Abstract
Experiments were carried out to compare the changes of the ecdysteroid titers during the 3rd and 4th instars in the haemolymph of various trimolting larvae i. e. dominant trimolting larvae, recessive trimolting larvae, trimolting larvae segregated from dimolting larvae and trimolting larvae induced by high temperature and moisture treatment applid to tetramolting larvae. A small incrcose in the ecdysteroid titers in the haemolymph of recessive trimolting larvae and trimolting larvae segregated from dimolting ones was abserved during the early stage of the 4th instar, but the pattern of changes of the ecdysteroid titers is the dominant trimolting larvae during the 4th instar was diefferent from those in the recessive trimolting larvae. This phenomenon ascribed of the differences in the secretory activity of the prothoracic glands of the two types of trimolting larvae before they entered the 3rd ecdysis. The ecdysteroid titers in the haemolymph of the trimolting larvae induced by the high temperature and moisture treatment applied to the tetramolting laryae during the first four days of the 4th instar were very low, It is thus considered that the inhibitory effect of the high temperature and moisture treatment applies to tetramoling largae during the early stage of the 4th instar on the ecdysteroid level may play an important role in the induction of trimolting larvae.
