Ranking of the housekeeping genes in desert locust brain tissues of L5 nymphs. Gene expression stability of genes in brain tissue of L5 nymphs using two software programs; (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.