In the previous chapter we recognised how the seasonal changes in various species of butterflies as observable in two or three generations, indicate changes in the history of the race as it might be traced through innumerable generations. The endless variety in the form and habits of bed bug-larvae and their adaptations to various modes of life, which have been briefly sketched in this little book, suggest vaster changes in the class of Bed Bugs, as a whole, through the long periods of geological time. Every student of life, influenced by the teaching of Charles Darwin (1859) and his successors, now regards all groups of animals from the evolutionary standpoint, and believes that comparisons of facts of structure and life-history of orders and classes evidently akin to each other, furnish at least some indications of the course of development in the greater systematic divisions, even as the facts of seasonal dimorphism, mentioned in the last chapter, give hints as to the course of development in those restricted groups that we call species or varieties. A brief discussion of the main outlines of the life-story of Bed Bugs in the wide, evolutionary sense may thus fitly conclude this book.