The beetles (order Coleoptera) make up a very distinct and natural group of insects, characterized by the horny or leathery texture of their forewings, or "elytra," which serve as cases for the folding membranous hind wings alone used in flight. These elytra, when closed, usually cover the whole hind body. They are strengthened with ridges around their edges, and marked with a series of longitudinal furrows and often also with impressed dots. The hind wings are sometimes very small or wanting; in such cases the elytra are often fused together along their middle edges (suture). The head is usually extended from behind forward, having therefore a large crown and a small face; the feelers are very inconstant in form; the mandibles are always developed as strong biting jaws; the prothorax is free and movable; its tergite (pronotum) is a very prominent feature in all beetles, reaching back to the origin of the elytra.

The beetles undergo a complete metamorphosis, and the larvæ, called "grubs," have various shapes, while the pupa is "free," that is, closely similar in development and appearance to the adult. Beetles are world-wide in distribution and more than 100,000 species have been catalogued. They are divided into a great number of families, among which those mentioned below contain the most noteworthy forms.

The tiger beetles are large-headed, predacious forms, most numerous in the tropics, which live in holes in the soil and rush out to seize passing prey. The ground beetles (Carabidæ) are a very extensive family, represented in all parts of the world, and are insect hunters, destroying hosts of injurious insects. Most of them are black or brown. The Dyticidæ and Hydrophilidæ are aquatic families, including some of the largest and fiercest of carnivorous beetles, the terrors of ponds and marshes, where they prey not only on other insects and their young, but on tadpoles, small fishes, etc.; and their grubs are quite as savage. The rove beetles (Staphylinidæ) are a very large family of narrow, elongated species, which are very active; they feed mostly on small insects, worms and snails. The carrion beetles belong to the family Silphidæ, the smaller among which live in moss and under tree bark, and the larger genera contain the noted "burying beetles." Some groups of very minute, ground-keeping species lead to the familiar "ladybirds" (Coccinellidæ), a large and world-wide family of small, rounded beetles, usually brightly spotted, which frequent plants of all sorts, and feed chiefly on aphids. Some quaint superstitions pertain to these pretty insects, that should be attracted rather than repelled when they visit window gardens and greenhouses, which they will endeavor to clear of the "greenfly" and similar injurious plant lice. Passing over several inconspicuous families we come to the dermestids, very small, dark-colored beetles of elliptical outline, some of whose genera are among the worst of household pests, and have been spread by commerce throughout the civilized world.

Some of the dermestids are troublesome as museum pests; others attack food in the pantry, store, or warehouse. "Drugs do not escape their attack, species devouring even cantharides and tobacco; woolen and silk goods, feathers and furs, are ruined if left long exposed to their depredations; and one species is accused of biting young doves.... Anthrenus scrophulariæ, probably introduced into America from Europe, has received the names carpet beetle and buffalo bug, on account of its habit, both as larvæ and imago, of destroying carpets. This beetle measures about four-fifths of an inch in length, and is black, brick-red and white, the last crossing the back in two zigzag lines. The point of attack is the nailed-down edge or the lines of the seams."

Who has not been amused at the labors of the big black beetles that one meets in summer on dusty paths rolling balls of fibrous material. These "dung beetles" are the American cousin of the scarab of the ancient Egyptians, which typified to them many mystical ideas connected with life, present and eternal. With its shovellike head and broad forelegs the beetle gathers and compacts the material it wants, and begins to roll it, sometimes with the help, more often against the struggles, of another beetle toward a prepared nest-hole. Arrived there an egg may be inserted into it, and then the rounded mass is left as food for the grub to be hatched from the egg; if no egg is inserted, the ball becomes simply a mass of stored food to be eaten by its maker. Processes vary among the 7,000 or more known species of this cosmopolitan family.

Not all of this great family are dung beetles, however, or scarablike. Here belong the May bugs and June beetles that come blundering around lighted country residences in the evenings; and it is their fat white grubs that, hatched from eggs buried in the ground, devour the roots of the grass and other plants, spoiling the lawns and strawberry beds. The robin is their most effective enemy. Among thelesser genera are those of the rose bugs, hated pests of the horticulturist and fruit grower. In that section of the family known as the cetonians are found the giants of the race, the West African "goliaths," four inches long; the tropical American Hercules beetle, exceeding six inches long, half of which belongs to the forward-reaching horn of its helmet, the South American elephant beetle which is even more bulky, and several other giants, the males of which have the head ornamented with fearsome protuberances.

Other families of beetles are the Buprestidæ, whose larvæ are injurious to trees by boring into their wood; the Elateridæ, or snap beetles, which arch their bodies and leap when they happen to fall on their backs, and among which are found the many varieties of brilliant "fireflies" for which the American tropics are famous. The larvæ of the elaters mostly live in decaying wood, and are the justly hated "wireworms" of our gardens. Then there are the Meloidæ, that include the blister beetles, or oil beetles, one of which is the cantharides of the pharmacopœia; and there are a great many more.