« ForrigeFortsett »
the following spring they reascend and feed for a short time. In June, three years after hatching out from the egg, they burrow deep into the soil and pupate in an oval hole with smooth hard walls. After from 4 to 8 weeks of pupal rest the beetle comes out soft and white, but gradually hardens and deepens in colour. Without coming to the surface it hibernates below ground, and does not emerge till the following spring (May), when it issues from a hole such as is made with the point of a walking-stick.
This beetle requires in Britain four years for its normal generation (though in
warm southern countries the generation takes three years only). They may therefore be expected to swarm at regular intervals of every four years, although a few stragglers may usually be seen in the intervening years.
Prevention and Extermination.—So far as practicable, the female beetles should not be given any favourable opportunity of laying their eggs on large blank spaces with loose soil in years when many beetles may be expected. For example, notching is then preferable to pit-planting on suitable soil. In localities where chafers are known to abound nurseries should not be formed near pastures or young Oak crops, as the beetles may fly from these to lay their eggs. Nurseries,
See also Mr F. Moon's Account of a Chafer Infestation, in the Trans. Roy. Scot. Arbor. Socy., vol. xviii., pp. 201-207, and a Note on the Cockchafer, in Prof. MacDougall's Report, ibid., pp. 208-210; also Board of Agriculture Leaflet No, 25.
whether temporary or permanent, should be surrounded by a trench preventing the entry of grubs. The best protection, however, is to hang up nesting-boxes for starlings all round the nursery, as these most useful insectivorous birds take kindly to this assistance, and well repay the cost and trouble taken to increase their number.
But besides the starling, there are many other animals which prey on cockchafers and white grubs. Pigs, hedgehog, badger, fox, mole, &c., devour grubs in the ground, and bats, owls, crows, rooks, jackdaws, gulls, goat-suckers, stannelhawks, sparrows, &c., also destroy many of them when swarming and laying eggs.
These natural remedies fail, however, to check the periodic chafer-years. One of the best ways of trying to exterminate the pest is to collect the beetles from the lower branches of trees along the green rides and open spaces, and from Oakcoppices. The beetles can easily, and especially in the early morning, be shaken down from young poles (lightly, else they hold on firm), picked up from the ground, and afterwards killed by pouring boiling water over them, or by dipping the sacks containing them into hot water, when the dead beetles are eaten greedily by pigs and poultry. But to be effective such collection must take place as soon as the beetles appear (to be in advance of the egg-laying), and it should be made simultaneously throughout the whole neighbourhood infested. Another way of killing them when in large numbers is to put them into a hermetically sealed wooden box with a small quantity of sulphide of carbon, and keep them there for some hours. (This will also kill book-worms, if infested books be similarly treated for thirty-six hours.) Farmers are quite as much concerned as foresters in annihilating this pest, and should therefore co-operate and collect all chafers found in their pasture-lands and orchards, or on field and hedgerow trees.
To exterminate the grubs is difficult, and can only be managed in nurseries, where their presence is soon shown by the withering of seedlings attacked. The grub can then usually be found on one of the nearest plants. It is only by digging and hunting each grub that the beds can be protected. The grubs can also be trapped with sods of turf, about 8 to 12 inches broad and 6 to 8 inches thick, laid, grassy side downwards, on the ground; or heaps of turf humus, dung, &c., may also be employed. The grubs collect under these, and can then be gathered and destroyed. Or potatoes may be placed below the surface of the ground, and examined daily.
Where soil-preparation is necessary before sowing or planting, the grubs should be collected while the soil is being broken up, and here they can often be trapped in sods of turf laid grassy side downwards. The herding of pigs is then also of use.
But in young plantations swine cannot be employed, as the grubs lie too deep in the ground to be reached without a good deal of snouting.
2 and 3. Equally abundant and just as destructive as the Cockchafer are the two smaller species, the Summer-Chafer (Rhizotrogus solstitialis) and the Garden-Chafer or Bracken-clock (Phyllopertha horticola), and all three have increased very much in Britain during the last ten years. Though they feed on almost any roots, those of grass and seedling trees are most liable to attack, young Oak and Pine often suffering severely.— These two smaller beetles are easy to distinguish from the larger Cockchafer, but the grubs are very similar when young, and difficult to identify, though they are smaller when full-grown. The habits of the grubs are very similar to those of the Cockchafer.
Appearance and Life-history. The Summer-Chafer is about of an inch long, reddish-brown, and slightly hairy.—The Garden-Chafer varies from about to } an inch long. The front part of the body is greenish with a metallic sheen, and the wing-cases are reddish-brown. The male beetle is very hairy.—These both appear in June and July, or about a month later than the Cockchafer; and this is a point of importance with regard to collecting and destroying the beetles. The
larval or grub stage varies from one to two years for the Summer-Chafer, and is only one year for the Garden-Chafer, while it is three years for the Cockchafer.
Prevention and Extermination are as for the common cockchafer. 4. Two other species of the same genus which only do slight damage are :
The Horse-Chestnut Cockchafer (Melolontha hippocastani), which much resembles the Cockchafer in appearance, habits, and life-history, but occurs less frequently, and can easily be distinguished by its red thorax and its smaller size. It especially attacks the Horse-Chestnut.
The Fuller or Garden Beetle (Polyphylla fullo), the largest of the Cockchafer genus, which is found here and there in sandy tracts, and is easily recognisable by its brown wing.cases with white marbling.
D. Longicorn Beetles (Cerambycidce).
The long-horned family of beetles is chiefly characterised by the antennæ being often several times as long as the body (hence the name). Some are large, and generally they have elongated strongly-built bodies and long legs. They are not very destructive in Britain, and chiefly attack Poplars and Willows. The beetles live on leaves and flowers, and are practically harmless; but the larvæ live in the wood, and are therefore destructive.
Appearance. The beetles are long, have a round thorax (often with prickles at the sides), and somewhat flattened wing-cases considerably wider than the thorax at the base and tapering towards the apex. The abdomen has five segments. The long antennæ have usually eleven or more joints (the second always being the shortest), and taper in size towards the end. Legs long and slender, with 4-jointed tarsi, the third of which is bilobed. The larvce are soft, whitish or whitish-yellow, and either cylindrical or slightly flattened, with a large head and strong horny upper-jaws. In place of feet they mostly have six small wart-like tubercles. The pupa are spindle-shaped, and are easily recognisable from the long antennæ stretching backwards from the head. The beetle emerges from an oval exit-hole after boring obliquely upwards to the surface.
Life-history.—The beetles fly in summer and lay their eggs on the bark of trees, sometimes by means of an ovidepositor. When the larvæ hatch out they feed superficially at first, and then go deeper into the wood. Their borings are broad and shallow, but gradually enlarge as the larvæ increase in size ; and they are full of the bore-dust.
Generation is usually biennial; but it varies, being simple and annual in some species, and multi-annual in others.
The longicorn larvæ live chiefly in the wood of broad-leaved trees, and mostly attack sickly or unsound stems, so that the damage they do is therefore not great; but they sometimes riddle sound stems with holes, and depreciate their value as timber.
Only two species of Cerambyx are of any practical importance to the forester in Britain, namely :
1. The large Poplar Longicorn, Cerambyx (Saperda) carcharias, the larvæ of which chiefly infest Poplars and Willows up to about 20 years old. This is the commonest of the British longicorns (Fig. 157).
Appearance.—The beetle is about 1 to 14 inch long (with antennæ of about same length), clay.grey to yellowish brown, and with thorax and wing-cases covered with shining black spots. The round, legless, yellowish-white larvæ are about 1} inch long when full-grown, and have small heads with brown jaws and also brown plates on scales from the third to the tenth segment, while the neckshield is very conspicuous (Fig. 157 c; compare also Sesia apiformis, p. 121).
Life-history. The beetle Aies from June to August, being usually late in Britain. The female lays her eggs mostly on Poplars in bark-fissures near the
ground, and about four weeks later the larvæ hatch out and bore into the sapwood. Here they hibernate, boring deeper in the second year, and again hibernating as larvæ. During the following May or June pupation takes place, head downwards, in a pupal chamber formed by erecting a wall of bore-dust. After a pupal rest of
four weeks or more, the beetles emerge from June to Fig. 157
August for pairing and reproduction. The generation is therefore biennial, the larvæ feeding in the wood for two years.
Prevention and Extermination.—Saplings infested should be cut and burned before June. From June to August beetles may be shaken down from the trees, collected, and destroyed. The grubs may be extracted with bent wire ; and the bore-holes may be syringed with paraffin ; or cotton-wool, soaked in a strong solution of ammonia, may be rammed in and the bore-hole plugged up with putty; or the stems of young saplings, &c., in infested areas may
be smeared with patent tar. Large Poplar Longicorn. a. Beetle (natural size).
2. The small Poplar Longicorn, Cerambyx b. Larva (natural size).
(Saperda) populnea, is a common insect in Cenc. Head of larva (magnified).
tral and Southern England, where it often infests the branches of young Aspen and other Poplars, without, however, doing very much harm to them.
Appearance. - The beetle is only about an inch long, and black, with yellow or yellowish-grey hairs. The wing-cases have a central line and a broad stripe, with three or four downy spots on each side. The antennæ are blue and black, with white rings. The larvæ are yellow.
Life-history.—The beetles fly in May and June, and the females lay their eggs in bark-fissures on young 2- to 6-year-old Aspen saplings or suckers, also on other Poplars, and less frequently on Willows. The larvæ hatch out about four weeks later, and at first feed in the sapwood, but during the second year bore upwards into the pith, and cause the formation of spindle-shaped swollen nodes, which are very noticeable on the slender stems of Poplars, but do not form on Willows. After feeding for about two years, pupation takes place, and in May or June the beetle emerges by a circular hole bored in the middle of the swollen node. The generation is therefore also biennial.
Prevention and Extermination. Stems infested should be coppiced and burned, and the beetles should be shaken down in May and June, and destroyed.
The larvæ of another injurious species, Rhagium bifasciatum, is not uncommon in gate-posts and palings.
E. Saw-horn Beetles (Buprestide).—These are mostly long, thin, brightcoloured beetles with metallic lustre, compressed bodies, and short weak legs. It is only during their larval stage that they damage woodland-trees. They are not common in Britain, and none of them does much damage in our woods.
The beetles have usually hard wing-cases, tapering towards their upper ends, and short, 11-jointed, serrated antennæ (hence the name). The legless larvæ are white, soft, and elongated, and are either cylindrical or flat. They are somewhat like longicorn larvæ, but can be distinguished from these by their first segment being strongly developed, and often also by two horny tail-tips pointing outwards. They bore sinuous irregular galleries in the cambium and the sapwood, which broaden as the larvæ increase in size, and which are filled with bore-dust. Pupation takes place in a cocoon made of bore-dust and wood-chips in the sapwood at the end. On emerging from the pupal chamber, the beetle issues from the stem through a hole like a half-moon, flat on the upper side.
Generation. — Biennial.
The Green Beech Saw-horn Beetle, Buprestis (Agrilus) viridis, is the only species of any importance to the forester.
Appearance and Life-history-It is about of an inch long, and usually of blackish ground-colour, with a lustrous metallic blue, green, or olive sheen. It flies on bright sunny days in June and July. The female lays her eggs, either singly or in small clusters of 2 or 3, on the bark near the base of young Beech or Oak; and when the larvæ hatch out about four to six weeks later, they feed on the cambium, and either kill the saplings or make them sickly and cankeredlike. Strong Beech transplants are sometimes attacked while they are in rather a sickly condit before establishing themselves after being planted.
The larvæ hibernate inside the stems for two winters, then pupate in the cambium or the sapwood in the following April or May, and emerge from a halfmoon hole () with flat side above during June and July. The generation is therefore biennial.
Prevention and Estermination.—Plants attacked may be pulled up and burned before the beetles emerge in June.
F. Leaf-Beetles (Chrysomelidae).—This class of beetles, common all over Britain, and especially in the warmer parts, feeds on the foliage of many broadleaved trees, but seldom does much damage in woodlands, although one or two species can be rather destructive in Osier-beds. Both beetles and larvæ feed on foliage, gnawing away the soft tissues between the midrib and the veins, so that only the leaf-skeleton is left. Their work is thus very easily distinguished from that of other insects. Their attacks are usually confined to soft woods -Poplars, Willows, and Alders. The Osiers most injured are those belonging to the two species Salix purpurea and S. pentandra, and their varieties.
The beetles are usually small, and are short, squat, convex, strongly-arched, and oval or semi-globular in shape. They are often bright-coloured, and many have a metallic sheen ; abdomen with 5 segments; antennæ short, bead-like, and 11.jointed ; legs strong and adapted for springing. Larvæ short, flat, 6-legged, and usually black or variegated. Pupæ thickish, pear-shaped, often depending tail-end-up from leaves. Generation simple, annual.
1. The Red Poplar-leaf Beetle, Chrysomela (Lina) populi, is injurious both as beetle and larva, feeding on Poplar, Aspen, and Willow foliage, and often proving somewhat destructive in seriously retarding the development of the withes in Osier-beds.
Appearance. — The beetle is barely } an inch long, with a blackish-blue body, and brick-red wing-cases, tipped with black at their upper ends; antennæ short, compressed, and thickening considerably towards their ends. The 6-footed larvæ are dirty-white, with numerous black spots, and two white lateral processes on the second and third segments. The yellowish-brown pupa is marked with regular black spots and bands, and is somewhat pear-shaped, tapering off towards the tail-end. The pupæ hang head-downwards, and attached to leaves by their sharppointed tail-end.
Life-history.—The beetles fly in May and June, and the female lays from 100 to 150 eggs in clusters of 10 to 12 on the foliage of young saplings, stool-shoots,