How to Use This Book

Identification. The identification of insects is not fundamentally different from the identification of birds, mammals, ferns, or other forms of life. It is simply a matter of knowing what to look for, and being able to see it. Three things complicate the problem of insect identification: there are so many different kinds of insects (some 88,600 species in North America), many are small and the identifying characters often difficult to see, and many undergo rather radical changes in appearance and habits throughout their life cycle, with the result that one may learn to recognize an insect in one stage but be unable to recognize it in another.

It is impossible in a book of this size to include all the information necessary for identifying the huge numbers of insects, so we carry the identification only to the family level (further in a few families). This reduces the problem considerably, but adds a complicating factor: many families consist of species that vary greatly in size, shape, and color. Identification in such cases must be based on certain structural details rather than color and general appearance. We reduce the problem further here by dealing principally with adults and only incidentally with immature stages.

The part of this book dealing with identification is based primarily on an examination of the insect in the hand. After identifying an insect by a detailed examination of its structural details, one often can recognize it in the field without examining these details. Some means of magnification is needed for seeing many of the minute features of insect structure. A 10 X hand lens is sufficient in many cases, but a microscope (usually a stereoscopic microscope) is necessary for identification of many of the smaller insects.

Identification of an insect may be based on one or more characteristics: its general appearance (size, shape, and color), the form or character of various body parts (antennae, legs, wings, bristles, or other parts), how it acts (if it is alive when examined), where it is found (the type of habitat, and the part of the country), and sometimes such characters as the sounds it produces, its odor, or the hardness of its body. Many insects can be recognized by their general appearance as belonging to a particular order or group of families, but further identification often requires an examination of individual parts of the insect.

Identification of an insect is a process of progressively narrowing down the group to which the insect belongs. We suggest the following steps:

1. Identify the order to which the insect belongs. This is done by using the pictured key on the front and back endpapers. A comparison of the specimen with the first pair of alternatives will lead to further alternatives, and eventually to the order; if you are not sure at any step which way to proceed, try both alternatives. Then check your identification by consulting the paragraphs on Identification and Similar orders in the general account of that order, the information in the table on pp. 57-59, and the illustrations.

2. Identify the group of families in the order (if the order contains only a few families, proceed to step 3). The larger orders are variously subdivided, but the major groups in the order (suborders, superfamilies, etc.) are indicated in the introductory account (under Classification), and the distinguishing characters of each group are given at the beginning of the discussion of a group. If such a group is further subdivided, information will be given on the subdivisions, so that eventually the specimen can be narrowed down to a small group of families.

3. Identify the family. This is done by checking the paragraphs on Identification and also the accompanying black and white illustrations for the families in the group.

If the beginner will spend a little time studying the illustrations in this book and the information in the table on pp. 57-59, he should soon be able to recognize the order of most insects he finds — and further identification will be by the steps 2 and 3 indicated above.

Illustrations. This book contains one or more illustrations for most North American insect families, with diagnostic arrows pointing to the important distinguishing features. The families for which there are no illustrations are small or rare, and not very likely to be encountered by users of this book. A few illustrations are designed to explain the characters used in identification; the majority are intended to show the characters of individual families, and consist of drawings of individual insects and isolated body parts.

Most of the illustrations have been made of a particular species, though the species (or genus) is not always indicated. These species were selected because they are more or less typical of the group, or are the ones most likely to be encountered. Some of the simpler drawings are rather generalized and intended to represent a group of species rather than any particular one. Some families are illustrated solely by drawings of isolated body parts; the insects in such families are similar in general appearance to those in related families illustrated by drawings of entire insects.

The arrows on the illustrations indicate major diagnostic characters; usually there are italics in the accompanying text or legend page to link with the pointed arrows. Arrows ending slightly off a figure are intended to call attention to general features

(shape, number of segments, etc.) of the body part indicated. Two or more arrows from a common point refer to a single character. Arrows are generally omitted when they would not indicate clearly such easily observable features as general shape and color.

The actual size of most insects illustrated is shown by a line near the drawing; for some large insects this line is in 2 or more sections. These lines generally represent body length (from front of the head to tip of the abdomen, or to the wing tips if they extend beyond the abdomen); horizontal lines in some cases represent wingspread. If there is no size line, information on size will be found in the text.

Terms, Abbreviations, and Symbols. Many terms referring to body parts or areas are defined where they are used. For terms not so defined consult the Glossary (p. 363).

A few abbreviations and symbols are used in the descriptions: FW, front wing; HW, hind wing; d\ male; 9, female. Measurements, unless otherwise stated, refer to body length. Smaller measurements are given in millimeters. Comparison of millimeter and inch scales is shown below.

All venational characters, unless otherwise stated, refer to the front wing. Any reference to the number of cells in a specific part of the wing refers to the number of closed cells (those not reaching the wing margin) unless otherwise indicated.

Geographical Coverage. This book covers the families of insects occurring in North America north of Mexico. The characters given for each group apply to North American species, and may not apply to all the species occurring elsewhere. The terms "N. America" and "N. American" refer to that portion of the continent north of Mexico. Groups for which no information is given on geographic range are widely distributed in North America. Most of the figures given for the number of species in a group are conservative estimates.

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