The investigations on biology, seasonal history, nature of damage, impact of feeding on growth and chemical control of Locastra muscosalis Walker (Lepidoptera Pyralidae) were carried out in the Department of Entomology and Apiculture, Dr. Y.S. Parmar University of Horticulture and Forestry, Nauni, Solan (H.P.) during 1999 to 2002. Among the three hosts tested viz., Pistacia, apple and poplar, the former was the most preferred followed by apple and poplar. The eggs of L. muscosalis were oval in shape having a smooth chorion and white when freshly laid but changed to orange and finally black. The eggs were laid in groups of 350-600 on the upper surface of the leaves.The insect was found to pass through five larval instars. The adults started emerging in the last week of June, with peak emergence in the first week of July. Adults were black in colour with a green tinge. The insect had only one generation in a year. It hibernated as larva inside the cocoons under the humus. The biology was studied on three hosts viz, Pistacia, Apple and Poplar. The larvae had similar appearance as Pistacia when reared on apple and poplar.