Effects of pyriproxyfen, a juvenile hormone analog, on development of the mealworm, Tenebrio molitor

Pyriproxyfen, an analog of the juvenile hormone (JH) in insects, has been evaluated in vivo and in vitro on an important stored product pest, the mealworm Tenebrio molitor. On newly ecdysed pupae, this insect growth regulator (IGR) was applied topically (at 0.10 and 0.20 μg/insect). Enzyme immunoassay measurements showed a decrease of the ecdysteroid titer in the hemolymph of treated specimens. In addition, the treatment induced an increase of the protein concentration in the hemolymph, however, there was no significant effect on the protein band pattern. Using in vitro pupal integument explant cultures, pyriproxyfen (at 1 and 10 μM in the medium) caused a significant inhibition of ecdysteroid amounts and of the thickness of new cuticle secreted. These new results are discussed in relation to the physiology of this IGR with a JH action.