agreeable sources, with aqueous vapour, and bring in the requisite quantity of oxygen. It is almost impossible to get in a supply of ozone, except in those places which are not exposed at once to the influence of great cities; its absence is a proof of adulteration, but we are at present too ignorant of the influence of ozone to write about it in a dogmatic manner. It is not the presence or absence of a minute fraction of CO, which makes all the difference between a pure or an impure air, but it is the concomitants of that fraction. It is possible that the power of oxygen to pervade the tissues, to enter the circulation by endosmosis, and to give out CO, by exosmosis, is interfered with by the smallest possible alteration in the quantities of the atmospheric constituents, whilst the materials exhaled are undoubtedly poisons to the human frame; but whilst the increase or decrease of the CO2 is of no absolute consequence, its presence, when that presence is caused by the respiration of flesheating animals, is a mark of the presence of other more deleterious matter which is not so easy of detection, but which is removed with the CO2 The amount of CO, must be raised 250 times to reach the proportion of one per cent. An atmosphere which contains one per cent. of CO2 gives headache; a candle is put out when placed in an air containing two and a half per cent., and four per cent. would be fatal to human beings. The quantity of CO, exhaled by an adult in the course of an hour is about 06 cubic feet: this quantity is increased by active work, and is influenced by diet, by age, weight, and sex. Children exhale more than adults, weight for weight, and girls more than boys; it is probable that we may assess their adulterating power at 0'40 cubic feet per hour for each individual. The problem before us is how to prevent the quantity of CO, rising from 04 to something above 06, as this will be the best means for diminishing the organic matters and watery vapour which also accompanies the excess of CO2

Practical Lessons on Ensect Life. No. IV. THE COLEOPTERA, OR BEETLES. BY THEODORE WOOD, M.E.S., Joint Author of 'The Field Naturalist's Handbook.' PART I.

BESIDES their primary division into Orders, in

sects are further subdivided into classes of lesser importance, which are severally known as groups, or divisions, families, and genera. These terms I will now endeavour to explain.

A group comprehends such insects in any one order as agree in some essential point of structure, such as the formation of the mouth, or the antennæ, although their general form and habits may be widely dissimilar. Thus the members of the Clavicornia, or ' club-horned' insects, one of the chief divisions of the coleoptera, are included in a single group on account of the structure of their antennæ, which are expanded into a rounded club, or knob, at the tip. Yet, in other points, they vary to a very great extent, and, were it not for this distinguishing characteristic, would never be recognised as belonging to the same group of insects.

Families may be described as divisions of smaller size, many of them being often included in a group. They are composed of insects agreeing in their chief

characteristics, and generally exhibiting less variety of form than is the case in a group.

A genus is a smaller family, and sometimes consists of a single insect alone, in other cases of many hundreds. In a genus, as a rule, there is comparatively little diversity of form.

As regards the nomenclature of insects, every known species possesses two scientific names, just as is the case throughout the zoological and botanical kingdoms. The first is that of the genus, which is borne alike by all the insects included in it; the second that of the individual species. Besides these, in a full description, the names of the order, group, and family would be introduced. So, we might describe the well-known Purple Ground Beetle as follows-order, Coleoptera; group, Geodephaga; family, Carabidae; genus, Carabus; species, violaceus; while we should ordinarily speak of it merely as Carabus violaceus. Other members of the genus would be known as Carabus granulatus, C. auratus, and so on. The Red Admiral Butterfly, too, we should describe as-order, Lepidoptera; group, Rhopalocera (or Butterflies); family, Vanesside; genus, Pyrameis; species, Atalanta; speaking of it merely as Pyrameis Atalanta.

The Coleoptera, or beetles, are generally considered as being divided into twelve groups, each of which will be mentioned in turn.

The first, and one of the most important, is that of the Geodephaga, a word signifying 'earth-devourers,' i.e., predacious beetles living upon the land, as opposed to those inhabiting the water.

In this group are included many most interesting insects, some of which play no inconsiderable part in maintaining the balance of Nature.

For example, who would think that many of the enormous pine forests of the Continent, whence we obtain so large a share of our timber, owe their very existence to the labours of a single Geodephagous beetle? Yet, such is the fact, and, were it not for this insect, which is known as Calosoma sycophanta, hardly a pine-tree would now be left standing.

The beetle is a most gorgeous object, reminding one of tropical insects in the brilliancy of its colours. The thorax is of a deep violet black, with the borders brighter, as is the case in the Purple Ground Beetle, while the elytra, or wing-cases, are of a brilliant goldgreen shot with purple, the hues seeming to change with every movement of the insect.

In our own country this beetle is extremely rare, and the few specimens which have been met with have probably been accidentally introduced from abroad. Upon the Continent, however, it is plentiful enough, fortunately for mankind.

Its services, both as a larva and a perfect insect, consist in devouring the destructive caterpillars of various moths, more especially those of the Processionary (Cnethocampa processionea) and the Gipsy (Liparis dispar). But more destructive even than these, the grub of the Pine Saw-fly is more especially attacked by the Calosoma, which keeps down its numbers to a most wonderful extent. But for this, a single year would witness the destruction of large tracts of forest, for the pine-trees, once stripped of their leaves, cannot, like other trees, throw out fresh foliage, but speedily die.

So useful is the Calosoma, that it has even been introduced into infested districts where it did not previously occur, and with the very best results.

The well-known Tiger Beetles (Cicindelida) are included among the Geodephaga, and form the first family of the group. They may be seen on any sunny day throughout the summer, and are especially common on sandy banks, heaths, etc., dashing about in the hot sun like living gems, and taking to flight with the ease and rapidity of a blue-bottle. Both in the larval and perfect states these beetles, four species of which inhabit England, are extremely voracious, preying chiefly upon the smaller insects.

There is an extraordinary beetle in this group which

with the human skin it causes a slight burning sensation, and leaves a perceptible stain behind it. The beetle is chiefly found upon the banks of rivers, where fifteen or twenty specimens may sometimes be found beneath a single stone.

The greater number of the beetles of this group seek their prey only by night, retiring during the day to some place of concealment where they may be sheltered from their numerous enemies. They may often be found hiding beneath stones, dead leaves, etc., and in similar places.

has the singular property of possessing a mimic artillery with which to repel its foes. This is the Bombardier (Brachinus crepitans), which secretes a highly volatile fluid, a small quantity of which it can expel at will. When pursued by any of its numerous foes, the beetle ejects a small portion of this fluid, which passes into vapour as soon as it comes in contact with the air, causing at the same time a slight explosion, and effectually alarming its enemy. This discharge it can repeat twenty or thirty times in succession, the cloud of blue smoke bearing a remarkable resemblance to the fire of small artillery.

Should any of this volatile fluid come into contact

The next division is that of the Hydradephaga, or Water-devourers-i.e., predacious beetles which live chiefly beneath the surface of the water. Their structure is worthy of a detailed examination.

First, as regards their swimming capabilities. All these beetles swim by means of the hind-legs, which are very long, flattened, and closely fringed with long stiff bristles. These legs perform the functions of oars, and are formed in such a manner that, as they are brought forward for a second stroke, they turn sideways and present their edge to the water, thus cleaving through it, and offering no resistance. In fact, they are 'feathered,' just as are the oars of a boat,

only in the case of the insect the operation is entirely mechanical.

Although of the greatest service in the water, enabling their owner to travel at a considerable speed, these legs are of very little use upon dry land, and, indeed, seem rather to incommode the insect than otherwise. It proceeds by the most awkward and ungraceful waddle that can possibly be imagined, feeling, no doubt, much as does a skater when his rapid and easy evolutions are suddenly stopped by the breaking of a skate, and he is obliged to walk back upon the ice.

These water-beetles are possessed of broad and powerful wings, which enable them to pass from pond to pond at will. They usually perform their aerial journeys by night, and are accustomed, when they wish to return to their native element, to hover over a pond or stream, and, suddenly closing their wings, allow themselves to drop into the water, often from a considerable height. Sometimes mistaking the glass roof of a greenhouse for a pond, they fall upon the panes with a considerable shock, doubtless much to their astonish

ment.

Upon examining one of these insects it will be seen that, when the wings are packed away, a considerable space is left between the elytra and the body, the object of which may not at first be apparent. Its real use will shortly be seen.

Although the Hydradephaga pass a considerable portion of their existence beneath the water, they are not provided with gills, as are the fish, but are forced to breathe atmospheric air, just as are all other insects. For the purpose of renewing their supply, these insects. rise to the surface of the water every few minutes.

As, however, a single respiration would suffice for so short a time that the insects would be able to spend a few seconds only beneath the water, they are provided with the means of carrying down a supply of air with them, the space between the elytra and the body serving as a reservoir. Into this, the spiracles, or breathing holes open, and a water-beetle can thus remain submerged for a considerable space of time.

When the supply of air needs renewal, the insect floats head downwards at the surface of the water, the tips of the elytra just projecting, and the long hind-legs being spread out on either side like oars. The exhausted air is then expelled with a curious popping sound, and a fresh supply taken in. On a fine day, the water insects may be seen floating in numbers on the surface of any pond, the least footstep, however, being sufficient to alarm them and cause them to retreat to the depths below.

The shape of these beetles is admirably adapted to their subaquatic life, the form bearing a close resemblance to that of the fish, while the smooth and polished surface of the body affords but little resistance. to the water.

In some of the beetles of this class, and notably in the Great Water-beetle (Dyticus marginalis), the tarsi of the front legs of the male are modified in a very peculiar manner, being dilated into a broad pad. Upon examination with a magnifying-glass, this pad is seen to be furnished with a number of suckers, some thirty or forty in all, of various sizes, some of which are set upon stalks, while others proceed from the pad itself. As the air can be exhausted from beneath each of these suckers, the clinging power of the insect is very great, it being able to ascend the perpendicular sides of a glass jar without any apparent trouble. This

structure is found in the male alone, the tarsi of the female being perfectly simple.

The sexes of this insect can be easily distinguished by a single glance at the elytra, which in the female are deeply grooved for about two-thirds of their length, those of her partner being smooth. The insect is plentiful in ponds throughout the kingdom. A very similar insect is the Lesser Water-beetle (Acilius sulcatus).

The name of this beetle is a singularly appropriate one, the word Dyticus, from the Greek, signifying a diver, and being applied to the insect on account of its swimming capabilities, and the term marginalis referring to the yellow border of the thorax and elytra. Several species of the genus inhabit England, of which the above-named is by far the most abundant.

The larvæ of the various water-beetles are fully as predacious as the perfect insects. They are long grub-like creatures, provided with six legs, and an enormous pair of horny jaws, to aid in the capture and detention of the prey. These jaws are perforated throughout their length, somewhat after the manner of the poison-fangs of a serpent, and through these channels the juices of the prey are sucked into the mouth.

These larvæ proceed in the water in a curious sinuous manner, approaching their prey from beneath, and seizing it before their presence is detected.

The change to the pupal condition does not take place in the water, the full-grown larva leaving the pond, climbing the bank, and burying itself in the damp mud, forming for itself a round chamber or cocoon therein.

Then there are the curious little Whirligigs, or Whirlwigs (Gyrinus natator), which may be seen dashing about in numbers on the surface of any pond, their polished black bodies gleaming in the sunlight. The legs are formed in a very curious manner, the second and third pairs being so short as to be scarcely visible.

It must not be thought that all the beetles inhabiting the water are necessarily Hydradephaga, for such is not the case. A large number are included in the Palpicornia, or Hydrophilide, which are, as a rule, not predacious, or only so in a very slight degree. The legs are formed more for crawling than swimming, the insects spending their existence among the weeds and mud of the ponds instead of leading the active life of the true water-beetles. All these beetles may be known by the palpi, which are as long as, or even longer than the antennæ, which never possess more than nine joints.

One of the best known, although not the most abundant of these, is the Black Water-beetle (Hydrophilus piceus), which, with the exception of the Stag Beetle, is the largest of our British Coleoptera, averaging about an inch and two-thirds in total length. This beetle will be seen represented in all its stages in the illustration on the opposite page.

The insect is remarkable for the manner in which the eggs are laid, a silken cocoon being formed by the female, and fastened to the stem of some water-plant. Within this cocoon the eggs are deposited, being thus sheltered from harm until the young larvæ emerge, an event which takes place in about five or six weeks.

The Palpicornia are not all frequenters of the water, many of them, such as the various Cercyons, depending for existence upon the droppings of animals, in which they spend the greater portion of their life.

NEXT in order comes the Tiger, which is spread

over a considerable part of Asia.

The animal which is popularly called the "tiger" by African hunters is only a large leopard, and the "tiger" of American hunters is the jaguar. It is by no means

equally distributed, some parts of the country being absolutely infested by the animals, while in others they are seldom or never seen.

The tiger is fully equal both in size and strength to the lion, and certainly surpasses that animal in the ease and grace of its movements. Its colour is a bright, tawny yellow, with a number of dark brownishblack stripes, some of which are double, running round the body at right angles to the limbs. On the lower parts of the body the fur becomes nearly white, and the dark stripes melt almost imperceptibly into the general ground colour.

Occasionally a tiger is found whose fur is of a uniform greyish-white hue, the stripes being scarcely visible. This is usually known by the name of White Tiger, but is merely a variety of the common species.

It seems strange that so brightly-coloured an animal as is the Tiger should be so extremely inconspicuous among the underwood of its native jungles. Such, however, is the case, and a tiger at the distance of ten or fifteen yards would be perfectly invisible except to the most practised eye. For the dark stripes harmonise so perfectly with the dark shadows between the upright blades of the long grass, and the tawny yellow fur so strongly resembles the bright hues of the surrounding foliage, that, until it moved, even the most experienced hunter would probably be unaware of the presence of the animal.

Like the lion, the tiger seldom undertakes more active exertion when in pursuit of prey than is absolutely necessary for the attainment of his object. He seldom or never attempts open chase, but prefers to stalk his quarry, sometimes for miles, gradually creeping closer and closer, until he is able to effect his purpose by means of a single bound.

In the same way the dreaded man-eaters" will follow human beings, generally devoting their attention to women and children, who are not likely to carry

weapons.

The mortality from these animals is very great, for a tiger, when once it has tasted human blood, ever after thirsts for it, just as is the case with the lion. In some districts, even, a victim is carried off almost daily, the mingled apathy and superstition of the natives allowing the animal to carry on his depredations with impunity.

The spots most infested by tigers are those localities where the road passes through a small copse, or patch of jungle, and where water is in the immediate neighbourhood. Where water is scarce, in fact, the tiger is seldom found, as he requires to quench his thirst after every meal.

In such a retreat he lies in wait, always upon the opposite side of the road to that on which his lair is situated, until some unfortunate animal, or human being, happens to pass by. With a tremendous spring he bounds upon his victim, dashes him to the ground, and drags his body across into his lair without being obliged to turn round.

Should he happen to miss his aim, as does sometimes happen, he seldom or never repeats his attack, but seems bewildered, and mostly slinks away among the bushes. Should a number of people be together, he always selects the last of them, so that in tigerhunting the post of honour is, as in a retreat, in the

rear.

The natives divide tigers into three kinds, namely, the Hunting tigers, the Cattle-eaters, and the Man

eaters.

The first are the younger animals, which are strong and active enough to hunt prey for themselves. The natives do not try to destroy these animals, and find them rather beneficial than otherwise, because they keep down the antelope herds that make havoc in grain-fields.

The second are the older animals, which can no longer trust to the chase for food, but hang about villages for the purpose of pouncing upon any stray cattle that may come in their way.

No less than seven such tigers have been driven out of one cover, so that the destruction which they work can easily be imagined.

Their mode of attack is always the same. They do not knock down their prey with a blow from the paw, as is generally imagined, but seize it by the nape of the neck, and with both paws on the head, twist its neck.

A single tiger has been known to destroy annually. between sixty and seventy head of cattle, none costing less than five pounds, and many being worth double the money. These cattle-eaters are curiously fastidious. When they have killed an ox, they drag it to their feeding-place, and then open and clean the body as neatly as any butcher could do, always putting the offal at some distance from the meat.

Old tigers, who cannot even destroy cattle, are tolerably sure to become man-eaters. Fortunately for the natives, European huntsmen never allow a maneater to live. It is even necessary to destroy every cub of a man-eater, for if a tiger, no matter how young, has once tasted human flesh, it becomes at once a maneater.

The fur of such an animal is never worth anything in a pecuniary point of view, as it is almost always mangy, bald in patches, dingy in hue, and never exhibits the rich, warm colouring of the healthy fur.

So great is the terror of the natives at the mere presence of a man-eater, that they seem quite demoralized. They never venture out at night, and even by day will only dare to move in large bodies, all being heavily armed and accompanied by the beating of drums and the shouts of men, the firing of shots, and the glare of flaming torches.

A single man-eater has been known to kill a hun

dred human beings in a single year, and to put a stop to traffic in a triangular district measuring from thirty to forty miles on each side. Many villages were wholly deserted, and others in which the inhabitants remained, were surrounded with strong palisades.

The claws of the tiger form most terrible weapons, being sickle-shaped, and as sharp as a knife. As is the case in the lion, the claws seem to possess some poisonous influence apart from the actual wound, for, in many cases, even a slight scratch has been productive of lockjaw, followed rapidly by death. One hunter, of many years' experience, states that he has never known a patient to die from the effects of a wound caused by the tiger's claws without suffering from lockjaw previous to death.

Naturally, no pains are spared to exterminate so powerful and dangerous an animal, and traps of all kinds are constructed for his capture.

Some of these are most ingenious. A very common method of destruction is the spring bow, which is set as follows:

Two stout posts are planted in the ground by the side. of the tiger's path, and to these the bow is firmly fastened, the string being parallel with the path. The bow is then stretched, and kept in that position by means of a stick, which prevents the string from approaching the wood. At the end of the stick is placed a long wedge, to which is fastened a cord, which crosses the path of the animal. The arrow, generally poisoned, is then laid in its place.

Naturally, as soon as the tiger presses the cord with his breast, the wedge falls, the stick is drawn away, and the arrow discharged into his body, where the poison very shortly proves fatal.

Should a tiger have paid a visit to a farmyard, and carried off a horse or bullock, his track is followed up until the carcase of the slaughtered animal is discovered. Knowing that the tiger will shortly return for a second meal, the farmer cuts a few gashes in the flesh and introduces a quantity of arsenic. very long, the tiger makes his appearance, and swallows great lumps of the poisoned food, which in a short time puts an end to his existence.

Before

Farmers in this country are familiar with a method of catching rooks, when they attack the newly-planted grain, by twisting up a number of paper cones, placing a grain or two of corn at the bottom, and smearing the interior with bird-lime. These are placed in the furrows, with the pointed end downwards. The rook comes flapping along, sees the corn at the bottom of the cone, and immediately attempts to secure it. His head once in, however, he is unable to release it, the tenacious bird-lime fixing the cone over his head, and preventing him from seeing. After a short time he is exhausted by his struggles, and is then easily secured.

In much the same manner tigers are often captured.

A number of the broad leaves of the prauss-tree are secured, and thickly smeared with bird-lime. These are laid in the animal's path, the hunter concealing himself in the neighbourhood.

The tiger passes along, and treads upon one of the prepared leaves, which adheres to his foot. Not being able to remove it, he rubs his paw against his head, after the fashion of the cats, thereby transferring the sticky substance to his ears and eyes. By this time he has todden upon more leaves, which serve to still further incommode him, and he struggles to free himself from

the mysterious substance, rolling upon the ground in his efforts, until he has completely covered himself with the bird-lime. Guided by his voice and struggles, the hunters come up and despatch him without difficulty.

Sometimes a building resembling a huge mousetrap is constructed, and baited with a sheep or goat, which is placed in an inner chamber, so that it cannot be reached from the outside by the claws of the tiger; or a large bamboo cage is built, the hunter taking up his position inside, and spearing his foe through the bars as he ventures to attack.

Sometimes a large bamboo platform is erected near the haunts of the animal, on the summit of which the hunter takes up his station, firing at the creature the moment it appears. Even should the wound not prove instantaneously fatal, and the tiger attack him, he is in perfect safety, being above the reach of its claws, while the polished bamboo affords no foothold to his infuriated enemy, who is easily killed by a second shot.

When a hunter has been fortunate enough to kill a tiger, he always preserves the teeth and claws as tokens of his success, and the natives would not think of leaving the dead tiger without burning off its whiskers, as a kind of charm.

Besides these manifold traps, the tiger is also hunted in various ways, the most usual being by means of elephants. Upon these animals ride the hunters, who are seated in the 'howdah' (pronounced 'hoodâh'), a sort of open carriage firmly fastened upon the back of the elephant. A large number of beaters are pressed into the service, who endeavour, by means of shouting, blowing horns, beating drums, letting off fireworks, etc., to drive the tiger from its concealment.

In spite of the size and strength of the animals ridden by the hunters, this sport is not without danger, the tiger often facing his pursuers, leaping upon the elephant, and even reaching the howdah.

It is only by careful training that the elephants are induced to face the infuriated beast at all. First, they are taught to familiarize themselves with a stuffed skin, and to gore it with their tusks, and trample upon it. Next, a boy is placed inside the skin, in order to counterfeit the movements of the animal, and accustom the elephant to the sight of the skin in motion. Finally, a dead tiger is shown to the animal, instead of the stuffed skin.

Yet, with every precaution, and the most careful training, even the most courageous elephant will sometimes turn and run before an angry tiger, in spite of the exertions of the 'mahout,' or driver, who rides upon the neck of the creature.

One would naturally think that so destructive an animal would be almost universally sought after and destroyed. Yet in many parts of the country the tiger is absolutely protected, being considered as a sacred animal, and treated accordingly. Many of the native chiefs, too, protect it for hunting purposes, just as the fox is preserved in our own country.

The tiger is a good swimmer, and has even been known to board vessels lying at a considerable distance from the shore, and causing the greatest consternation among the crew.

The young of the tiger are two or three in number, and do not arrive at their full growth until three or four years have passed.

Owing to the colouring of the skin, to which allusion has been made, the tiger can with difficulty be discovered, even when its haunts are known, Hunters