HORMONE TRIGGER IN INSECTS. “Programmed cell death in larval tissues appears to be transcriptionally regulated in response to ecdysone levels. In both the larval midgut and the larval salivary gland, ecdysone pulses are followed promptly by the expression of the cell-death genes rpr and hid and the subsequent destruction of these tissues.”
http://onlinelibrary.wiley.com/doi/10.1002/(SICI)1097-0177(200005)218:1%3C68::AID-DVDY6%3E3.0.CO;2-9/full