From the preface to the first edition " Our object is to incorporate in one Volume octavo a Catalogue of all the known Insects of the order Lepidoptera inhabiting Great Britain; illustrated throughout with figures, reduced, where necessary, to a small size, but with a degree of accuracy that will enable the Entomologist to fix at once upon any particular species he may wish to define."
And from the preface to the present edition " A RE-ISSUE of this work being requires, it has been thought advisable not to alter either the names or numbers employed to distinguish the various species in the former edition, to which constant reference has been already made in works published since its first appearance, and of which the change or transposition would lead to much confusion.......It is further purposed to add a certain number of Supplemental Plates, illustrating speices discovered since the publication of the former edition, together with a synoptic list of the whole of the species, in order to shew their distribution into families, and the position of the supplemental species, and of those whose generic classification has been modified."