During the transition from wandering larvae to pupation, the flesh fly, Sarcophaga crassipalpis, undergoes a complex series of developmental changes driven by pulses of ecdysone. The wandering larvae, undergoes a series of processes where the larval cuticle barrels, or rounds up becoming smooth, hardening and sclerotizing to form the puparial case. In a couple of days at 25oC, the internal pupal cuticle forms and undergoes apolysis, separating from the tanned puparial case. A direct examination of this process is difficult since it takes place behind the opaque puparial case. We have examined the CO2 respiration during this developmental change and have found a complex but reproducible pattern of respiratory cycles during this period. This suggests a novel and unique developmentally complex control of respiration that is different from passive ventilation or discontinuous gas exchange reported in other systems. Partial support was provided by HHMI Symbiosis Grant # 52005872.