Effects of a juvenile hormone analogue on the metamorphic changes of the foregut and midgut in Tenebrio molitor L. (Insecta, Coleoptera)

During normal Tenebrio metamorphosis, the smooth pupal foregut cuticle is replaced by a thicker adult cuticle with spines. The pupal midgut epithelium includes regenerative cells organized into nests that proliferate during pupal life, protruding as crypts into the general cavity. At high levels of treatment with juvenoid (Methoprène), some adult characteristics of the foregut cuticle were observed: the foregut cuticle apolysed soon after ecdysis, and the duration of cuticular secretion was shortened. Differentation of the pupal midgut into the adult form was either stopped or delayed by the juvenoid; the growth of the crypts was often inhibited in supernumerary pupae and in other cases could be observed 10 days later than in controls.