Color, size, and markings of an insect, together with written information as to where it was found (locality) and what it was doing (behavior) allow an experienced entomologist to identify insects quickly. However, it should be stressed that this is not always a clear-cut process. Beginning entomologists should become familiar with the use of the order keys to avoid misidentifying insects that look alike. In addition, expertise in working dichotomous keys is a foundation for more in-depth identification (to the family, genus, or species level). The following chart depicts the current most commonly recognized orders of insects. In this publication we describe 24 common orders of insects, most of which can readily be collected in every state. Additional orders such as Protura, Diplura, Zoraptera, and Embioptera are rare and seldom encountered even by the most experienced collectors.

A dichotomous key is a tool that allows the user to determine the identity of insects based primarily upon what the insect looks like (its morphology). A key consists of a series of choices that lead the user to the correct name of a given insect. “Dichotomous” means “divided into two parts.” Therefore, dichotomous keys always give two choices in each step. In this book, we present a dichotomous key for the classification of adult insects into their proper orders.

Start at the beginning of the key, and as you study the insect in question, you will be given a set of two mutually exclusive choices. Depending upon the answer to the question, you will either learn the proper order of the insect or you will be directed to another set of questions.

Eventually your choices will lead you to the name of the insect order. Once an insect is identified to order, you can assume that much of the biology, distribution, and key behaviors of the insect in question, are similar to other insects in the order.

Experience in working through the keys will help tremendously. Sometimes particular specimens are difficult to classify, even with the key. On occasion, a rare specimen may not easily key out. Do not be discouraged. Consult with a person who is well trained in classification, or contact a professional entomologist to assist. Remember that the following key is designed for adult specimens only. It will not work for immature insects.