Abstract: 【Aim】 To clarify the change in the bacterial community in larval midguts of the striped stem borer,  Chilo suppressalis  (Lepidoptera: Crambidae) after treatment with Bacillus thuringiensis insecticidal proteins. 【Methods】 Midguts were dissected from C. suppressalis  larvae that were collected from Beijing (BJ) and Fuzhou (FZ) of China and successively reared with artificial diets without Bt insecticidal proteins and with Bt insecticidal proteins (Cry1Ab, Cry1Ac and Cry1Ca), respectively. Degeneration gradient gel electrophoresis (DGGE) and Illumina MiSeq platform were employed to detect the bacterial community in these midguts and to compare its difference among different treatments (BJCK, BJCry1Ab,BJCry1Ac, FZCK and FZ1Ca) of the two populations. 【Results】 The DGGE profiles demonstrated that there was difference in bacterial abundance in larval midguts of C. suppressalis among different treatments. Analyses on DNA sequence of 16S rDNA libraries indicated that among the midgut bacteria  Enterococcus bacteria of Firmicutes was the most dominant, followed by bacteria of Lactobacillus  and Bacillus (Firmicutes), Proteobacteria, Chloroflexi, and Bacteroidetes. The proportions of the dominant Enterococcus bacteria in the larvae treated with Bt insecticidal proteins (BJCry1Ab, BJCry1Ac and FZ1Ca) were higher than those in the larvae without treatment with Bt (BJCK and FZCK), but the proportions of Lactobacillus bacteriawere lower in the larvae treated with Bt insecticidal proteins. The bacterial abundance also differed between BJCK and FZCK. 【Conclusion】 The results suggest that the bacterial abundance in larval midguts of  C. suppressalis  changes after treatment with Bt insecticidal proteins, which may be related to the difference in Bt insecticidal proteins, geographical sites and successive rearing time.

Key words: Chilo suppressalis, midgut, PCR-DGGE, 16S rDNA libraries, bacterial, Bacillus thuringiensis