For many years the most pressing demand of teachers and learners in entomology in this country has been for a handbook by means of which the names and relative affinities of insects may be determined in some such way as plants are classified by the aid of the well-known manuals of botany. But, as the science of entomology is still in its infancy, the preparation of such a handbook has been impossible. Excellent treatises on particular groups of insects have been published; but no general work including analytical keys to all the orders and families has appeared. It is to meet this need that this work has been prepared.

The reader must not expect, however, to find that degree of completeness in this work which exists in the manuals of flowering plants. The number of species of insects is so great that a work including adequate descriptions of all those occurring in our fauna would rival in size one of the larger encyclopedias. It is obvious that such a work is not what is needed by the teachers and students in our schools, even if it were possible to prepare it. An elementary work on systematic entomology will always of necessity be restricted to a discussion of the characteristics of the orders and families, and descriptions of a few species as illustrations. Complete synopses of species will be appropriate only in works treating of limited groups. It is believed, therefore, that it would not be wise to materially change the scope of the present work even if it were possible to describe all of our species.

Although much pains has been taken to render easy the classification of specimens, an effort has been made to give the mere determination of the names of insects a very subordinate place. The groups of insects have been fully characterized, so that their relative affinities may he learned; and much space has been given to accounts of the habits and transformations of the forms described. As the needs of agricultural students have been kept constantly in view, those species that are of economic importance have been described as fully as practicable, and particular attention has been given to descriptions of the methods of destroying those that are noxious, or of preventing their ravages.

An effort has been made to simplify, the study of insects as much as possible without sacrificing accuracy in the descriptions. Only such morphological terms have been used as were necessary to accomplish the object of the book in a satisfactory manner. And so far as possible a uniform nomenclature has been used for all orders of insects. The fact that writers on each order of insects have a peculiar nomenclature has been a serious obstacle to the progress of entomology; this is especially true as regards the nomenclature of the wing-veins. It has been necessary for the student in passing from the study of one order of insects to that of another to learn a new set of terms; and in many cases writers on a single family have a peculiar nomenclature.

The present writer has endeavored to remove this obstacle by making a serious study of the homologies of the wing-veins, and by applying the same term throughout the work to homologous veins. The result is that the student is required to learn only one set of terms; and in applying these terms there will be brought to his attention in a forcible manner the peculiar modifications of structure characteristic of each order of insects. Heretofore, with a different nomenclature for the wing veins of each order such a comparative study of the various methods of specialization has been beyond the read of any but the most advanced scholars.

The principal features of the method of notation of wing-veins proposed by Josef Redtenbacher has been adopted. But as the writer's views regarding the structure of the wings of primitive insects is very different from those of Redtenbacher, the nomenclature proposed in this book is to a great extent original. The chief point of difference arises from the belief by the present writer that veins IV and VI do not exist in the Lepidoptera, Diptera, and Hymenoptera; and that, in those orders where they do exist, they are secondary developments. The reasons for this belief are set forth at length in my essay on Evolution and Taxonomy.

In this essay there was proposed a new classification of the Lepidoptera, which was the result of an effort to work out the phylogeny of the divisions of this order. This classification has been further elaborated in the present work. In the other orders but few changes have been made from the more generally accepted classifications. It is more than probable however that when the taxonomic principles upon which this classification of the Lepidoptera is based are applied to the classification of the other orders radical changes will be found to be necessary.

A serious obstacle to the popularization of Natural History is the technical names that it is necessary to use. In order to reduce this difficulty to a minimum the pronunciation of all of the Latin terms used has been indicated, by dividing each into syllables and marking the accented syllable. In doing this the well-established rules for the division of Latin words into syllables have been followed. It seems necessary to state this fact in order to account for differences which exist between the pronunciations given here and some of those in certain large dictionaries recently published in this country.

Nearly all of the wood-cuts have been engraved from nature by the Junior Author. As the skill which she has attained in this art has been acquired during the progress of the work on this book, some of the earlier-made illustrations do not fairly represent her present standing as an engraver. But it does not seem worth while to delay the appearance of the book in order to re-engrave these figures; especially as it is believed that they will not be found lacking in scientific accuracy. The generous appreciation which the best engravers have shown towards the greater part of the work leads us to hope that it will be welcomed as an important addition to entomological illustrations.

Although the chief work of the Junior Author has been with the pencil and graver, many parts of the text are from her pen. But in justice to her it should be said that the plan of the book was changed after she had finished her writing. It was intended at first to make the book of a much more elementary nature than it is in its final form. It has seemed best, however, to leave these parts as written in order that the work may be of interest to a wider range of readers than it would be were it restricted to a uniform style of treatment.

The figures illustrating the venation of the wings of insects have been drawn with great care under the writer's direction by Mr. E. P. Felt and Mr. R. H. Pettit. About one half of those in the chapter on Lepidoptera were drawn by Mr. Felt; the others in this chapter and those in the chapters on Diptera and Hymenoptera were drawn by Mr. Pettit.

I wish also to acknowledge the help of my Assistant Mr. A. D. MacGillivray, to whom I am indebted for much aid in bibliographical researches and in many other ways; also, that of Dr. A. C. White of the Cornell University Library, who has generously given much time to determining the etymologies of many of the more obscure words the pronunciations of which are indicated in the text.

To the authorities of Cornell University the authors of this book are under deep obligation for aid and encouragement. The preparation of the work would not have been possible but for the liberal grants which they have made for the purchase of specimens and books.

        JOHN HENRY COMSTOCK.

        ENTOMOLOGICAL, LABORATORY,

        CORNELL UNIVERSITY, December, 1894.