CHAPTER XXI

INSECT ENEMIES OF TREES

Whether viewed from a commercial or sylvicultural point of view, the widespread damage caused to timber from insect attacks can scarcely be overrated. The depredations in various parts of our own country, particularly in young plantations, are bad enough, but when compared with those of Europe and America they appear insignificant. In France and Germany whole woods have been wiped out by insect pests, while the Government of Bavaria were mulcted in something like £100,000 by the destruction of its spruce forests. The United States fares no better, for we find that over a period of ten years the amount of timber killed and reduced in value was calculated at fully £10,000,000. The coffee plantations of Ceylon suffered much from the attacks of a fungus, and we could go on multiplying cases. In our own country the ravages of the pine beetle and of the larch disease have caused incalculable damage; indeed, in the latter case there is hardly a plantation of larch where the presence of the fell disease cannot be distinctly traced, while the pine beetle has ruined whole plantations both in England and Scotland. Though the adult bark and wood-boring beetles do a great amount of damage, yet that inflicted by the caterpillar or grub from the egg is greater still, and in the case of fungi we have a typical example of their destructive properties in the case of the well-known larch disease.

The =Pine Beetle= (_Myelophilus {Hylurgus_} _piniperda_) is a dreaded enemy to not a few species of Pinus, but particularly _P. sylvestris_, _P. laricio_, _P. austriaca_ and _P. Strobus_. The injury done by this beetle consists in its destruction of the leading shoots of the tree it attacks. It enters by boring a hole into the side of the shoot until it reaches the pith, after which its course is directed upwards, and an exit made at the terminal bud. This tunnelling of the shoot so weakens it that frequently during stormy weather it is broken across at the point where the beetle entered. Not only are unhealthy trees attacked by the pine beetle, but young and robust-growing specimens frequently fall a prey to its insidious depredations.

June, July and August are the months when it is most commonly found.

The only remedy is to collect and burn the affected shoots—work that requires to be done with the utmost care to prevent the escape of the wary insect. Burning all brushwood in plantations is a great preventive.

The =Pine Weevil= (_Curculio_ {_Hylobius_} _Abietis_) is another destructive insect, which differs from the former in waging its attacks against the buds of the leaders and branches, as also by eating patches of the bark here and there on the stems and branches. The various species of Abies suffer most, but the pines are occasionally attacked as well. It is always most destructive in young plantations growing on the margins of old woods, and equally bad amongst trees that have been planted on the site of a former pine plantation.

The beetle is about half an inch long, and nearly black. One remedy, probably the best, is to place fresh pieces of pine bark on the ground, beneath the infested trees. By shaking the trees and examining the traps the following morning, many may be destroyed.

=Bostrichus typographus= is another pest of our woodlands, and may frequently be seen, like fine white wool, spreading over the stem and branches of the silver and other firs. It spreads with terrible rapidity, first appearing in small patches here and there on the bole, and particularly on the under sides of the branches. The tree infested soon becomes unhealthy, and frequently dies off prematurely. Trees growing in low-lying, heavy ground would seem to fall a first prey to this insect.

=Bostrichus laricis= is nearly allied to the former, but its devastations, which are, however, not very deadly, are principally confined to the larch. It is usually known as the “larch blight.”

The =Pine Shoot Moths= (_Retinia buoliana_ and _R. turionella_) would seem to be more numerous in this country than is generally supposed. Quite lately I visited a large plantation of young Scotch fir, the terminal buds of which were greatly injured by the caterpillars of this elaborately-coloured moth. The moth lays its eggs at the base of the buds, and into these the caterpillars enter by hollowing out the centre, thus destroying their vitality and causing them to take on a withered appearance and to feel soft and empty to the touch. Trees infested by this insect resemble greatly in their stunted shoots and exudation of resin such as have become a prey to the Pine beetle (_Myelophilus piniperda_), only in the latter case it is the fresh young shoot and not the bud that is attacked. The _Retinia_ would seem, from all my notes and observations, to be most abundant in what might be termed neglected fir plantations, that is, where the trees have suffered from overcrowding, or from unfavourable conditions as to soil, etc., and particularly when the wood is composed entirely of one species. There is no method of dealing with large infested areas, for the attacked trees have repeatedly been cut over and removed without any seeming diminution in the numbers of the insect. One experiment with a small infested corner has been rewarded with good results, viz. the lighting of a fire to windward, and causing the smoke of coal tar to pass over the infected area. This might be worth trying in the case of fruit trees infested by particular insects.

The =Larch Miner= (_Coleophora laricella_).—Few, other than those specially interested in tree diseases, have the remotest idea that the yellow, withered appearance of many of our English larch plantations is due to the larvæ of the above tiny moth. It usually attacks young trees, say, from five to twenty years old, and although it may not kill them out, yet the repeated onslaughts year after year tend to keep the trees in an unhealthy condition, and so render them liable to other and more deadly diseases.

Unfortunately the attacks of the larch miner are by no means confined, as is usually supposed, to trees growing under unfavourable conditions, for I have this season noticed in an unusually healthy, fast-growing plantation in Sussex that almost every tree was more or less affected. Certainly in another large extent of larch in Gloucestershire which I examined lately, where nine-tenths of the trees were being ruined by the _Peziza_, the larch miner was very abundant; but, I think, that young trees, whatever may be their state of health, suffer alike, although where hard-wooded trees form a portion of the crop the larch certainly suffers less than when grown in pure woods. The moth lays its eggs at the end of June on the needles of the larch; the caterpillar mining into and feeding upon the interior of the needle causes it to turn faded and yellow. It lives in the tube thus formed during the winter, changing to a pupa, and ultimately to a moth. It is a most difficult matter in the case of this insect, as, indeed, of all others that are fairly abundant, to suggest a remedy, and I have looked over and examined larch plantations that are differently situated in many respects to find out under what condition the attacks are most persistent, but with little or no success—healthy and unhealthy, native or Tyrolese, faring alike when grown as a pure crop.

Where the larches are intermixed with hard-wooded trees—sycamore, oak and beech—the attacks are certainly less frequent, as I have noticed in a number of cases. Trees growing at high altitudes do not seem to suffer less than those only a few feet above sea-level, and this point I have paid particular attention to.

Whether the wounds caused by this insect will serve as a nidus for the spores of _Peziza Willkommii_ has yet to be determined, but special importance should be attached to all larch-feeding insects, and their depredations minimized to as great an extent as possible.

The =Pine Sawfly= (_Lophyrus Pini_).—Fortunately, this insect is not abundant in the British Isles, though on the Continent the damage it does in the pine forests is by no means inconsiderable. The insect may readily be recognized by its wide, flattish body, and usually dark appearance. Having attained to full size in the trees, they form cocoons among the foliage or on the stems, and remain in this condition until the following spring, when, in April or May, the perfect insects make their appearance. The male is considerably smaller than the female, while the full-grown caterpillar, which is of a greenish-yellow colour, with a row of black spots on either side, is about an inch long. The remedial measures are not at all easy, especially when a large number of trees are attacked, but single specimens may be entirely cleared by shaking the caterpillars into a sheet placed beneath the tree.

[Illustration: (_a_) WILLOW BEETLE (_Phyllodecta vulgatissima_), AND (_b_) ITS LARVA.]

The =Larch Aphis= (_Adelgis laricis_) and =Giant Sirex= (_Sirex gigas_) are both, more or less, harmful to the larch. The latter is a formidable and splendid insect, which is, however, not very abundant in this country.

Generally felled trees, or such as are somewhat sickly, are chosen by the female in which to lay her eggs. These are deposited beneath the bark by means of the powerful ovipositor, and in course of time the whitish cylindrical maggots make an appearance, and with their strong jaws form large borings in the affected tree.

Cutting down and burning infested trees is the only practical remedy.

The =Willow Beetle= (_Phyllodecta vulgatissima_) causes considerable damage to osier plantations, and would appear to be greatly on the increase of late years. Much damage has been done to osier holts in various parts of the country, and in northern Ireland the ravages of this beetle were particularly noticeable during the past five years. The insect, which is metallic green or blue in colour, passes the winter in the adult state, at which time it may be found amongst refuse of the osier beds, such as the heaps of bark, and also at the base of old stools and beneath stones or other shelter. The larvæ have a tough yellowish cuticle with conspicuous brown bristles, the head and prothorax being black and hard. The eggs are laid on the undersides of the leaves in spring, and when the larvæ are hatched they feed on the leaves, eating holes quite through to the upper surface. Burning all rubbish in the osier beds is to be recommended, and spraying with Paris green or lead arsenate has been found useful.

The =Larch Sawfly= (_Nematus Erichsonii_).—This is a species of sawfly the larvæ of which bear considerable resemblance to those of the caterpillar of the pine sawfly, and also to that of the better known gooseberry caterpillar. The larvæ are about three-quarters of an inch long, and possess twenty feet. From July to August they feed on the leaves of the larch, and a plantation that has been attacked presents a partially leafless condition with quantities of the brown cylindrical cocoon cases lying amongst the grass beneath the trees. There have been several notable instances in which larch plantations have suffered severely from the attacks of this insect, and in northern England, particularly Cumberland, whole areas of plantation have been attacked. Burning all brushwood and grass beneath the trees in infected plantations is probably the best means of lessening the numbers of this dread insect in our larch plantations.

The =Spruce Gall Aphis= (_Chermes abietis_).—This is a common insect, and one that renders many fine young spruce trees very unsightly by reason of the cone-like excrescences that are formed by the action of the insect on the shoots of the infested specimen. The formation of this excrescence is brought about by the female aphis piercing with her beak, or sucker, one of the buds, and drawing off the sap, the consequence being an unusual growth at that part.

When the young larvæ appear, they also, by piercing the gall, extract the juices, and the gall enlarging soon causes the larvæ to become embedded at the bases of the leaves, which, by this time, have become curiously malformed. The insects are scarcely one-tenth of an inch long.

[Illustration: ELM TREE DESTROYER]

A. Entrance of Parent Tube. B. Insect in Tube. C. An imperfect Tube arrested from want of nourishment. D. Scolytus Destructor. Natural size. E. Lateral Tubes with Larvæ, some changing to the Pupa state.

The only remedy is to collect the cone-like excrescences and have them destroyed, except in the case of badly infested trees, which should be cut down and burned.

The =Elm Tree Destroyer= (_Scolytus destructor_) is about one-fifth of an inch long, stout and cylindrical, and usually confines its depredations to the elm.

In the beginning of June this beetle bores into the inner bark, where it forms galleries, along the margins of which are laid the eggs. Cutting down and burning badly-attacked trees is the best remedy, but promoting exuberant health of the infested specimens by means of enriching the soil has been attended with promising results.

The =Goat Moth= (_Cossus ligniperda_) is most frequently found on the willow, oak, lime and other trees. Being not only one of our largest native moths, but also one of the most destructive, its ravages are much dreaded, the holes or tunnels made by the moth being of large size—large enough to admit the little finger. Filling up the tunnels with a mixture of soot, lime and cow manure is an excellent remedy.

The =Lackey Moth= (_Clisiocampa neustria_), so called from the gay colours of the caterpillar, is another destructive woodland pest, eating wholesale the leaves of the oak, elm, beech, poplar and most fruit trees.

In April and May the caterpillars are hatched, when the leaves are just unfolding. They form a nest or web of silken hairs, generally amongst the smaller branches, in which they live during the day, sallying forth in the evening to feed on the tender foliage. Being very plentiful, they are usually difficult to deal with, but hand-picking and destroying the cocoons are the only practicable methods of meeting the evil.

The =Winter Moth= (_Cheimatobia brumata_) and the =Lime Looper Moth= (_Hybernia defolaria_).—The caterpillars of both these moths are very destructive to the leaves of elms, limes and willows, but particularly to the buds of the apple tree.

When full grown they descend to the ground, where they cover themselves and become chrysalides, from which the moths appear from October to December.

Being almost wingless, it is by no means difficult to prevent their ascending the trees by painting a band of any sticky substance around the stems of the trees that it is expected they might attempt to crawl up.

[Illustration: A. Larva of the Cossus Ligniperda, three years old, ready to change into the Chrysalis state.]

[Illustration:

A. Cossus Moth. B. Chrysalis from which the perfect Insect has escaped. C. Cluster of Eggs. D. Magnified Ovum.

THE GOAT MOTH]

The =Red Spider= (_Tetranychus_).—In hot and dry summers trees suffer much from this member of the mite family. Limes and poplars, as also many other trees, are greatly injured, the foliage turning to a russety brown colour, and falling off long before the usual time. There are several remedies, such as fumigating and spraying with a solution of soft soap, but none of these are applicable to a plantation of trees, or even a single specimen of large size.

The =Thorn Fly= (_Aphis Cratægi_) attacks whole hedges or brakes of Quick, especially those in the nursery border; as a rule, the younger and more healthy plants first fall a prey to its depredations.

Sponging with tobacco water, or almost any of the prescribed solutions will rapidly exterminate the fly; but such work is laborious when a large brake or long hedge of the thorn has to be gone over.

The =Cockchafer= (_Melolontha vulgaris_) is usually pretty abundant, and does most damage by eating the leaves of the sycamore, beech, oak, cherry and many other trees. It will also eat the roots of most young trees, but those of pine in particular.

The insect is about 1¼ in. long, and of a chestnut-brown colour on the upper part of the body, while the head and some other parts of the body are of a bronzy green, and thickly covered with yellowish-white hairs.

In April and May the eggs are laid in a hole in the ground about 5 in. deep, and the grubs are hatched in July. They are of a dirty-white colour and much wrinkled. In this state, however, they do but little harm; but, after having changed their skins and remained in a torpid state during winter, come to the surface in spring and eat the roots of almost any plant that comes in their way. They again burrow deeper at the approach of winter, coming to the surface again in spring, and, when full grown, are about 1½ in. long, and almost ½ in. in diameter. The perfect insects do not live more than about twelve days, and are easily known by their heavy, awkward flight towards the evening.

The =Laburnum Moth= (_Cemiostoma laburnella_) is fairly abundant—in England, at least; and, in some instances, every leaf of a tree has been eaten almost wholesale by the caterpillars of this pretty moth. The insect is about one-eighth of an inch in length, and three-tenths of an inch across the fully expanded wing. It is of a silvery-white colour.

The greenish-grey caterpillars are about ¼ in. long.

By burning the attacked leaves great numbers of the caterpillars may be destroyed, while, by shaking the trees in May and August, the moths will fly out, and may be caught in a butterfly net.

[Illustration: WOOD LEOPARD MOTH

(_Zeuzera æsculi_)

(Very destructive to trees, particularly around London)]

=Wood Leopard Moth= (_Zeuzera æsculi_).—The caterpillar of this beautiful moth is very destructive to the beech, ash, birch, elm, walnut, privet, etc., which it bores into, eating and living on the wood. Usually young trees or the branches of old specimens are attacked, and the tunnelling is confined in the former either to the pithy centre or the soft wood near the bark. The moths appear about mid-July, and the female, by piercing the bark with her powerful ovipositors, deposits her eggs, one in each hole. Three years are required for the caterpillar to arrive at maturity when it is nearly 2 in. long. Both in form and colour the leopard moth is particularly elegant, the head and thorax being covered with a thick white pile, the body with a black down, fringed with white at each joint. The wings are white with yellowish-brown veins, a row of rounded bluish spots running between every two.

By stuffing a piece of tow in gas tar, or placing cyanide of potassium in the hole and closing the aperture, the caterpillar may be overpowered and destroyed.

A bent wire has often been successfully used in dislodging the caterpillar.

The =Holly Fly= (_Phytomyza aquifolia_).—The foliage of the holly is frequently very much disfigured by the grubs of the holly fly, which burrow beneath the upper skin of the leaves, feeding on the internal substance. This imparts a blistered and discoloured appearance, which, in the case of ornamental varieties, is anything but desirable. Probably no great damage to the infested trees is brought about, but the wholesale destruction of the leaves, as is often the case, cannot but weaken the plant.

In May and June the flies make their appearance, and lay their eggs beneath the upper skin of the leaf, from which the grubs, about one-fifth of an inch long, are hatched. These work their way beneath the skin of the leaves, forming small tracks of a more or less circular shape, thus causing the large and unsightly blisters. They quit the leaves about March, by making small holes in the skin of the leaf, and afterwards become chrysalides. The fly is small and inconspicuous.

Picking off and destroying affected leaves, or crushing the grub by pinching the blisters are the only ways of lessening the attacks.

The =Oak Leaf Roller Moth= (_Tortrix viridana_).—The widespread destruction caused to oak-woods in almost every part of the country by the caterpillars of this little moth would seem to be on the increase from year to year. But it is not the oak alone that suffers, for numbers of the hornbeam and beech are in an equally pitiable condition. Having closely watched this insect for several years, mainly with the view of striving to keep it in check or devise some means of destruction, I have come to the conclusion that a few individual trees may, at considerable expense, be rid of the pest, but in the case of whole woodlands artificial treatment is quite out of the question. Many observers are under the impression that the caterpillar is most abundant where the trees grow closest together, and when we consider that both wind and rain destroy numbers of these, the fact of isolated trees, which, consequently, are most exposed to storms, being comparatively free from attack is not to be wondered at. So far as we know at present, the only way to diminish in any appreciable degree the numbers of this insect is by encouraging as much as possible its enemies.

The rook, jackdaw, starling, thrush and sparrow help immensely in destroying the caterpillars, and the occupants of a rookery will frequently in a few hours clear the pest from the trees over a considerable area of woodland. The same has been noted with regard to the starling, and I have frequently seen the trees over an infested area almost black with this particular bird when in the act of feeding on the caterpillars.

In support of this recommendation it may be stated that insects are far less numerous in the forests of St. Germain, Senart and Fontainebleau than in the Bois de Boulogne, where, of course, small birds are scarcer.

Sometimes with the oak leaf roller moth its excessive number proves the means of its extinction, the foliage being devoured before the caterpillars are fully fed; while, as is usual at the season of attack, parasitic flies and ichneumons destroy them wholesale, and a box of caterpillars sent to me the other day revealed the fact that each one had succumbed to the attacks of one of these enemies.

The life history of this moth is full of interest, and the curious manner in which it rolls up the leaves is well worthy of study.

The =Felted Beech Coccus= (_Cryptococcus Fagi_).—Judging from the numerous specimens of the beech coccus that are being forwarded to me for identification, and the inquiries as to how this insect pest may be dealt with, its presence in almost every part of the country is indicated. It was only in 1862 that Dr. Balfour reported the presence of this coccus in Scotland, and I remember well how the beautiful beech hedges on the Penicuik Estate, Mid-Lothian, were ravaged by the insect in 1875. In Germany, however, the beech coccus was noticed as early as 1849. It is probable that the beech coccus also extends to the Weymouth pine, as at Keston, Lord Derby’s estate in Kent, several of these trees were badly affected with an insect that appeared to me identical with this pest, and other instances of the Weymouth pine being similarly attacked have been recorded. Since the appearance of the insect in Scotland it has spread southwards rapidly, but it is only of late years that its ravages have been felt severely, and that owners of woodlands have been driven to do everything in their power to combat its injurious effects. I think I have nowhere seen the insect so abundant as on the Burnham beeches, which I visited in company with several members of the Royal Horticultural Society at the request of the Lord Mayor and the Corporation of the City of London. Here, speaking broadly, all the trees are affected in a greater or less degree, independent altogether of the age or health of the trees.

Amongst the beautiful beech woods of Hertfordshire, where the timber produced commands a higher price than that from any other station in Britain excepting the Chiltern Hills, the trees are suffering severely. After a careful inspection of many beech woods, I am at a loss to account for the spread of this insect. Usually, in the case of injurious forest insects, the presence of dead and dying wood and the general health of the plantations have much to do with the attack, but this would not appear to be the cause in the case of the beech coccus. Even old and diseased trees do not appear to suffer more than the young and healthy specimens, and at Burnham some of the youngest and fastest growing specimens were by far the worst affected, appearing in parts as if coated with drifted snow. Neither would soil appear to have anything to do with the spread of the insect, as on chalky, sandy and loamy soils, as well as on shale rock, the trees are all more or less affected. I cannot say that unhealthy trees are more liable to be attacked than vigorous ones, for I have observed diseased trees to be sometimes quite free from the coccus, whilst healthy specimens in the immediate neighbourhood were badly infested. This was particularly noticeable on some park trees on two estates that I visited lately; in each instance the majestic boles rose to a height of fully 90 ft. and contained about 100 cubic ft. of wood. At one time I had an idea that beech trees when grown too thickly were most liable to be attacked, but more extensive observations have disproved the hypothesis. By some it has been suggested that the drainage of ground on which the beech is growing will facilitate the spread of the insect by bringing about an unhealthy state of the trees. To some extent this has been noticed at Burnham, and particularly in Gloucestershire, where a lake had been formed contiguous to a beech plantation. In another instance that came under my notice the burrowing of rabbits to an unusual extent was blamed for the appearance of the insect and the gradual death of the trees, the soil in this case being sand and gravel. It is a strange fact, too, that a badly infested tree may be standing amongst others that are perfectly free from the attack. Under a magnifying glass the insect appears of a yellowish colour, irregularly globular in shape, and almost transparent. It is thickly covered over by a secretion from the body, which looks like fine waxen-white threads or cotton wool, which effectually screens the insect from observation. With its proboscis it sucks up the juices, which are readily reached through the thin, smooth bark. When badly attacked, the foliage becomes meagre and has a burnt appearance, then the tips of the branches, and finally whole branches die off. Afterwards the bark becomes dry and cracks, usually longitudinally, falling off in flakes with the death of the tree. The timber of trees that have been killed by the coccus is dry, short-grained, and by no means comparable with that of healthy specimens. From whatever cause, the presence of the insect in our plantations is much to be deplored, and already many fine old trees in different parts of the country have succumbed to the attack. It is a curious fact that certain trees fall victims to the attack of this insect very rapidly, often in the short space of two years, while others of equal age and vigour, and, as far as can be seen, similarly situated, live for many years. Fully grown trees are, in my opinion, more liable to be killed quickly than younger specimens.

As regards remedies, these can only conveniently be applied to single specimens and are scarcely practicable on a large scale. That success has, however, attended the application of certain remedies I am quite convinced, for several valuable ornamental trees on a lawn in Buckinghamshire that were badly affected by the pest are now, twelve months after being treated, quite free from the insect, and do not appear to have suffered in consequence. In this case the remedy was simple, and consisted merely in scrubbing the tree stems where affected with a stiff brush dipped in an emulsion of soft soap, this being rubbed well into all crevices of the bark. Only one application was given, but as the trees were nearly 100 ft. high with many large limbs, which also showed the presence of the coccus, the work took a considerable time. However, the results well repaid the expense of labour. Another excellent remedy is to mix together equal portions of paraffin and soft soap, and when required for use add twenty times their bulk of hot water, stirring all well together. This may be applied either with a scrubbing brush or syringed on to the affected parts. Other measures of a more drastic nature have been found to be beneficial, but those given are probably the simplest and best. Three or four handfuls of lime to a bucket of water is an excellent application, the only drawback being the unpleasant colour imparted to the trees. This is a simple remedy, and may be applied with a painter’s or scrubbing brush. It has saved many trees on an estate near London.

=Wireworms.=—These occasionally do a great deal of damage in beds of seedling trees, particularly conifers, and in some instances they attack and destroy the seeds before germination. In the case of young conifers they are gnawed completely through just above or at the ground level, the beds in many instances being strewn with the cut-over plants. _Abies nobilis_ and _A. Nordmanniana_ suffer to a great extent, and I have frequently been at my wit’s end to put a stop to the repeated depredations. In the case of a newly-formed nursery or freshly-made-up seed-beds the attack of the wireworm is always most pronounced. In the case of fresh nursery ground, paring off and burning a couple of inches of the top soil in the autumn has been attended with excellent results, as has also dressing the ground with gas lime. When seedlings are attacked, hand-picking, with the use of sliced carrots, mangold or potatoes, varied with pieces of oilcake as a bait, are to be recommended. Dressing the seeds with red lead is very advantageous to prevent birds and mice from attacking freshly-sown quantities. Injury from wireworm is not likely to cause any serious consequences after the first year’s growth of the plants, especially if the ground has been kept clean and free from weeds during the egg-laying season in June.

[Illustration: WITCH’S BROOM ON THE WILLOW (SUMMER APPEARANCE)]

The above are only a few of the many insects that injure our forest trees; but those treated of are the most familiar to the forester, and those whose attacks he has most frequently to wage war against. Willow trees all over London are suffering severely from attacks of a mite insect. It is known as the “Witch’s Broom” on the Willow (_Eriophyes triradiatus_).

Remedial measures are frequently of little avail, more particularly when a whole wood or plantation is attacked; but with single specimens the numbers may readily be lessened by the methods suggested.

[Illustration: WITCH’S BROOM ON THE WILLOW (WINTER ASPECT)]

Keeping the woodlands free of dead and dying trees and branches is a preventive of insect attacks that should never be neglected.

As showing the injury that can be inflicted on our forest trees by some of these insect pests, the following cases may be mentioned:—

During fifteen years (between 1853-68) the spruce in East Prussia, Poland and Russia was killed over an area of 7,000 square German miles; while in the Bavarian forests, the loss to the Revenue in one year was £40,000.

In both cases the destructive insect _Liparis monacha_ was the cause of injury.