The relative importance of nervous and humoral pathways for control of corpus allatum activity in the adult Colorado potato beetle, Leptinotarsa decemlineata (Say).

To elucidate corpus allatum (CA) regulatory mechanisms under the influence of photoperiod and starvation in Leptinotarsa decemlineata, gland activities were measured in vitro by the short-term radiochemical assay. This data was substantiated with juvenile hormone (JH) titer determinations by using a physicochemical method or a radioimmunoassay. Under short-day conditions both neural and humoral factors may be involved in CA inhibition. This was indicated by the temporary activation of short-day glands after denervation in early prediapause and the gradual inhibition of active CA from long-day females implanted into short-day hosts. Studies with farnesenic acid as a precursor indicated that the last two steps in the biosynthetic pathway of JH are also diminished during humoral inhibition of the CA. Transfer of short-day beetles to long-day photoperiod completely activated the CA and this process was independent of CA innervation. Starvation leads to neural inhibition of intact glands but to possible stimulation of the denervated CA, since implanted glands in starved hosts were fully activated irrespective of the photoperiod.