As to about forty thiourea derivatives and some thiol compounds, effects on pupation and imago emergence of housefly larvae were examined by feeding and dipping tests. As the result, it was elucidated that N-benzoyl-N’-(p-dimethyiamino)-phenylthiourea, 3-(p-chlorophenyl)-thioureide-propionic acid and N-(3,4-methyIenedioxy)-benzoyl-N’-(3’, 6’-dichloro-2’-methoxy)-phenylthiourea inhibited markedly the imago emergence, but inhibited the pupation little, Moreover, some of the effective compounds restrained the anterior inhibition, suggesting that the inhibitory activity was concerned with depriving of metals.