Detailed expression profile of bmo-let-7 during B.mori pupa metamorphosis. (A). Profiling during female pupa metamorphosis under artificial culture conditions. (B). Profiling during male pupa metamorphosis under natural culture conditions. The two groups were incubated under different conditions, group A under 25°C and 85%RH, group B under 18–30°C and 40–100%RH. Spinning stage, as well as adult stage, was simultaneously tested in favor of comparative analysis. Two or three days after mounting, cocoon spinning is finished and the larva becomes prepupa. In the following two or three days, the prepupa becomes pupa after molting. The pupa takes 8~11 days to transform into a moth which is white-grey colored. Under natural conditions(18~30°C), the pupa metamorphosis will take 10~11 days; Under man-made conditions (25°C), however, pupa lasts 8~9 days ended as adult moth. U6 and 5srRNA were used as loading controls. 5srRNA and U6 were used as the loading controls and levels of bmo-let-7 RNA are quantified relative to U6.