A hormone causing pupation in the blowfly calliphora erythrocephala

Excellent descriptions exist of the morphological and chemical changes in the metamorphosis of insects. But until the last few years practically nothing was known about the actual forces which induce, initiate, or control moulting and pupation. In growth and metamorphosis of vertebrates the dominant controlling role of hormones becomes more and more obvious. It is especially in changes which concern simultaneously the whole body that the action of hormones is involved. The metamorphosis of insects consists also of profound changes on the whole animal which manifest themselves even more abruptly than do analogous processes in vertebrates. But it was only about 10 years ago that the action of a hormone in the metamorphosis of insects was suggeste for the first time by Kopeć (1922). The matter was raised again by von Buddenbrock (1930, 1931) and Koller (1929), a preliminary report having appeared in Koller’s survey on hormones in invertebrates. Recently new evidence has been brought forward by Bytinski-Salz (1933) and Bodenstein (1933,a andb ). The present position of the problem is given in an excellent review by Bodenstein (1933,b ), and he comes to the conclusion that the action of hormones in insect metamorphosis can be shown to be very probable from several facts, even if definite proofs are still lacking. It may be mentioned here that both Koller and Bodenstein failed to recognize the important and convincing results of Kopeć. A preliminary report of the present paper appeared in ‘Nature’ (Fraenkel, 1934).