A few butterflies and many moth species spin a silk case or cocoon prior to pupating, while others do not, instead going underground. A butterfly pupa, called a chrysalis, has a hard skin, usually with no cocoon.
4. tension - (physics) a stress that produces an elongation of an elastic physical body; the direction of maximum tension moves asymptotically toward the direction of the shear. natural philosophy, physics-the science of matter and energy and their interactions; his favorite subject was physics.
Medical Definition of dynamics. 1  1: a branch of mechanics that deals with forces and their relation primarily to the motion but sometimes also to the equilibrium of bodies. 2  2: psychodynamics. 3  3: the pattern of change or growth of an object or phenomenon personality dynamics population dynamics.