What Is the name of a particular group of people that assemble in the local forest in groups are know for their use of hallucinogens and their practice of nudity?

The group you are referring to is often associated with the modern neo-pagan and nature-based spiritual movements, commonly referred to as "Nature Worshippers" or "Earth Spirituality Practitioners." They may gather in forests for rituals that often include the use of hallucinogens and nudity as a means of connecting with nature and exploring consciousness. These gatherings can vary widely in practice and belief, reflecting a diverse range of philosophies and traditions.