Beginning collectors must know something about what insects are, how they live, behave, develop, and reproduce. Although there are many advanced texts written about any one of these topics, this book provides a very basic foundation for beginning entomologists. Understanding the principles of insect growth, development, morphology, and behavior allows us to more easily rear, collect, identify and, in the case of pest insects, control them.

Nearly 75 percent of all animals are insects. Scientists have described and given scientific names to about 920,000 species of insects in the world, which represent almost 85 percent of all known animal species. Just think - there are more different species of dragonflies than of all mammals combined. There are about 9,000 species of birds, but almost twice as many species of butterflies. No wonder you can find insects nearly everywhere.

The fact that more species of insects are known than all other animals and plants combined is phenomenal, but even that number does not represent all of the insects on Earth. Some estimate that the number of named and recorded insects is only a fraction of the total number of living insect species. Many are very small and hard to find. Many live in areas where collection and study are difficult. Still others are right under our noses and are just waiting to be discovered.

Scientists who study the fossil record have estimated that insects have been around for more than 350 million years, much longer than people. Some early insects were huge dragonflies with wingspans in excess of 3 feet; others were very small. Today, the largest insects have bodies that measure 3 to 4 inches in length and may have wings that span 6 or 8 inches, but insects have become very diverse as they have adapted to life on Earth. You'll find them in nearly every type of habitat, with truly amazing features and behaviors that allow them to live and thrive in these conditions. Insects' relatively small size, high reproductive potential, and diverse feeding habits allow them to become very successful animals in our world. They have not only developed ways to live in nearly every habitat, but they have developed the ability to feed on a vast array of foods.

The greatest challenge to learning how to identify insects properly will be learning the names of the various components of an insect's body. Beginners usually compare collected specimens with published photographs or line drawings of the insect. This is sufficient for the most basic identification, but because there are so many insects, a photograph of every one would be very cumbersome. Many are very similar either in color, size, or shape. Often small differences in how an insect is constructed determine whether it is one species or something entirely different. As a result, written keys are constructed that, if followed, will lead a student to the proper identification. The process of identification will be discussed in greater detail in a later section. For now, it is important to gain a working knowledge of the anatomy or morphology of an insect, so that written keys can be followed. For example, some references may be made to particular structures such as tarsi. To answer questions relating to tarsi, you should consult a line drawing of the leg of a typical insect to determine where tarsi are. Similarly, a general recognition of other parts of basic insect anatomy or morphology is required.

Compared to people, insects are constructed inside out and upside down. For example, people have skeletons inside their bodies to which muscles attach and allow movement. Insects have external skeletons (exoskeletons) and their muscles are attached inside to allow for movement. People have nerve cords running along their backs (dorsal), with hearts closer to the front of the body (ventral). Insects have dorsal hearts and ventral nerve cords.

You'll find many more differences between people and insects. A human has four appendages (arms and legs); an insect has six. People breath with lungs, insects breathe through tiny holes along the sides their bodies. The heart and blood of an insect are not important to moving oxygen in the insect body. Insects smell with their antennae, taste with their feet, and hear with special organs in their feet, abdomen, and sometimes antennae. Insects are the only invertebrates that have developed the ability to fly, although they have also mastered running, burrowing, jumping, climbing, swimming, and hopping.

Insects are successful and fascinating, because they are unique in so many ways. Collecting and identifying insects requires a basic understanding of insect anatomy (morphology), development, and physiology (digestion, reproduction, nervous system, circulation, and respiration), as well as behavior. We shall begin with how to distinguish an insect from its close relatives.