Critical period for pupal commitment in the yellow fever mosquito, Aedes aegypti.

Changes in ecdysteroid levels that lead to commitment of pupal and adult development were studied in the yellow fever mosquito, Aedes aegypti. Application of juvenile hormone at the time of pupal commitment usually results in delay or blockage of pupal and adult development. With methoprene, a juvenile hormone mimic, the JH sensitive period was found to be within 19 h after ecdysis to the fourth instar, at which time methoprene treatment caused a delay in pupation. Consistent with this observation, there was a small peak of ecdysteroid levels between 14 and 28 h after ecdysis to the fourth instar. Therefore, the commitment to pupal development occurs most likely between 14 and 19 h after ecdysis to the fourth instar. Levels of transcription of the ecdysone receptor gene show a small peak between 12 and 24 h, and a larger peak between 46 and 66 h after ecdysis to the fourth instar.