silky envelope spun by the larvae of many insects to protect pupas and by spiders to protect eggs
蛹を保護したり、蜘蛛が卵を保護するための、多くの昆虫の幼虫によって紡がれる絹のような包み
cocoon
retreat as if into a cocoon, as from an unfriendly environment; "Families cocoon around the T.V. set most evenings"; "She loves to stay at home and cocoon"