Synthesis and insect growth regulating activity of thiosemicarbazones of methyl 2‐pyridyl ketones

Thirty‐six thiosemicarbazones of methyl 2‐pyridyl ketone and of some other methyl ketones were tested on Dysdercus cingulatus, Drosophila melanogaster, Locusta migratoria, Aedes aegypti, Tenebrio molitor and Musca domestica. Several derivatives were toxic, delaying or preventing ecdysis. The structure‐activity relationship is discussed. The mode of action of these compounds appears to be different from that of juvenile hormones, anti‐juvenile hormones, or chitin biosynthesis inhibitors.