Stability of candidate reference genes in different tissues of male (A) and female flies (B), and optimal number of reference genes for normalization (C) in Bactrocera dorsalis evaluated by geNorm. geNorm proceeds with stepwise exclusion of genes with relatively higher variable expression among the samples. The expression stability measure (M) is the average of the stability values of the remaining genes. The lower the M value, the more stable the gene in the subset. Bar values indicate the magnitude of the change in normalization factor after the inclusion of an additional reference gene. A large variation indicates that the added gene has a significant effect and should probably be included for calculation of the normalization factor. Same as in Figure 2.