Published online by Cambridge University Press: 10 July 2009
The embryonic development of Dysdercus fasciatus Sign. is described in terms of 15 arbitrary stages based on external morphological characters. The effects of treating eggs early in development with juvenile hormone and a mimic (JH) are then described in terms of the stages at which embryonic development is arrested and the resulting morphological aberrations are summarised. The effects of the treatment of two strains of D. fasciatus with two JH (Law's mimic and Ayerst synthetic juvenile hormone) are described and compared in terms of both the hatchability of the eggs and the stage distributions of the arrested embryos. Law's mimic was more effective than Ayerst SJH in preventing egg hatch, and the Malawi strain was less susceptible than the Reading strain. Embryonic development was never arrested earlier than the commencement of blastokinesis (Stage VIII). After treatment with Ayerst SJH most embryos of both strains were arrested during dorsal closure (Stages XI-XII) or at the time of eclosion (Stages XHI-XIV). Treatment of the Reading strain with Law's mimic resulted in the majority of embryos being arrested during blastokinesis (Stages VIII-X) at all doses. Examination of the timetable of development in both control and treated eggs reveals a dramatic reduction in developmental rate in treated eggs at the commencement of blastokinesis. It is suggested that JH may act on eggs of D. fasciatus in three ways: interference with eclosion, differentiation and the embryonic movements during blastokinesis.