Abstract: The symptoms and histopathological changes in the midguts of Anomala corpulenta and A. exoleta larvae infected by Bacillus thuringiensis HBF-1 strain were observed using histopathological slice. The results showed that no obvious symptom of the larvae was observed at the beginning of HBF-1 infection. With the time increasing, the infected insect appeared inactive, paralyzed and lost its sensitivity to the environment, and finally became blackish, straight or shrinked until to death. The results of histopathological obeservations under microscope showed that the midgut cells appeared with malformation and vacuolization 3 days after HBF-1 infection, and were seriously damaged and even destroyed completely 7 days after infection, while the epithelium began to deviate from the membrane 10 days after infection. In the newly dead insects, the epithelium shed completely together with the endocyte.

Key words: Anomala corpulenta, Anomala exoleta, Bacillus thuringiensis, midgut, histopathology