16S rRNA sequencing: mid gut
According to the manufacturers instructions, total genomic DNA was extracted from the midgut of one BSFL individual using the TGuide S96 Magnetic Soil /Stool DNA Kit (DP812, TIANGEN) (21 replicates were set for each clade). The V3-V4 region of the bacterial 16S rDNA gene was amplified using the primers 338F (5'- ACTCCTACGGGAGGCAGCA-3') and 806R (5'- GGACTACHVGGGTWTCTAAT-3'). Then the size and quantity of the amplicon library were assessed on a Qsep-400 (BiOptic, Taiwan, China), and the qualified libraries were sequenced on the Novaseq 6000 platform (PE 250).