COCCIDE, OR SCALE INSECTS;-COCHINEAL. 191 tribe; it has been introduced, however, along with its proper food, into Spain and Algiers, as well as into the hothouses of this country. About 800,000 lbs. weight of Cochineal are annually brought to Europe; each pound of which contains about 70,000 insects. The Lac of the East Indies, which is extensively employed in the composition of varnishes, the making of sealingwax, &c., is the product of another species of Coccus. The species which inhabit our own country, are important rather on account of the damage they commit, than the benefit they afford to Man. The bark of many of our trees often appears warty, by reason of a great number of small oval or rounded bodies, like a shield or scale, which are fixed to them, and in which no external traces of the insect are to be observed. These, however, are larvæ belonging to the tribe in question. Some of them are females; others young males, which are similar to them in form. At a subsequent period, they all undergo singular transformations. The males fix themselves to the plant, and pass into the pupa state, in which they remain completely at rest; and at last emerge as winged insects,-coming out of their cocoons backwards, with the wings extended flatly over their heads. The females, on the other hand, remain attached to the plant, and increase in size, in consequence of the development of a large number of eggs in their interior; but they undergo scarcely any other change. The eggs are deposited between the lower side of the body, and the surface to which it is attached; the latter having been previously covered with a sort of cottony secretion. The parent then dies, and her body dries up and becomes a solid cocoon, which covers the eggs. Here the eggs are hatched; and the young larvæ, which are at first active in their habits, quit their envelope, and ascend to the extremities of the branches; there they affix themselves by their sucking-beak, gradually increase in size, and lose their activity. In this condition they pass the whole winter; and it is not until the succeeding spring, that the characters of the sexes, which are henceforth to be so distinct, begin to show themselves. ORDER VII.-HETEROPTERA. 721. THESE Insects bear a close general resemblance to those of the last Order; but are distinguished by the characters of the anterior pair of wings, which are tough at their bases and membranous only towards their points, and which fold nearly hori FIG. 417-PENTATOMA. zontally, partly overlapping each other. The mouth is formed nearly on the same plan as that of the Homoptera; being adapted solely for suction. By far the greater number of the Insects of this Order feed, like the preceding, upon the juices of plants; but some of them prey upon other and weaker Insects; and a few species (of which the numbers, however, sometimes mul tiply to a great extent) suck the juices of larger animals. The majority of this Order are found in tropical climates; and the species that inhabit those regions, are mostly ornamented with a great variety of beautiful colours and markings, which often vie with those of the most splendid of the Beetle tribes. Many species, however, are of aquatic habits; and these are all of an obscure or black colour. Nearly all the terrestrial species have the power of emitting, when they are suddenly alarmed or touched, a powerful odour; which is of a pleasing character in some species, but which in others (as the common Bed-bug) is very disgusting. Many of them seem to eject a poisonous fluid into the wound which they make for the purpose of suction. In some species, the wings are altogether undeveloped; or the upper pair is wanting. The insects of this Order continue active, and require food, during all the stages of their existence. They may be divided into two sections, distinguished by their residence, and by the modifications of their structure in accordance CIMICIDE, OR BUG-TRIBE ;-HYDROMETRIDE. 193 with it; the GEOCORISE, or Land-Bugs;-and the HYDROCORISE, or Water-Bugs. 722. Section I. GEOCORISE. This section contains a large number of families; nearly all of which, however, bear a strong general resemblance to that which includes the common Bugs,the CIMICIDE. Some of the tropical species attain considerable size, being described as of the bulk of a Cockchafer; and they are much dreaded by the inhabitants of the regions they infest. Many of the Geocorisa, however, are vegetable-feeders; and it is among these, that the most brilliant colours are exhibited. The common Cimex lectularius, or Bed-bug, and its allies, never possess wings.-There is a curious group of very longlegged insects, which, though placed in this section, leads to the next; this is the family HYDROMETRIDE, some species of which may be met with on almost every pond or stream, skimming along the surface, and turning rapidly about, with the greatest ease and velocity. The form of the body strongly resembles that of a London wherry; the hind feet conjointly act as a rudder; and the motion is given by the two middle feet, which do not, however, dip into the water, but merely brush along its surface. The body is clothed on the under side with a fine coating of hairs, forming a sort of plush; which is evidently serviceable in preventing it from coming in contact with the water. 723. VOL. II. Section II. Of the HYDROCORISE, or true Water 194 HYDROCORISE, OR WATER-BUGS. FIG. 420. NOTO- Bugs, there are two families only. The NOTONECTIDE, or Boatflies, live almost entirely in the water, where they feed upon other aquatic insects; these they seize by means of their fore-legs. The legs of the hinder pair have a fringe of bristles along their edge; by which the surface, with which they strike the water in swimming, is greatly increased. Their general form is extremely well adapted for rapid progression in water; and it is from the peculiar aspect and movement of the body, that they have received the name of boat-flies or water-boatmen. The insects of this family swim on their backs; and the arrangement of all their organs has reference to this position. When stationary at the surface of the water, as is much their custom in calm hot weather, they very quickly obtain intelligence of the approach of danger, by means of their eyes, which are so placed that they are able to see both above and below the surface; and then, by a single stroke of their paddles, which are commonly stretched out at full length, they descend out of sight. Their motions are very quick in the element they are chily formed to inhabit; whilst on land they are scarcely able to walk. They can fly well; but they rarely exercise this power. The larva and pupa only differ from the imago in their smaller size, and in the deficiency of wings. When they descend into the water, the Notonectidæ carry down a supply of air for respiration, in a hollow which exists beneath the wings, when these are folded together.The NEPIDE, or Water-Scorpions, receive their name from the scorpion-like form of their fore-legs, which are efficient instruments for seizing their prey. They are in most respects similar in structure and habits to the insects of the preceding family; but their motions are much slower, their legs not being so advantageously formed for swimming. The species represented in the accompanying figure is a very common inhabitant of our ponds. FIG. 421. NEPA ORDER VIII.-DIPTERA. 724. THE two-winged insects constitute one of the most extensive Orders in the whole Class, not only in regard to the number of distinct species, but also from the occasional excessive multiplication of individuals of the same species. Many of them, also, have been constant attendants upon Man in all ages. They do not attract attention, however, from their size, for there are few that exceed an inch in length; nor is it on account of their beauty, for the majority of them are of dull colours; their forms, too, are rarely elegant; and of the habits and metamorphoses of a large proportion of them, very little is known. They owe the notice they have attracted, chiefly to the habits of certain species; which affect Man and the Domestic Animals, in various ways, both in their perfect and early states. However annoying these may be, it must not be forgotten, that other Diptera are of extreme service, in cleansing the surface of the earth of vegetable and animal impurities; and the carcass that is full of maggots would be much more prejudicial in its decomposition, than it is when principally eaten up by these voracious creatures. The mouth in the insects of this order is formed for suction, as already described (§ 616); but there are considerable varieties in the mode in which this is accomplished. Behind the wings are found a pair of moveable slender bodies, termed halteres, or balancers; these are probably the representatives of the second pair of wings. They are kept in continual motion, and are usually present even when the true wings are not developed. The Diptera all undergo a complete metamorphosis, as far as respects the comparative structure of the Larva and the perfect Insect; the former being generally cylindrical footless grubs, with no representatives of legs, except in a few species. But in many there is no proper transformation into the Pupa state; the skin of the larva not being thrown off, but hardening and contracting, so as to form a kind of cocoon. Within this, the body of |