The role of neurosecretion in the photoperiodic control of polymorphism in the aphid Megoura viciae.

The location of the photoperiodic mechanism controlling the production of the sexual and parthenogenetic morphs by apterous parents was examined by selectively injuring the brain with an R.F. microcautery. Lesions destroying the Group I neurosecretory cells (NSC) in the protocerebrum abolished the response to changed daylength. Extensive damage to other NSC Groups, to the compound eyes and optic lobes was without effect. It is concluded that the Group I NSC are the effectors, secreting a virginoparapromoting substance; in its absence only oviparae are produced. Areas slightly lateral to the group I NSC are also required for the long-day response, indicating that this is the probable site of the neuronal photoperiodic clock which regulates the release of neurosecretory material (NSM) from the Group I cells.