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neighbourhood. Before the end of May all such trees should be barked, and as, by that time, the stems will be thickly beset with larvæ, the bark can be removed quite easily. In delaying the process of barking till May the logs are not only rendered unfit to serve as future breeding places, but, what is most important, they are utilised as lures or traps, to which a large proportion of the beetles in the neighbourhood are attracted, and in which they are subsequently destroyed. On no account, however, must barking be de. layed beyond the end of May. The bark removed should be deposited so that its inner surface, where the larvæ and chrysalids are found, is freely exposed to the sun and birds, and if this is attended to there is small chance of any of the young insects escaping. It is only when the bark is very thick that there is a likelihood of the immature insects completing their development in the bark after it is stripped off, and, in such a case, burning may be undertaken.
Small brushwood does not offer satisfactory breeding facilities for this insect, but it may serve the purpose for others, so that it is well to destroy it. Large branches, however, should be treated as recommended for stems. The Pine-beetle will also breed in the part of the stools above ground; and in the month of May the bark of stools should be pressed off by means of a spade, or other suitable tool, and, being generally thick, should be burned..
All Pines that die in the course of the summer should be felled and barked within two months.—(Board of Agriculture Leaflet, No. 91, The Pine-Beetle (Hylesinus piniperda). See also J. Clark, A Battle with Beetles, in Trans. Roy. Scot. Arbor. Socy., vol. xvi., part ii., 1900, pp. 274-276).
3. The Crutch Pine-Beetle (Hylesinus (Hylastes) palliatus) often occasions great damage along with H. piniperila in the north of Scotland. It is perhaps often overlooked, as it does not require freshly felled material for its breeding-place, but can make use of stems that have been felled for some considerable time. The beetle chiefly attacks Scots Pine, but also Spruce, Larch, and Silver Fir in Scotland in middle-aged woods; but both beetles and grubs damage the bark and cambium.
Appearance.—The beetle is only about f of an inch long, and somewhat broad for its length. The head and the edges of the wing-cases are black or brown-black, and the thorax and wing-cases are red-brown or brown-red. The thorax is broader than long, and is much narrowed in front. On examination with a magnifyingglass, it will be seen to be thickly covered with coarse punctures, and to have a smooth raised line running down the middle. The wing-covers exhibit rows of finely punctured longitudinal lines, and the spaces between these contain little tubercles and rows of fine hairs.
Life-history.—There are two generations in the year, the time from ovideposition to the issue of the new beetles taking about three months, but varying of course a little according to weather conditions. The cycle is sometimes continued much longer in the case of individuals still in the grub stage in late autumn, when they hibernate before pupating. Pairing and egg-laying take place in March and April. After boring into the bark of recently felled or older stems, a main-gallery is formed longitudinally. It begins with a boot-shaped or crutch-like bend (whence the beetle's name), extends for about 1} to over 2 inches, and is somewhat bent ; and while this is being formed, both the male and female beetles are to be found in it. The eggs are laid in little niches hollowed out along the sides of this gallery. On hatching out, the curled, yellowish, legless grubs, which have brown heads and biting jaws, begin to eat larval-galleries at right angles to the main-gallery, then deviate more or less irregularly or longitudinally, so that these galleries often cross and interlace. The pupal-chamber is formed either in the bark or in the sapwood. After the beetles emerge, the trees look as if riddled with small snipe-shot. The beetles issuing in July pair and
reproduce themselves at once, the eggs being laid in the stems already previously used as breeding-places. This second brood of beetles issues in October, and the beetles hibernate in bark-fissures, moss, &c., till pairing-time in the following March and April.
Prevention and Extermination consist in the use of decoy.stems from March till October, which should be examined and destroyed, along with the brood contained, at intervals of not more than six weeks from the time of preparing them. -(MacDougall, in Trans. Roy. Scot. Arbor. Socy., vol. xvi., part i., 1899, p. 153.)
4. The smaller Pine-Beetle (Hylesinus (Hylurgus) minor). —This beetle is occasionally found in the north of Scotland along with H. piniperda and H. palliatus, chiefly in Scots Pine, and occasionally also in Spruce, pole-woods and middle-aged crops. This beetle prefers to breed in sickly standing Pine-trees rather than in felled timber, because the thin-barked parts dry soon.
Appearance. It is to of an inch long, and is distinguishable by having uninterrupted the knob-like tubercles with brush-like tufts at the extremities of the wing-cases. It is more of a brown or red-brown colour than deep brown or black.
Life-history. Unlike H. piniperda, which forms vertical main-galleries, this beetle forms two horizontal galleries branching on each side of the bore-hole. These main-galleries are formed usually in the thin-barked upper parts of trees, and less frequently in thick-barked parts. Both the main- and the larval-galleries are therefore always partly, and the pupal - chambers entirely, formed in the sapwood.
Its life-history is otherwise much like that of the Pine-beetle. Its generation is sometimes single and sometimes double within the year. As a beetle it damages young shoots in the same way as the former, and is perhaps in so far the more dangerous of the two that it more frequently deposits its eggs in standing trees than in felled timber.
Prevention and Extermination consist in laying down decoy-stems and poles with thin smooth bark; but it is more difficult to operate against it thus than against H. pini perda and H. palliatus, because the thin-barked parts of trees and poles soon dry and then fail to attract H. minor. The decoy-stems must be barked early, before pupal-chambers are formed in the sapwood.
5. The black Pine-cambial Beetle (Hylesinus (Hylastes) ater) only does damage in the beetle-stage, when it attacks young 2- to 6-year-old plantations of Scots and other Pines. It is fairly common in Britain, but is not reckoned one of the very injurious insects.
Appearance.—This beetle is about į to } of an inch long, and black with redbrown feelers and feet. Thorax with parallel sides, elongated, densely and deeply punctured, and with a smooth ridge along the middle. Wing-cases with lines of deep punctures, wrinkled and with tubercles between the spaces.
Life-history. - The beetles, after hibernating in stumps or injured plants, fly from March to May, pair and lay their eggs in fresh stumps and roots of recently felled Pine-trees (chiefly Scots). The larvæ soon hatch out (in about 3 to 4 weeks) and begin to feed in the cambium, but without forming distinct well-defined galleries, and the whole cambial layer becomes a mass of confused borings filled with brownish bore - dust. In June the new brood of beetles issues and attacks young Pine plantations, gnawing the thin bark near the base of the stem and the upper part of the roots. At the same time they also
bore into the bark, and often tunnel all round the cambium. In consequence of this, plants attacked either sicken and cast their leaves or die, according as they may be only partially or completely girdled. The June brood of beetles may pair and produce a new generation in October, or they may hibernate in stumps and damaged plants, and reproduce themselves in the following spring.
Prevention and Extermination.—So far as practicable, grubbing of stumps and roots during May and June, after the eggs have been deposited, burying decoysticks in the ground as breeding-places, pulling up and burning sickly young plants, and delaying the replantation of recently cleared falls until the stumps and roots have become too dry to serve as breeding-places, are the best, and indeed the only, measures that can be adopted.
(3) True Bark-Beetles (Bostrichini, syn. Tomicini).
1. The small 3-toothed Spruce-bark Beetle (Bostrichus (Tomicus) chalcographus).—This beetle is only occasionally found in Britain, and usually on Spruce-trees, though also on Pines, Larch, and Silver Fir. It chiefly attacks the upper parts of the stem and the main branches, where the bark is thin ; but it is also found in pole-woods that are not thriving. As such poles and trees attacked soon grow sickly, they form favourable breeding-places for more dangerous insects.
Appearance. This is one of the smallest of bark-beetles. It is only about ily of an inch long, almost hairless, shining, and glossy. It is bright reddish-brown, with a dark thorax, and its dark - brown elytra are smooth towards the ends, dotted near their base with fine rows of punctures, and have on each side 3 dark tooth-like processes (hence the name 3-toothed). These are larger in the male than in the female.
Life-history.—The beetle usually flies from about the middle of April till the middle or end of May. It flies mostly during warm sunshine, and for egg-laying seeks windfall trees and recently-felled timber. But if not finding favourable breeding-places of this sort, it goes to the thick-barked parts of standing trees and lays its eggs in the upper parts of the stem. Its favourite breeding-places are then the sunny edges of woods and the warm side of trees standing next to falls and blank spaces—and in trying to exterminate this pest, it is there that decoy-stems should be laid as traps.
From the central pairing-chamber short mother-galleries radiate in 4 or 5 (and up to 7) star-like branches, and these form a characteristic of this species. The pairing-chamber and the stellate mother-galleries, as well as the larval-galleries, are bored partly in the bark and partly in the sapwood. The female lays from 30 to 50 eggs (and sometimes up to about 100, it is said) in small dents made close to each other and alternately on the right and left of the stellate main
Fortunately this is not a common insect in British woods, and its generation here is usually only simple and annual. On the Continent there are often two broods in the year, or else three generations require two years for development (the second generation in this case hibernating as larvæ). This and another similar beetle (B. typographus), also occasionally found in Britain, sometimes do enormous damage in Spruce-woods in Central Europe. Trees attacked by large numbers of these beetles soon stagnate and die through the larval-galleries interfering with the flow of the sap; but the beetles always emerge from the stems before they are quite dead, so that the felling of such trees does not help to exterminate the pest. On the Continent this beetle is almost always to be found here and there in Spruce-woods; but when circumstances specially favour its increase (after extensive windfall, or damage by snow, &c.), it may multiply to such an extent as to commit enormous destruction. It only exceptionally attacks other trees than Spruce,
galleries, the eggs being fixed in the dents with gluey substance. The larva hatch out about 14 days later, and bore sidewards from the main-gallery. The larval-galleries are at first at right angles to the latter, but gradually broaden and bite deeper into the cambium, until they are finally about 2 to 4 inches long. Then each gallery terminates in the pupal-chamber of the chrysalis. After pupating for about 8 days (or longer in bad weather), a bright yellow beetle emerges from the stem by a circular hole, but very soon darkens in colour. The development from egg to beetle takes about 8 weeks on the average (eggs, April, May ; larvæ, May, June ; pupæ, June, July ; beetles, July, August), or up to 12 weeks under unfavourable conditions.
The first brood of beetles flies from the middle of June till end of July. It immediately produces a new brood, which emerges as beetles in autumn. This second brood either pairs and reproduces a third generation within the year, or else the beetles hibernate and do not pair till the following spring. This beetle can therefore increase enormously under favourable circumstances.
Prevention and Extermination include the speedy removal of felled timber, the barking of stems that cannot be soon removed from the woods, and careful inspection of windfalls to see that they are not becoming breeding-places. Infested poles and trees should be felled and barked, and decoy-stems should be laid down in suitable places, and the bark afterwards peeled and burned.
2. The large 6-toothed Pine-bark Beetle (Bostrichus stenographus; Tomicus seedentatus).This is the largest of the bark-beetles; but it is not a very destructive species, and it is not common in Britain. It generally lays its eggs only in freshly felled timber, windfalls, and fuel-stacks; and it mostly attacks old thick-barked Scots Pine. Other Pines are less frequently used for ovideposition, and it is sometimes found on Spruce. When felled or stalked timber is wanting, however, it also attacks standing timber in old woods, and even pole-woods of twenty to thirty years of age.
Appearance.—The beetle is cylindrical, from į to } of an inch long, glossyblack or deep-brown with yellow hairs, and somewhat constricted at lower end. The antennæ and legs are yellowish-brown. The wing-cases have rows of deep grooves and punctures, and are pinched in where they curve downwards ; at their lower ends they have 6 tooth-like processes on each side (12 in all), of which the fourth is the longest.
Life-history.-In habits and life - history it much resembles the preceding species. It flies in April and May, and lays its eggs in vertical mother-galleries, which are up to 8 inches long or more, on each side of the entrance-hole and pairingchamber. They are mainly in the cambium, and hardly, if at all, penetrate the sapwood. The larvæ hatch out in June and July, feed for about 4 weeks, then pupate for about other 4 weeks, and emerge as beetles in August and September. Sometimes a new brood is at once reproduced, which also reaches the beetle-stage by autumn and hibernates under bark before pairing in April and May ; but if pairing has not taken place in August and September, the beetles hibernate till the following spring. The generation is in Scotland usually simple and annual, though there is often a double generation in the year in warm Continental localities.
Prevention and Extermination.—Barking timber attacked usually keeps this not very destructive beetle well in check.
3. The 2-toothed Pine-bark Beetle (Bostrichus bidens; Tomicus bidentatus).—This is a frequent pest in Conifer woods throughout Britain, and it is the commonest species of Bostrichus in our woodlands. It chiefly attacks Scots Pine, but is also found on other Pines, and occasionally also on Spruce and Larch. Its attacks are mainly confined to 10- or 12-year-old plantations, or to the thin-barked portions (the crowns and branches) of poles and trees. It may sometimes become a very injurious insect, doing extensive damage in plantations, and even interrupting the canopy of old Pine-woods.
Appearance.—The beetle is only about it of an inch long, and is black, glossy, and covered with fine hairs. The wing.cases are usually dark-brown, and have rows of fine punctures. In the male both wing-cases are broadly and flatly indented ; on the upper edge of each of these indentations there is a large, hooked, tooth-like process (hence the name bidens); but these indentations and tooth-like processes are absent in the female.
Life-history.—The beetles appear in May and June, and lay their eggs on the thin bark of young plantations, pole-woods, and living or dead branches of Pinetrees. The larvæ hatch out in June and July, feed for about 4 weeks, then pupate in July and August, and emerge as beetles in August and September. The main-galleries radiate in a star-shape, but differ from those of B. chalcographus by greater irregularity, by both the main- and the larval-galleries entering more or less into the sapwood, and by the pupal-chamber being mainly in the sapwood.
The first generation usually emerges in July, and proceeds to pair and produce a second generation, appearing in September. In warm dry seasons this can also produce a third generation, which hibernates as larvæ ; but this second generation of beetles usually hibernates till the following May or June.
Prevention and Extermination mainly consist in keeping the woods clean, in thinning and removing sickly poles, and in laying down traps of small thin-barked branches and twigs (such as may be cut from decoy-stems set for larger barkbeetles), and then burning them after egg-laying is finished in June. Seedlings or saplings attacked should be pulled up and burned, and poles infested should be felled and barked, and the bark burned.
4. The Larch Bark-Beetle (Bostrichus (Tomicus) laricis).—Next to Bostrichus bidens, this is the Bostrichus most often found in British Coniferwoods. This beetle is not chiefly found on Larch (as its scientific name would imply), but on Scots and other Pines; it also, however, attacks Spruce, and sometimes Larch and Silver Fir. It is found chiefly in poles, the upper parts of trees, and stacked fuel.
Appearance.—The beetle is to } inch long, broad and cylindrical, usually dark-brown (but sometimes light-brown), with scattered grey hairs, and rustybrown antennæ and legs. The wing-cases have close rows of punctures, terminate abruptly (almost at right angles), are circularly indented, and are toothed with from 3 to 6 processes on each side.
Life-history.— The beetle flies in April and May. The larvæ hatch out in May and June, pupate in June and July, and emerge as beetles in July and August. The July beetles pair and produce a second brood, the beetles of which emerge in October. This latter brood, as well as stragglers of the first brood, hibernate under the bark as beetles.
The mother-galleries are vertical but irregular, often twisting about and branching off into short supplementary galleries. The pairing-chamber is generally boot-shaped; and the female lays 30 to 40 eggs in one or two clusters at the end of a main-gallery often only about 1 to 2 inches long. The larvæ feed in common in family-galleries running irregular and confused in different directions ; hence the larval-galleries are not distinct as with most other bark-beetles.