealed that cocoon density increased and tree dieback decreased with distance from the sea. These results suggest that salt spray from the sea and the resulting plant stress may negatively affect the moth. Avian predation rate increased with cocoon density per tree, suggesting density-dependent predation. Also, the predation rate was higher on cocoons between 0.5 and 1.5 m above ground, where the twigs were cleared and prop wood was fixed. These spatial distribution patterns are discussed with regard to pest control.