PRECOCENE DERIVATIVES AND APHID MORPHOGENESIS

The precocenes have notable effects on insect development, in particul ar they can induce specific destruction of corpora allatal cells and t hus prevent the synthesis of juvenile hormones. As juvenile hormones h ave wide-ranging physiological roles in insects, from metamorphosis to reproduction, the effects of precocenes are also diverse. It has been suggested that high juvenile hormone titres in aphids induce the deve lopment of wingless adult forms while low titres promote the developme nt of winged forms. The morphogenetic effects of precocene derivatives on aphids are complex. They can affect wing dimorphism in some specie s, both promoting wing development and inhibiting wing development, de pending upon experimental strategy, and can exhibit the classical indu ction of precocious adult development indicating destruction of the co rpus allatum. The morphogenetic effects promoted by a series of precoc enes and 2,2-dimethylchromene derivatives have been investigated in th e pea aphid, Acyrthosiphon pisum (Harris), and structure-activity rela tions determined for wing induction, wing inhibition, and precocious m etamorphosis. These experiments show that compounds which promote wing development are not, or not so, effective in wing inhibition and that the compounds that inhibit wing formation are more closely aligned wi th those that induce precocious metamorphosis. Substitution of alkylth io for alkoxy groups at C7 alters the morphogenetic activity profile w hile 2,2-dimethylchroman derivatives have no morphogenetic activity. ( C) 1996 Wiley-Liss, Inc.