[Circulating ecdysone levels in late larval stages and the induction of the nymphal diapause in Pieris brassicae].

Ecdysone titers of hemolymph are measured during 5th larval instar of Pieris brassicae reared under either conditions inducing pupal diapause or continuous development. The peak values for the two conditions are not different and, therefore, seem not to be related to the mode of development. A few hours before larval-pupal ecdysis, a new secretory activity begins only in the non diapausing prepupae. Ecdysone injections in diapausing prepupae give results that agree well with those above.