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.
Tension is a skeletal-muscle reaction that ordinarily facilitates movements such as walking, talking or writing. However under the pressure of a stressful situation the fight or flight reaction often results in excessive and unnecessary muscle activity, which is Tension..elaxation is defined as the elongation (lengthening) of muscle fibers, the absence of tension. There are some 1,030 separate skeletal muscles in your body, almost half your body weight. When you perceive an intensely stressful event, these muscles immediately contract.