Significance The RNA interference (RNAi) discovered in nematodes has contributed to major advances in basic and applied sciences. RNAi-based methods are being developed for controlling pests and disease vectors. RNAi is highly efficient and systemic in coleopteran insects, but not in other insects. The lower efficiency of RNAi in economically important insects and concerns about resistance development are hindering the widespread use of this technology. To address these problems, a RNAi-sensitive Colorado potato beetle, Leptinotarsa decemlineata , and a cell line derived from this insect were used to identify a dsRNA-binding protein, StaufenC , as a major contributor to RNAi and its resistance. Interestingly, StaufenC homologs are present in only coleopteran insects and are essential for efficient RNAi response and its resistance in these insects.