Morphogenetic analysis of the effects of juvenile hormone analogues and other morphogenetically active substances on embryos of Schistocerca gregaria (Forskål)

One of the basic assumptions of the author's gradient-factor theory of insect morphogenesis is that the effects of the hypothetical gradient-factor on tissue growth can be reproduced by the juvenile hormone, not only during postembryonic development, but also in the course of embryogenesis (Novák, 1951 a, b, 1956, 1966). This concept was originally based on the more or less indirect evidence supplied by the findings of Pflugfelder (1947) in Dixippus morosus and by those of Novák (1951 b) in Oncopeltus fasciatus. Recently, however, direct evidence has been made available by the work of Sláma & Williams (1966) on Pyrrhocoris apterus and of Riddiford (1966) on Hyalophora cecropia. Using the ‘paper factor’ in the first case and cecropia oil in the second, the above authors succeeded in demonstrating that these substances were able to block embryogenesis when applied to the egg surface or to the female before egg-laying commenced.