A study has been made of the biology of Depressaria conterminella, Zell., the most important willow-shoot moth occurring in commercial willow beds of Lancashire and Cheshire.

The eggs are laid in June-July in bark crevices on the stocks near the level of the soil. Hatching takes place in the following spring, beginning about the time the buds open. The eggs are described.

On hatching the larvae travel to the opening buds. First instar larvae tunnel through the outer leaves into the buds, but larvae in the later stages crawl between the leaves, spinning them together to form a feeding shelter. Larvae have four instars and at the third ecdysis there is a marked colour change. Both larval forms are described. In the course of feeding each larva destroys 3–4 shoots. Infested shoots are illustrated. Pupation takes place in the soil and adults emerge after about three weeks.

The habits of the moths are described. The species is univoltine and no instance of parasitism has so far been observed. A list of other Lepidoptera bred from the shoots of willows is given.

The nature of the crop does not permit of costly control measures. The study of the biology suggested that infestation might be checked by delaying harvesting until after the larvae hatched. In an experiment in the field it was found possible to reduce infestation from over 40 per cent. to under 5 per cent. by this method. Infestation was also reduced by burning waste hay over the rows of willow stocks during the dormant season.