Histological and SEM observations on the invasion and succeeding growth of entomogenous nematode, Steinernema feltiae (str. DD-136), in Spodoptera litura (Lepidoptera: Noctuidae) larvae

Inoculation experiments and histological/SEM observations revealed the invasion and succeeding growth of Steinernema feltiae (DD-136) in Spodoptera litura larvae. At an early time (3 hr) after inoculation, the infective juveniles were not always observed on the mouth or anus of a still active insect. Nematode invasion occurred as promptly as in 1 hr after inoculation with ca. 1, 000 juveniles and then increased with time. Twelve to 24 hr after inoculation, more nematodes were observed in hemocoel than in alimentary canal, especially in the hemocoel lying beneath the deeply invaginated intersegmental membranes. Generally, the most develped nematodes were in the insect head. Nematodes grew rapidly from 24 to 36 hr after inoculation, accompanied by the drastic disintegration of insect tissues in which they often embedded tehmselves. SEM observations clearly revealed a nematode living on and in a larva and also a nematode feeding on rather large pieces of various insect tissues.