The period during which the _Lepidoptera_ remain in the chrysalis state varies very considerably in different species, and also depends more or less on the temperature. As a rule, when a caterpillar pupates before the end of the summer, it remains dormant in the pupal condition for only a few weeks; but, if late in the summer or in the autumn, it remains in this condition throughout the winter, and emerges in the following spring or early summer. Both these conditions are illustrated in the life history of the Large White or Cabbage Butterfly--an insect with which we have already become acquainted. We get two distinct broods of this butterfly every year, the first appearing in May and the second in August. The eggs of the first brood hatch in about a fortnight, and the larvae are full grown about four weeks later. These then change to chrysalides, from which the perfect insects (the second brood) emerge in a few weeks--the period varying slightly with the temperature of the season. From the eggs of this second brood we get another invading army of cabbage eaters that change to pupae late in the summer. These remain dormant till the following April, and may be found in numbers throughout the winter, attached to the walls and fences of kitchen and market gardens. If, then, the pupae of the same species are so influenced by the temperatures of the seasons, can we limit or prolong the period of quiescence by subjecting them to high or low temperatures artificially produced? Most certainly we can; and every practical entomologist knows how to obtain the perfect butterflies and moths of certain species long before their appointed times, or, if he desires it, to compel them to remain in their dormant stage long after the natural period has terminated. Sometimes an enthusiastic insect hunter obtains a large number of what we may term 'winter pupae,' by collecting and breeding various species. He also anticipates a number of successful captures of perfect insects during the following summer. Thus, from two distinct sources, he obtains a goodly assortment of butterflies and moths, the setting, preserving, and arranging of which entails an immense amount of home work. Under such circumstances he will sometimes endeavour to cause some of his pupae to emerge before their accustomed time, so that he may get some of his insects 'on the boards' before his field work is in full swing, and so avoid a rush, or prevent the loss of insects that will be spoiled before he has time to take them in hand. This process of hurrying up his pupae he calls 'forcing,' and simply consists in keeping them for a time in a warm room or hothouse where the high temperature is pretty constant.