Abstract
Histological and scanning electron microscopic observations were made to reveal the infection of Steinernema feltiae in the common cutworm, Spodoptera litura, via routes other than the alimentary canal. The infective juveniles (JIIIs) invaded the larval, pupal and adult spiracles of Galleria mellonella, while they did not invade the S. litura spiracles of the last instar larva or pupa aged 3 days after pupation. Many JIIIs congregated in the vesicle under the esophagous of the S. litura larva and some JIIIs penetrated the thin cuticular membrane of the vesicle. The nematodes also penetrated wounded tissues on the insect integument. A few JIIIs were assumed to infect the larva through its thin intersegmental membrane, but no direct evidence was obtained. The firm framework of the JIIIs head may be responsible for the mechanical invasion through the cuticular membrane.
