How To Know an Insect

What Kind of Insect Is It?

C. F. W. Muesebeck.

The Animal Kingdom is made up of a number of major divisions, or phyla. One of them, the Chordata, includes man and the other mammals, birds, reptiles, fish in fact, all the vertebrates, the creatures that have backbones.

By far the largest division from the standpoint of the number of different kinds, or species, it comprises is the Arthropoda. At least 8o percent of all known animals are arthropods. This phylum comprises invertebrate (back-boneless) animals that have a segmented body, jointed appendages, and a hard outer covering, or exoskeleton. It is in turn divided into a number of groups called classes, each of which differs in some fundamental characteristics from the others. One of these classes, known as Hexapods, or Insects, contains all the insects. Various members of other classes of Arthropods, especially such organisms as mites, ticks, spiders, scorpions, millipedes, centipedes, and sowbugs, however, are so commonly regarded as insects that it seems advisable to indicate the basic distinctions between these Several classes in a simple key.

A key is based on the process of elimination. In the key that follows, for example, one considers (as in entry number 1) the number of legs of the creature he wishes to identify. If it has five or more pairs, he consults entry 2 (as given at the right) ; if it has three or four pairs, he skips to entry 4. And so on.

Key to the Principal Classes of Arthropods.

1. With five or more pairs of legs................2.

With three or four pairs of legs.....................4.

2. Body wormlike; head not merged with the thorax and provided with one pair of antennae or with none.......................3.

Body not wormlike; head merged with the thorax and provided with two pairs of antennae:

Crustacea (crabs, lobsters, shrimp, sowbugs, etc.) (figure 1, next page).

3. Body segments each with only one pair of legs: Chilopoda (centipedes) (figure 2).

Most of the body segments each with two pairs of legs; Diplopoda (millipedes) (figure 3).

4. Body composed of two main divisions, the cephalothorax (fused head and thorax) and abdomen; four pairs of jointed legs; wings and antennae lacking Arachnids (spiders (figure 4), scorpions (figure 5), mites, ticks, etc.).

Body composed of three main divisions, the head, thorax, and abdomen; only three pairs of jointed legs; wings usually, antennae always, present; Insecta (all insects).

For purposes of orderly classification and to facilitate identification, each of these classes is divided into a number of orders, an order is broken down into families, a family is divided into genera, and each genus is composed of related species. Thousands of species of insects have thus far been described. Obviously each species must have a distinct name, and because many species are cosmopolitan the same name must be used for the same species everywhere. When the present system of naming animals was established about 200 years ago, most scientific books were written in Latin, and Latin was considered the universal language of science. The scientific names of animals, therefore, are in Latin or in Latin form. The name of each species consists of two words, the name of the genus to which the species belongs and a word, often an adjective, that stands for the species.

A froghopper producing its protecting mass of bubbles. Within, it is sheltered from the direct rays of the sun and kept moist by the foam.

Sowbug.

Centipede.

Millipede.