The Purple Treble-bar (Aplocera praeformata) is a moth of the Geometridae family. It is found from the Iberian Peninsula and France, through Western Europa, over Central Europa up to Russia. Its northernmost range is Southern Finland and the Baltic States. The subspecies Aplocera praeformata urbahni is found in Greece. In the Alps it is found to heights of up to 2,000 meters. It has a wingspan of 34–44 mm. Adults are on the wing from June to August. It has one generation a year. The larvae feed on Hypericum species, such as Hypericum maculatum and Hypericum perforatum.