Corpus allatum activity and the effects of juvenile hormone on oocyte development in azadirachtin-induced over-aged nymphs ofLocusta migratoria(L.)

Summary The corpora allata (CA) of azadirachtin (AZA)-induced over-aged 5th instar female nymphs of Locusta migratoria were relatively inactive during the first 20 days in the instar. They afterwards produced juvenile hormone (JH) III in vitro, coinciding with limited vitellogenic oocyte development. The basal rate of JH production and the length of the vitellogenic oocytes were lower in the over-aged nymphs, but the farnesoic acid (FA)-stimulated rate of JH production and volume of CA were higher than in normal adult females. Injection of massive doses of methoprene into the over-aged nymphs slightly enhanced vitellogenic oocyte development, which still remained incomplete. Chemical allatectomy by precocene III prevented, and injection of JH III or of methoprene restored, the limited vitellogenic oocyte development in the over-aged nymphs. Therefore, some factor other than JH shortage—possibly inadequate competence of the ovaries/ovarioles, would seem to limit vitellogenic oocyte development in over-aged nymphs.