Steadily over the next four days the silkworm produces a fine thread by making a figure of eight movement some 300,000 times, constructing a cocoon in which it intends to spend the chrysalis stage where it is in a state of sleep and casting off its skin. After this the pupae begin the sixteen days that would normally result in the miracle of transformation to a winged being - the moth. However, if the pupa (chrysalis) remains alive it will begin to secrete an alkali, which eats its way through the cocoon, ruining the silk threads. Therefore during the commercial production of silk, only enough adult moths are allowed to emerge to ensure continuation of the species. Most of the remainder of the silkworms are killed by heat, e.g. immersion in boiling water, steaming or drying in an oven.