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Abstract BackgroundThe blowflyLucilia cuprinais a destructive parasite of sheep that causes flystrike or myiasis. Larvae consume the animal’s living flesh, producing large wounds that can lead to death. The main aim of this study was to identify genes that may play important roles in the behavior and physiology ofL. cuprinalarvae. MethodsAn RNA-Seq analysis of RNA from whole larvae at different developmental stages and third-instar head and gut tissues was used to identify sensory receptors and other genes relevant to the physiology ofL. cuprinalarvae. In addition, CRISPR/Cas9 gene editing was used to obtain a loss-of-function mutation for theL. cuprinaodorant coreceptor gene (LcupOrco). The response of mutant larvae and adult females to fresh and rotten meat at different temperatures was evaluated. ResultsThe RNA-Seq analysis suggested that odorant (OR), gustatory, ionotropic, andPickpocketreceptors may not play a central role in theL. cuprinalarval sensory signaling and digestive systems. Rather, ATP-binding cassettes (ABCs) were highly enriched in head and gut RNA, and odorant-binding proteins (OBPs) only in the head. To confirm that ORs are not essential for larval detection of rotten beef, diet-choice assays were performed including larvae and adults homozygous for a null mutation inLcupOrco. While the attraction of adult females to rotten beef was disrupted,LcupOrcomutant larvae showed no change in diet preference. ConclusionsThe expression pattern of the ABC and OBP gene families suggests a central role in the sensory system of theL. cuprinalarva for these receptors. Behavioral assays showed that ORs are essential for the adult female response to rotten beef, but not for larval behavior. These findings are consistent with high levels of expression ofLcupOrcoin the adult female antenna but very low expression in larvae. Graphical abstract