Juvenile hormone (JH) plays an essential role during insect development, yet its molecular action is still poorly understood. In Drosophila melanogaster, topical application of JH on white puparium causes it to deposit a second pupal cuticle and prevents the outgrowth of bristles in the abdomen. We previously discovered that gene broad mediates these JH effects. We recently found three P element insertion mutants who were able to develop relatively normal adult abdomen after receiving exogenous JH. The mutations apparently affected a gene on the upstream of broad within JH--pupal cuticle pathway. All these P insertions were located between two genes. We are in the process of determining the gene altered by those P insertions.