Effect of exogenous JHI on imaginal determination in Aeshna cyanea

Last instar larvae of Aeshna cyanea injected with 8 μg or more JHI before the end of the fourth ocular stage (day 7 or 8 of the instar) became perfect supernumerary larvae which indicates that adult determination does not occur before this time. When JHI is applied later (days 9–13) larval-adult intermediates are formed. It seems, therefore, that imaginal programming takes place at the end of the fourth ocular stage and might be correlated with the first ecdysone peak which occurs at the same time.