A group of small ribonucleic acids (RNAs), known as microRNAs (miRNAs), have been found to play significant roles in the biology of all multicellular organisms, including insects. They are naturally produced in animal and plant cells and control key biological processes such as embryogenesis, differentiation, development, immunity, etc by regulating expression of various genes. Disruptions in miRNA production or activities have been shown to lead to abnormal development and cancer. In this project, we aimed to explore the possibility of disrupting the function of miRNAs in key insect pests, the cotton bollworm Helicoverpa armigera and the diamondback moth Plutella xylostella, by feeding their larvae with artificial inhibitors of a selected group of miRNAs that are highly produced in the insects