PRENATAL AND POSTNATAL EFFECTS OF PRECOCENES ON APHID MORPHOGENESIS AND DIFFERENTIAL RESCUE

Post-natal application of Precocene II (6,7-dimethoxy-2,2-dimethylchro mene, PII) to newly-born pea aphid larvae, Acyrthosiphon pisum (Harris ), does not influence development and the PII promotion of winged prog eny previously reported after pre-natal application appears to be exer ted via a maternal control mechanism. The production of winged progeny by crowded, wingless adults can be inhibited by both pre- and post-na tal application of Precocene III (6-methoxy, 7-ethoxy-2,2-dimethylchro mene, PIII). Precocene III treatment also induces precocious adult dev elopment, i.e., early metamorphosis. Both wing inhibition and precocio us metamorphosis were dose- and age-dependent when pill was post-natal ly applied. Pre-natal application of juvenile hormone III or its agoni st, pyriproxyfen, following treatment with PII or PIII, did not influe nce the precocene effects on wing induction or inhibition, respectivel y. Post-natal treatment with the juvenile hormone and pyriproxyfen, su bsequent to PIII, reversed the precocious metamorphosis effect but not wing inhibition. This differential result, with an identical rescue p rotocol, suggests that PIII induction of precocious adult development arises as the result of the selective destruction of the corpus allatu m cells and a lowered JH titre. However, the property of PIII that pro motes the development of wingless forms appears unrelated to this decr ease in juvenile hormone titre. (C) 1996 Wiley-Liss, Inc.