PRECOCIOUS METAMORPHOSIS AND MOULTING DEFICIENCIES INDUCED BY AN ANTI‐JH COMPOUND, FMEV IN THE FALL WEBWORM, HYPHANTRIA CUNEA

Abstract

Fluoromevalonate (FMev, ZR‐3516) known as an inhibitor of JH biosynthesis was topically applied in 0.1 to 50 μg/specimen doses to the 3rd, 4th, and 5th instar caterpillars of Hyphantria cunea Drury. The anti‐JH compound induced 3 main types of specific responses: 1) precocious metamorphosis, 2) inhibition of ecdysis, and 3) prolongation of larval development. Precocious pupation was accompanied by behavioural events typical of normal pupation. Third and 4th instar larvae metamorphosed prematurely mostly with the intervention of an intercalary larval instar. The 5th instar exhibited the highest sensitivity to the anti‐JH agent. Within each larval stage the freshly moulted insects proved to be the most susceptible to FMev. Afterwards, the incidence of morphogenetic reaction gradually decreased with age. In another fraction of Hyphantria larvae not responding with precocious pupation, FMev evoked varying degrees of ecdysial disturbance which always resulted in the death of caterpillars. In most cases the anti‐JH compound inhibited the premature pupal moult, too, and these affected insects died as tanned pharate pupae. A complete or partial “rescue” from the effects of FMev was elicited, if simultaneously or subsequently, a single topical dose of a JH analogue, hydroprene was also administered.M. R. Abo‐Elgar, Monoufia Univ., Shibin El‐Kom, Egypt, on occasion of his 60th birthday.ZUSAMMENFASSUNGInduktion verfrühter Metamorphose und gehemmter Häutung durch FMev, eine Verbindung mit Anti‐Juvenilhormon‐ Wirkung beim amerikanischen weissen Bärenspinner, Hyphantria cunea