Four synthetic juvenile hormone analogues (JHAs) with high morphogenetic activity on a variety of insects prevented embryonic development of Tribolium confusum to varying degrees when applied to freshly laid eggs. At 1 ppm (v/v) of the JHAs a few eggs hatched; however, some of the larvae died within a day of hatching. Older eggs were totally insensitive to JHA treatment even at higher concentrations. Larvae that hatched from these eggs appeared to be perfectly normal and continued to develop into apparently normal larvae.
