Effect of a juvenoid on embryonic development of Earias fabia (Stoll) (Lepidoptera: Noctuidae)

Eggs of Earias fabia were treated with three different quantities of a juvenoid, 6–7 epoxy-3-ethyl-1-(p-ethyl phenoxy)-7 methylnonane at 5 distinct stages. These were: (a) before blastoderm formation; (b) before gastrulation; (c) before segmentation; (d) before blastokinesis; and (e) just after blastokinesis. The effect on embryonic development was studied. If sufficient hormone is administered early enough, development may be arrested at stages as early as blastoderm formation. With moderate and smaller doses, developmental arrest mostly occurred at certain well-defined stages, such as germ-band formation; before blastokinesis; post blastokinesis; when the embryo assumes its larval form; at the time of chitin formation and during embryonic moulting. Observations also bring in focus the importance of the quantity of hormone and its relationship to the speed of its action. Toxic action is apparent when eggs are treated with relatively larger quantities of the compound: application of juvenoid to younger stages causes fewer deaths.