Cocoon

Cocoon, the silken sheath spun by the larvæ of many insects in passing into the pupa or resting stage. The cocoon proper is due to the secretion of special spinning glands, situated anteriorly or posteriorly, but larval hairs and foreign objects of many kinds may also be utilised. The amount of secretion, the arrangement of the threads, and the completeness of the covering vary very widely; nor is the presence of any cocoon whatever essential to the pupa stage. The most typical and perfect cocoons are those of many moths, a familiar example being that of the silkworm. The delicacy, neatness, and labour exhibited by these last silken robes make them as marvellous as they are useful. See CATERPILLAR, CHRYSALIS, INSECTS, and especially SILK.