Notch signaling generates the "cut here line" on the cuticle of the puparium in .

During a molt or eclosion, insects shed their cuticle, an extracellular matrix made by underlying epidermal cells, by cleavage along a defined line. This means that the "cut here line" is pre-formed on the cuticle, and its formation is indispensable for insect life. Here, we show that the proper formation of the operculum ridge (OR), which is the "cut here line" on the puparium (pupal case) of , involves Notch signaling activation in the epidermal cells just beneath the future OR region (OR-forming cells). The inhibition of Notch signaling causes defects in eclosion due to failure in OR cleavage, the chitin organization and several cuticular proteins localization, glucose dehydrogenase (Gld) activity, and OR-forming cell shape. Our findings provide the first insight into the molecular basis of the structure and formation of the "cut here line" on the cuticle.