The Functions of the Corpus Allatum in Rhodnius Prolixus (Hemiptera)

It has been shown in earlier papers (Wigglesworth, 1934, 1936, 1940) that metamorphosis in Rhodnius takes place when the corpus allatum ceases to secrete the ‘inhibitory’ or ‘juvenile hormone’. There was no evidence for the existence in this insect of a ‘metamorphosis hormone ‘which promotes the development of imaginai characters. Growth and moulting are induced at all stages of development by a ‘moulting hormone’ (what is called by Scharrer & Scharrer (1944) a ‘growth and differentiation hormone’) secreted in the dorsum of the protocerebrum. When this hormone alone is acting, the latent imaginai characters are realized and metamorphosis occurs. When the ‘juvenile hormone’ from the corpus allatum of the early nymphal stages is present in addition, it causes the preferential development of nymphal characters and thereby suppresses those of the adult.