for the same purpose. The MEXICAN COCHINEAL, Coccus cacti, which has driven the others out of the field, is also a species belonging to this group. It lives as a parasite upon the Nopal, or Cactus opuntia-a plant very common in Central America. The commercial importance of this insect is shown by the fact, that in 1850 no less than two million five hundred and fourteen thousand five hundred and twelve pounds of cochineal were imported into Great Britain alone; and as about seventy thousand insects are supposed to be contained in a pound of this substance, we may form some idea of the numbers annually destroyed. For many years the cultivation of cochineal was entirely confined to Mexico; but the insect has lately been introduced into Spain and the French possessions in Africa, with some prospect of success.

A fourth species, of great importance, is the LAC INSECT, C. lacca, an inhabitant of the East Indies, where it feeds upon the Banyan-tree, Ficus religiosa, and some other trees. To this insect we are indebted, not only for the dye-stuffs known as lac-dye and lac-lake, but also for the well-known substance called shell-lac, so much used in the preparation of sealing-wax and varnishes. In all these cases it is only the female insects that yield the coloring matter.

THE PHYTOPHTHIRIA.

The greater part of this tribe is composed of Aphides or Plant-Lice, whose extraordinary history renders them one of the most interesting groups of insects. They are all small animals, with a more or less flask-shaped body, furnished with six feet and a pair of antennæ, and usually with a pair of short tubes close to the extremity of the abdomen, from which a clear sweet secretion exudes. Both sexes are sometimes winged, sometimes apterous; and the individuals of the same species are often winged and apterous at different periods of the year. They all live upon plants, the juice of which they suck; and when they occur in great numbers, often cause great damage to vegetation. Gardeners and farmers are well aware of this. Many plants are liable to be attacked by vast swarms of Aphides, when their leaves curl up; they grow sickly, and their produce is certain to be greatly reduced. One striking instance is presented by the HOP-FLY, Aphis humuli, which in England alone has often done damage to the hops to the extent of millions of dollars, in a single year.

The sweet fluid which exudes from the tubular process of the abdomen of these insects is often in such abundance that it drops upon the leaves of the plants frequented by them, and even to the ground. It is well known by the name of honey-dew. Ants have a particular fondness for this fluid, and may constantly be seen upon trees and plants frequented by Aphides, stroking them with their antennæ, apparently to induce them to furnish a supply of the coveted fluid. From this circumstance the Aphides have been termed the Ant's Milch-Cows; and they are said to tend them with as much care as would be bestowed by a human farmer upon his cattle. Wasps also have been observed similarly engaged. The manner of propagation of these insects, which we have noticed in our Introduction to this Class, p. 539, is extremely curious, and has been the subject of immense research on the part of naturalists.

THE CICADARIA.

Nearly allied to the plant-lice are the Cicadaria, which include a great variety of insects, of which the COMMON FROG-Hopper of Europe, Aphrophora spumaria, is an example. This is a small insect, furnished with long hind-legs which enable it to perform most extraordinary leaps. The TREE-HOPPERS of this country, Membracidæ, of which there are several species, are small, mostly green, and take leaps of five or six feet.

The family of Fulgorina includes the Lantern-Flies, of which a large species inhabiting Guiana, the Fulgora laternaria, is said to emit considerable light in the dark. This light is produced from a singular prolongation of the head, which is common to this and many other species, exhibiting most extraordinary forms in some instances. A well-known example of the genus Fulgora is the F. candelaria, constantly to be seen in boxes of Chinese insects. Many of the Fulgorina are of a large size, and decorated with most brilliant colors; but they are all inhabitants of warm climates. The European species are small, and generally very dingy in their appearance.

The Stridulantia derive their name from the faculty they possess of producing a chirping

noise, which, as they are generally of large size, is often exceedingly loud and sometimes dis

LANTERN-FLIES.

agreeable. Nevetheless, the ancients, and particularly the Greeks, appear to have regarded this music, which is very unpleasant to modern ears, with feelings of great satisfaction; and the Cicada is often referred to with expressions of delight by the Greek poets. The apparatus by which the sound is produced consists of a sort of drum placed in a cavity on each side of the base of the abdomen; this is pulled inward by the action of a particular muscle, and on being again let loose its vibration produces a loud, sharp The drums are concealed by scalelike plates, which are sometimes so large as to reach nearly to the extremity of the abdomen.

tone.

The female lays her eggs in slits, which she cuts in the bark of trees by means of a curious saw-like ovipositor; the branches are generally so weakened by the operation

that they fall to the ground, when the larvæ burrow down to the roots of the trees, upon which

they feed, often occasioning considerable damage. They appear to occupy at least two years in their development. In America the cicadas have the general name of Harvest-Flies; they are also often improperly called Locusts. There are several species, one of which, the RED-EYED CICADA, C. septendecim, is remarkable on account of the popular notion that it appears only once in seventeen years, in the same locality, being supposed to pass the interval in its preparatory stages. Hence it is known in this country as the Seventeen-year Locust. This idea is, however, unfounded; some of these insects appear among us every year, and they have manifested themselves in vast numbers at irregular intervals of five to ten years. This insect is very different from the locust of the Scriptures; indeed, there appear to have been eleven different species of insect spoken of in the Bible as locusts, but all of which were of the grasshopper family.

THE CICADA.

ORDER 11. THYSANURA.

This order derives its name from the Greek thysanos, a fringe, and oura, a tail, and includes two families, the one called Poduridae, and the other Lepismida. The former comprises the Springtails, having a forked tail, which is usually bent under the insect; by means of its sudden expansion they effect a considerable leap. The latter have a long, spindle-shaped body, usually covered with silvery scales; they are often seen in the sash-frames of windows.

This small order-from the Greek mallos, wool, and phago, to eat-is composed of insects. bearing a general resemblance to the lice, with which, in fact, they are arranged by many authors. They differ from them in having the mouth always formed for biting, being furnished with a pair of hooked mandibles, and distinct upper and lower lips. Instead of sucking the blood of the animals on which they are parasitic, the Mallophaga devour the most delicate portions of their hair or feathers; frequently attacking these organs at the moment of their sprouting through the skin. They are especially common upon birds, few of them being free from such parasites; and some species also infest quadrupeds. As nearly every species of bird has at least one of these peculiar to itself, their numbers are by no means small, and they have been formed into numerous genera.

ORDER 13. ANOPLURA.

Neither the habits nor the appearance of the insects forming the present order-whose name is derived from the Greek anoplos, unarmed, and oura, a tail—are such as to render them particularly attractive objects. Small as they are, perhaps no other insects inspire so much disgust as Lice, being generally regarded as the concomitants of dirty habits. They have a flattened and semi-transparent body, with a distinctly separated head, which bears a pair of short, five-jointed antennæ, and one or two simple eyes on each side, and is furnished beneath with a soft, retractile proboscis, within which are four bristle-like organs.

These animals are all parasitic upon mammiferous animals, of which almost every species has its peculiar louse, while some of them harbor three or four distinct species. Four species inhabit the human subject, two of which are common, the HEAD-LOUSE, Pediculus capitis, and the BODYLOUSE, P. vestimentorum; the P. tabescentium has only been occasionally observed, but always in vast numbers, either causing or accompanying a complaint under which the patient appears gradually to waste away. Several instances are recorded in ancient authors of death being caused by this disease, which is termed phthiriasis, from the Greek phtheir, a louse. The Roman dictator, Sylla, the two Herods, the Emperor Maximian, and Philip II. of Spain, are said to have died of this loathsome malady.

These insects generally infest those parts of their hosts which are most thickly covered with hair, among which they creep about with ease by means of their grasping claws. They attach their eggs, which are of a pear shape, and called Nits, to the hairs, and the young are excluded in a few days. They undergo no metamorphosis, and are soon capable of reproduction; so that their numbers rapidly increase, when proper measures for their eradication are neglected.

1 and 1, Egg and Larva of Iulus; 2 and 2, Iulus; 3, Polydesmus; 4, Glomeris; 5, Geophilus; 6, Lithobius; 7, Scutigera Longicornis.

The small class of Myriapoda is in its general characters very closely allied to the insects, although in some respects it appears to approach the Crustacea. In the mature state, their bodies are generally elongated, and composed of numerous segments, the articulations of the body being similar, and bearing each one or two pairs of jointed legs. The head always has a pair of jointed antennæ, very similar to those of many insects, and behind the insertion of these, on each side, is a variable number of simple eyes, which, however, are sometimes wanting. The mouth, in its general structure, bears a considerable resemblance to that of the masticating insects, being furnished with jaws, palpi, and an upper and lower lip. In their internal anatomy these animals also exhibit a great resemblance to the insects. Their nervous system consists of a series of ganglia running along the ventral portion of the body, and usually united by a

double thread; the circulation is effected by a long, cylindrical, dorsal vessel. The species. are all unisexual. In some kinds the young, on first escaping from the egg, possess nearly ail the characters of their parents, although the number of segments and limbs is always less, and increases at each change of skin; but some, as the Iuli, undergo a sort of metamorphosis, coming from the egg either quite destitute of feet, or furnished with only three pairs of these organs, and it is not until after several moultings that they attain the same number of legs as their parents. This metamorphosis, such as it is, indicates the close alliance of these creatures with the insects; and many authors either include them in the class Insecta or retain them in a separate class. The Myriapoda form two orders, the Chilognatha and the Chilopoda; of the former there are over seventy species; of the latter about one hundred.

organs.

ORDER 1. CHILOGNATHA.

In these the body is generally of a convex form, composed of numerous horny arches, below which an immense multitude of little feet may be seen, whence the name of Millepedes, or Thousand-legs, by which these animals are commonly known, is derived. Each segment of the body bears two pairs of limbs, with the exception of the hindmost segment, which is destitute of such The antennæ are short, and composed only of seven joints, and the jaws are reduced to a rudimentary condition. The species are found to feed principally upon vegetable matters, generally when in a state of decay. Their movements, notwithstanding their immense number of legs, are always very slow, and they generally endeavor to escape danger by rolling themselves up into a ball. There are several families belonging to this group, but the best-known species is the GALLY-WORM, Iulus terrestris, often found, like the rest of the tribe, in damp moss, and sometimes crawling over the trunks of trees. The I. maximus of Brazil is often seven inches long. The Glomerida, belonging to this order, resemble wood-lice.

These animals are usually of a flattened form, and live in the earth or under stones. They run with considerable swiftness in pursuit of their prey, and can even progress backward by the assistance of their tail-like hind-legs, which at other times are dragged helplessly behind them. Their food consists of insects, which they seize with the powerful jaw-like organs attached to the lower lip. There are various kinds, but the most remarkable family is that of the Scolopendridæ, commonly called Centipedes: they are nocturnal in their habits, prey on insects, and are active and voracious creatures. Some of these, in tropical climates—as for instance the Malfaisante, a West Indian Scolopendra-grow to the length of six inches, and certain writers say to twice that size. Their bite is very painful, and sometimes fatal. The smaller and harmless species, common among us, are found at night concealed under timber or in holes in walls. The ELECTRIC SCOLOPENDRA, S. electrica, is a European species, luminous in the dark. The Geophilidae have almost thread-like bodies, some species of which are phosphorescent. The species of Scutigera have the body divided into fifteen segments, each bearing eight pairs of long multi-articulated legs; they are very active, and often lose some of their legs when touched. Those of the genus Lithobius have the body above and below divided into the same number of segments, each of which bears a pair of legs.