Ranking of the housekeeping genes in adult desert locust brain tissue. Gene expression stability of the housekeeping genes by (A) geNorm and (B) Normfinder in adult desert locust brain tissue. (A) geNorm gives an average expression stability measure (AESM) as the mean of the stability values of the remaining genes in a stepwise exclusion process. The lower the AESM, the more stable the gene in the subset. The threshold for an unstable gene is M ≥ 1. 5 (B) Normfinder calculates a stability value which is also inversely proportional to the stability of the gene under study.