Directions for Collecting and Preserving Insects. Charles V. Riley
portions of the globe, and that in the more tropical portions a vast number of species still remain to be characterized and named, and if we take further into consideration the fact that many portions of the globe are yet unexplored, entomologically, that even in the best worked up regions by far the larger portion of the Micro-Hymenoptera and Micro-Diptera remain absolutely undescribed in our collections, and have been but very partially collected, it will be safe to estimate that not one-fifth of the species extant have yet been characterized or enumerated. In this view of the case the species in our collections, whether described or undescribed, do not represent perhaps more than one-fifth of the whole. In other words, to say that there are 10,000,000 species of insects in the world, would be, in my judgment, a moderate estimate.
CLASSIFICATION OF HEXAPODS.
Seven orders of insects were originally recognized by Linnæus, namely, Neuroptera, Diptera, Hemiptera, Lepidoptera, Coleoptera, Hymenoptera, and Aptera. This classification was based on the organs of flight only, and while in the main resulting in natural divisions which still furnish the basis of more modern classifications, was faulty in several particulars. For instance, the Aptera, which included all wingless insects, was soon found to be a very unnatural assemblage and its components were distributed among the other orders. The establishment of the order Orthoptera by Olivier to include a large and well-defined group of insects associated with the Hemiptera by Linnæus, restored the original seven orders, and this classification has, in the main, been followed by entomologists up to the present time.
Fig. 1.—Pyramid showing the nature of the mouth, and relative rank of the Orders, and the affinities of the Suborders of Insects.
All insects are, in a broad way, referable to one or the other of these seven primary orders by the structure of the wings and the character of the mouth-parts in the imago, and by the nature of their transformations.
Some of these orders are connected by aberrant and osculant families or groups, which have by other authors been variously ranked as independent orders, but which, following Westwood substantially, I have considered, for convenience, as suborders. (See Fifth Report, Insects of Missouri, etc., 1872.)
In the article just cited, I made use of the accompanying diagram in the form of a pyramid (Fig. 1), which gives a graphic representation of the distinguishing characters and the relative rank as usually accepted, of the orders and suborders.
Full discussion of the different classifications is unnecessary in this connection. Authors have differed in the past and will differ in the future as to what constitutes a natural system, and it would require many pages to give even a brief survey of the various schemes that have been proposed. As I have elsewhere said, “We must remember that classifications are but a means to an end—appliances to facilitate our thought and study—and that, to use Spencer's words, ‘we cannot, by any logical dichotomies, actually express relations which in nature graduate into each other insensibly.’ ”
The most philosophical, perhaps, of the more modern systems of classification is that of Friedrich Brauer, who has carefully studied the subject, and has given us an arrangement consisting of sixteen orders. This has many merits and has been adopted, with slight modifications, by Packard in his “Entomology for Beginners,” and by Hyatt and Arms in their recent and valuable text-book “Insecta.” Comstock, in his “Introduction to Entomology” strongly recommends Brauer's classification, but for reasons of simplicity and convenience adheres to a modification of the old classification of Westwood.
For purposes of comparison the classification by Hyatt and Arms, which is substantially that of Brauer, may be introduced.
In linear arrangement it is as follows:
| I. | Thysanura (Spring-tails, etc.). |
| II. | Ephemeroptera (Ephemeridæ; May-flies). (=Plecoptera Pack.) |
| III. | Odonata (Libellulidæ; Dragon-flies). |
| IV. | Plecoptera (Perlidæ; Stone-flies). |
| V. | Platyptera (Termites, Mallophaga, etc.). |
| VI. | Dermaptera (Forficulidæ; Earwigs). |
| VII. | Orthoptera (Locusts, Grasshoppers, etc.). |
| VIII. | Thysanoptera (Thripidæ; Fringe-wings). |
| IX. | Hemiptera (Bugs). |
| X. | Coleoptera (Beetles). |
| XI. | Neuroptera (Sialidæ, Hemerobiidæ; Lace-wings, etc.). |
| XII. | Mecoptera (Panorpidæ; Scorpion-flies). |
| XIII. | Trichoptera (Phryganeidæ; Caddis-flies). |
| XIV. | Lepidoptera (Butterflies and Moths). |
| XV. | Hymenoptera (Bees, Wasps, etc.). |
| XV. | Diptera (Two-winged flies). |
The relationship of these orders cannot be indicated in a linear arrangement, and is admirably shown by Hyatt and Arms by means of diagrams which I reproduce (Figs. 2, 3.)
Fig. 2.—Scheme illustrating origin and relationship of Orders. (After Hyatt.)
The relation of these sixteen orders to the older, septenary scheme is shown by the following arrangement:
| 1. Hymenoptera | Hymenoptera XV. | |||
| 2. Coleoptera | Coleoptera X. | |||
| 3. Lepidoptera | Lepidoptera XIV. | |||
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