Insect cuticular lipids are a complex cocktail of highly diverse cuticular hydrocarbons (CHCs), which form a hydrophobic surface coat to maintain water balance and to prevent desiccation and penetration of exogenous substances. Fatty acid elongases (ELOs) are key enzymes that participate in a common CHC synthesis pathway in insects. However, the importance of ELOs for CHC synthesis and function remains understudied. Using transcriptomic data, we have identified seven ELO genes (LmELO1-7) in the migratory locust Locusta migratoria. We determined their tissue-specific and temporal expression profiles in fifth instar nymphs. As we are interested in cuticle barrier formation, we performed RNA interference against LmELO7, which is mainly expressed in the integument. Suppression of LmELO7 significantly decreased its expression and caused lethality during or shortly after molting. CHC quantification by GC-MS analysis indicated that suppression of LmELO7 resulted in a decrease in total CHC amounts. By consequence, CHC deficiency reduced desiccation resistance and enhanced cuticle permeability in LmELO7-suppressed L. migratoria. Interestingly, LmELO7 expression is induced at low air humidity. Our results indicate that LmELO7 plays a vital role in the production of CHCs and, hence, cuticle permeability. Induction of LmELO7 expression in drought conditions suggests a key role of this gene in regulating desiccation resistance. This work is expected to help developing new strategies for insect pest management based on CHC function.