The relationship between the structure of nineteen 2,2-dimethylchromene derivatives and their effects on aphid morphogenesis were investigated in a pink clone of the pea aphid, Acyrthosiphon pisurn (Harris). Three bioassay systems were used: (1) wing induction-the induction of winged (alate) progeny by winged adults that normally produce only wingless (apterous) daughters, (2) wing inhibition-the inhibition of production of winged progeny by wingless adults that had been crowd-induced to promote the appearance of winged progeny, ( 3 ) the effect on metamorphosis-the production of precocious adults indicating a decrease in juvenile hormone titre or the induction of supernumerary moults indicating a juvenile hormone agonist effect. Compounds demonstrating wing-promoting effects had short (52 carbon) side chains at the C6 and/or C7 positions while methylation of C5 tended to decrease this activity. Of the seven compounds inducing wing formation, three also inhibited the production of winged progeny. However, the compounds affecting metamorphosis, in particular promoting precocious adult development, were similar to those that promoted wing inhibition rather than those with wing inducing effects; they had alkoxy groups at C7 with lengths of 22 carbons.There is a stronger correlation between compounds interfering with metamorphosis (and therefore evidenced to be affecting juvenile hormone levels, a classic property of some 2,2-dimethylchromene derivatives) and the promotion of wingless forms than the induction of winged forms. This finding is in contradiction to the idea that juvenile hormones are involved i n promoting wingless forms. In addition, attempts to reduce the wing-inducing properties of Precocene were inconclusive and attempts to inhibit wing formation with these two compounds atter crowding were also unsuccessful. The precise mode of action of the 2,2-dimethylchromenes in relation to aphid wing induction remains unclear but it seems likely that the effect is not related to changes in juvenile hormone titres. o 1095 WiIey-Liss, Inc.

A novel concept applying baculovirus-mediated gene silencing to study insect gene function and regulation is described in this paper. A recombinant baculovirus, Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV), was constructed with the juvenile hormone esterase (JHE) gene from the tobacco budworm Heliothis virescens in the antisense orientation, driven by the viral p10 promoter. Infection with this recombinant greatly reduced the haemolymph JHE level and resulted in aberrant morphogenesis of final-instar H. virescens larvae. The body organization remained larval, although the cuticle became hard and brown, similar to pupal cuticle. These results demonstrated that baculovirus-mediated gene silencing can be accomplished and utilized to dissect insect development and to design a new class of baculovirus insecticides.

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. ZUSAMMENFASSUNG Induktion verfrühter Metamorphose und gehemmter Häutung durch FMev, eine Verbindung mit Anti‐Juvenilhormon‐ Wirkung beim amerikanischen weissen Bärenspinner, Hyphantria cunea

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