Pre- and post-natal effects of precocenes on aphid morphogenesis and differential rescue

Post-natal application of Precocene II (6,7-dimethoxy-2,2-dimethylchromene, PII) to newly-born pea aphid larvae, Acyrthosiphon pisum (Harris), does not influence development and the PII promotion of winged progeny previously reported after pre-natal application appears to be exerted via a maternal control mechanism. The production of winged progeny by crowded, wingless adults can be inhibited by both pre- and post-natal application of Precocene III (6-methoxy, 7-ethoxy-2,2-dimethylchromene, PIII). Precocene III treatment also induces precocious adult development, i.e., early metamorphosis. Both wing inhibition and precocious metamorphosis were dose- and age-dependent when pill was post-natally applied. Pre-natal application of juvenile hormone III or its agonist, pyriproxyfen, following treatment with PII or PIII, did not influence the precocene effects on wing induction or inhibition, respectively. Post-natal treatment with the juvenile hormone and pyriproxyfen, subsequent to PIII, reversed the precocious metamorphosis effect but not wing inhibition. This differential result, with an identical rescue protocol, suggests that PIII induction of precocious adult development arises as the result of the selective destruction of the corpus allatum cells and a lowered JH titre. However, the property of PIII that promotes the development of wingless forms appears unrelated to this decrease in juvenile hormone titre. (C) 1996 Wiley-Liss, Inc.