338 



THE POPULAR EDUCATOR. 



the delicacy and yet the power of the wings the splendour of 

 the colours, and elaborateness of pattern, whether expressed in 

 these gorgeous hues, or marking and chasings are all so exqui- 

 site that the class is a. general favourite with all. With man, 

 excellency in the execution of any one plan seems to be incon- 

 sistent with diversity ; but how different is it with the Creator. 

 As if to exhibit how unlimited might be the variety while the 

 ground-plan is the same, we find a greater number of species 

 in this class than in all the rest put together. One order of 

 insects, the Coleoptcra, has not less than 80,000 different kinds 

 known to, and already described by naturalists; and yet so 

 imperfectly has the search for these hiding and burrowing 

 insects been carried out, that it would not be a matter of sur- 

 prise if a few years should double the number of known species. 

 We shall describe the insects first, because they occupy a central 

 position, and follow so closely on to the class Myriapoda, that 

 some naturalists have included these latter in the class. The 

 Myriapods, however, show so marked a difference to the insects 

 in the greater number of rings, in the similarity of these to one 

 another, in the whole of them being furnished with limbs, and 

 in never presenting any traces of wings, that they may be well 

 classed alone ; while the name Insecta, or notched animals, is 

 confined to the true hexapod (six-legged) order. 



The reader must have seen insects so often that it seems 

 superfluous to describe their general form and constant pecu- 

 liarities; yet we are so often accustomed to see without ex- 

 amining, and to examine without noting, that perhaps the fact 

 that a fly or a gnat has six legs may be new to some persons 

 who have been plagued by these creatures all their summers. 

 The body, then, of a typical insect in its final and perfect 

 state consists of three well-defined divisions, called (beginning 

 from the front) the head, the thorax (chest), and abdomen. So 

 deep is the notch which divides them from one ar, other, and 

 so small is the stalk or connection which unites them in bees 

 and flies, that the divisions of the bodies of these insects 

 cannot have escaped notice. In beetles and butterflies, the 

 divisions, though not quite so marked, are evident enough, but 

 in such insects as crickets and plant-bugs they are traced with 

 some difficulty. To the head is deputed the faculty of sensation 

 and prehension ; to the thorax the office of locomotion ; while 

 almost all the functions of organic life, such as digestion and 

 reproduction, are delegated to the abdomen. The head is 

 variously shaped, commonly resembling a disc, and presenting 

 a flattened but still convex surface forwards, on the expanse of 

 which are situated two antennas or feelers. These are almost 

 constantly present, but their form is so modified in different 

 insects, that no general description can be given of them. 

 Usually they are jointed, but the numbers of the joints, their 

 relation, size, and shape, and all connected with them, are so 

 different in different families, that they form an important 

 means of distinguishing one family from the other. The 

 mouth opens on the bottom part of the edge of the disc, while 

 the large complex eyes cover the lateral edges, and extend 

 often both in front and to the middle line at the top of the 

 head. When this is not the case, it is no uncommon thing for 

 three simple eyes to be placed on the very apex of the head, 

 in the form of a triangle. These, however, are by no means 

 constant in all insects. The organs which, standing round the 

 mouth, minister to all the accessory functions of gaining and 

 swallowing food, have, though very diverse in shape, been har- 

 monised by the labours of entomologists so as to represent one 

 plan. There is in front the labrum, or upper lip, then two 

 pairs of jaws, one pair behind the other, but each single jaw 

 playing from the side to meet its fellow in the mia-line. 

 Behind these is the under lip, which is sometimes very com- 

 plex, being split into three or five divisions. Additional 

 feelers like the antennae, but usually smaller and of fewer 

 joints, are often placed both on the hind pair of jaws and the 

 lower lip. When the mouth organs are spoken of as lips and 

 lateral jaws, it must be remembered that these organs are so 

 much modified that in some insects the terms seem hardly 

 applicable. Thus, a reference to the illustration of the head 

 of that insect which is found too commonly in our metropolis 

 will show that the four jaws, though springing from separate 

 roots, are united to form a single style-like puncturing appa- 

 ratus, and this is enclosed in the lower lip, which is a, tube 

 through which juices are sucked. 



The head is so consolidated that it would at first siffht 



suggest the idea that it consists of but one ring, corresponding 

 with one annulus of a worm, and some have thought this was 

 really the case. Others, however, believe, and apparently with 

 reason, that short as it is in its fore and aft or axial diameter, it 

 nevertheless is compounded of at least six rings, each of which 

 has its pair of appendages. Thus, the first bears the eyes ; the 

 second, the feelers ; the third, the undivided labrum ; the 

 fourth, the maxillse ; the fifth, the mandibles ; and the sizth, 

 the more or less split and complex labrum. This view may 

 appear fanciful, especially when the large rounded areas of 

 pavement-like eyes are spoken of as appendages or limbs; but 

 if we follow the comparison to the almost precisely similar organs 

 in crustaceans, where they are sometimes set on long and jointed 

 stalks, it ceases to be so. 



The thorax, although it forms a more or less globular or 

 cubical box, which lodges the muscles which ply the legs and 

 wings, plainly consists of three rings or segments. This is appa- 

 rent, not only on account of the number of appendages, but also, 

 on examination, the plates of which it is composed show the 

 lines of junction by sutures on the outside ; while on the inside 

 the edges of these are doubled in so as to form ridges, to which 

 the muscles are attached. To the first segment, or prothorax, 

 are attached a pair of legs. They spring from below, and 

 are extended outwards. The second segment, or mesothorax, 

 has a pair of legs below, and generally a pair of wings, spring- 

 ing from the back. The hind segment, or metathorax, has 

 the same limbs as the preceding one. The legs are all 

 jointed, the joints being of beautiful structure. The limb 

 starts from a movable plate wedged in between the fixed plates 

 of the body ; this is called the coxa. Then comes a small 

 joint which assists in allowing the limb to be rotated, and is 

 called the trochanter. Beyond this is the femur, and to its 

 end is attached, by a joint which only permits of an up and 

 down movement, the usually long serrated or spined tibia. 

 A string of five beaded joints forms the foot, the last of which 

 is furnished with two curved hooks to lay hold on the minute 

 roughnesses in the surface over which the insect crawls. Besides 

 the claws, there are often two or three cushions of stiff hairs, 

 which, aided by a sticky secretion, are very good sustainers of 

 the light and strong creatures when they walk on the ceiling of 

 a room. This description applies to the limb when most deve- 

 loped, as there is a vast variety in the composition of the limbs 

 of insects. The legs are used not only for walking, but also for 

 cleaning the body, the antennae, and the wings. They are some- 

 times furnished with curious brushes and combs for effecting 

 this purpose. The use which the working bee makes of its 

 hind legs namely, to store lumps of wax upon them, and so to 

 carry a supply of this substance to its hive will also occur to 

 all bee-keepers. 



The reader will probably wonder why the wings have not 

 been spoken of as appendages to the body-rings. He will ask, 

 if the number of so-called appendages is made to determine the 

 number of rings of which the body is composed, why the wings 

 do not count for limbs whereby to determine the number of 

 the annuli of the thorax ? A careful comparison of these 

 organs throughout the class, with their mode of development, 

 has led naturalists to suppose that the wings are modified gills 

 corresponding to the gill covers of crustaceans, and not with 

 the limbs of these. If this correspondence be genuine, it is a 

 curious instance of how the same organ may have very different 

 uses in different animals. The skin or integument of insects 

 consists essentially of three layers. The outermost is a thin, 

 transparent membrane ; beneath this is the hard, horny-coloured 

 layer, to the inside of which the live vascular skin is applied. 

 The wing consists of an extension oi the outer layer into a long 

 bag, the two sides of which are smoothed down and applied to 

 one another so as to form one sheet, while this is strengthened 

 and kept in shape by a framework of stiff fibres derived from 

 the second layer. Derivatives from the blood system and the 

 respiratory system in some instances enter the fibres, but are 

 not conveyed into the membranous part of the wing, so that the 

 torn wing of an insect is never repaired. The pattern of the 

 framework of fibres, or nervures, as they are called, is well 

 worthy of study, not only because it is beautiful and made 

 much use of in describing a,nd distinguishing insects, but on 

 account of its wonderful adaptation to the requirements of the 

 wing, furnishing strength and resistance where strength and 

 resistance are required- The winsrs are very variously deve- 



