Wood and Forest Part 38

[Ill.u.s.tration: Fig. 89. Work of the Spruce Destroying Beetle: _a._ Primary gallery; _b._ Borings packed in side; _c._ Entrance and central burrow thru the packed borings; _d._ Larval mines. Note how the eggs are grouped on the sides. [_Agric. Year Book_, 1902, Fig. 24, p. 268.]]

[Ill.u.s.tration: Fig. 90. Complete brood Galleries of the Hickory Bark Beetle in Surface of Wood. [_Agric. Year Book_, 1903, Fig. 28, p.

316.]]

[Ill.u.s.tration: Fig. 91. Brood Galleries of the Oak Bark Beetle, showing Character of Primary Gallery at _b_; Larval or Brood Mines at _a._ [_Agric. Year Book_, 1903, Fig. 30, page 318.]]

Many pairs of beetles make a simultaneous attack on the lower half of the main trunk of medium-sized to large trees. They bore thru the outer bark to the inner living portion, and thru the inner layers of the latter; they excavate long, irregular, longitudinal galleries, and along the sides of these at irregular intervals, numerous eggs are closely placed. The eggs soon hatch and the larvae at once commence to feed on the inner bark, and as they increase in size, extend and enlarge their food burrows in a general transverse but irregular course, away from the mother galleries (see ill.u.s.tration).

When these young and larval forms are full grown, each excavates a cavity or cell at the end of its burrow and next to the outer corky bark. (Hopkins, _Agric. Yr. Bk._, 1902.)

Some of the species attack living trees, causing their rapid death, and are among the most destructive enemies of American forests.

All of the above indirectly affect both the quant.i.ty and quality of the wood supply. They can be studied more in detail in the publications of the U.S. Bureau of Entomology.

Of the insects directly attacking wood, the most important are the ambrosia or timber beetles, the borers, the ants, and the carpenter bees. The most remarkable feature of the beetle is the manner of its boring into the harder parts of the wood. Its jaws are particularly constructed for this work, being heavy and strong. The boring is done something after the manner of countersinking, and the jaws are believed to be self-sharpening, by reason of the peculiar right to left and left to right motion.

_Ambrosia_ or _timber beetles_, Fig. 92. This cla.s.s of insects attacks living, dead, and felled trees, sawlogs, green lumber, and stave-bolts, often causing serious injury and loss from the pin-hole and stained-wood defects caused by their brood galleries. The galleries are excavated by the parent beetles in the sound sap-wood sometimes extending into the heart-wood, and the young stages feed on a fungus growth which grows on the walls of galleries. (Hopkins, Entom. Bulletin No. 48, p.

10.) The growth of this ambrosia-like fungus is induced or controlled by the parent beetles and the young are dependent on it for food. (Hopkins, _Agric. Yr. Bk._, 1904.)

[Ill.u.s.tration: Fig. 92. Work of Ambrosia Beetle, _Xyloborus celsus_, in Hickory Wood: _a_, Larva; _b_, Pupa; _c_, Adult beetle; _d_, Character of work in lumber cut from injured log; _e_, Bark; _f_, Sap wood; _g_, Heartwood. [_Agric. Year Book_, 1904, Fig. 44, p. 384.]]

[Ill.u.s.tration: Fig. 93. Work of Ambrosia Beetles in Oak: _a_, _Monarthum mali_, and work; _b_, _Platypus compositus_, and work; _c_, Bark; _d_, Sap-wood; _e_, Heart-wood; _f_, Character of work in lumber from injured log. [_Agric. Year Book_, 1904, Fig. 45, p. 384.]]

There are two general types or cla.s.ses of these galleries, one in which the broods develop together in the main burrows, the other, in which the individuals develop in short separate side chambers extending at right angles from the primary gallery, Fig. 93. The galleries of the latter type are usually accompanied by a distinct staining of the wood, while those of the former are not. (Hopkins, _Agric. Yr. Bk._, 1904, p. 383.)

_Bark_ and _wood borers_, Fig. 94. This cla.s.s of enemies differs from the preceding in the fact that the parent beetles do not burrow into the wood or bark, but deposit their eggs on the surface. The elongate, whitish, round-headed (_Cerambycid_), flat-headed (_Buprestid_), or short, stout (_Curculionid_) grubs hatching from these eggs cause injury by burrowing beneath the bark, or deep into the sap-wood and heart-wood of living, injured and dead trees, sawlogs, etc.

Some of the species infest living trees, Fig. 95, causing serious injury or death. Others attack only dead or dying bark and wood, but this injury often results in great loss from the so-called wormhole defects. (A. D. Hopkins, _Entom. Bull._, No.

48, p. 10.)

[Ill.u.s.tration: Fig. 94. Work of Round-Headed and Flat-Headed Borers in Pine: _a_, Work of round-headed borers, "sawyer," _Monohamnus_ sp.; _b_, _Ergates spiculatus_; _c_, Work of flat-headed borer, _Buprestis_, larva and adult. [_Agric. Year Book_, 1904, Fig. 46, p.

385.]]

[Ill.u.s.tration: Fig. 95. Hemlock Killed by Buprestid Worms. Hoquiam, Was.h.i.+ngton. _U.S. Forest Service._]

The pine sawyers are among the most troublesome pests in the mill yard, and their large, white larvae often do much damage to logs by eating great holes thru their solid interior. While burrowing in the wood the larvae make a peculiar grating sound that may be heard on quiet nights at a considerable distance.

This is a familiar sound in the lumber camps of the North, and has probably given rise to the name of the pine sawyers by which these insects are known. (_Forestry Bulletin_, No. 22, p. 58.)

_Powder-post beetles_, Fig. 96. This is a cla.s.s of insects representing two or three families of beetles, the larvae of which infest and convert into fine powder many different kinds of dry and seasoned wood products, such as hickory and ash handles, wagon spokes, lumber, etc., when wholly or in part from the sap-wood of trees. Oak and hemlock tan-bark is sometimes injured to a great extent, and the structural timbers of old houses, barns, etc., are often seriously injured, while hop poles and like products are attacked by one set of these insects, the adults of which burrow into the wood for the purpose of depositing their eggs. (Hopkins, _Forestry Bulletin_ No. 48, p. 11.)

[Ill.u.s.tration: Fig. 96. Work of Powder Post Beetle, _Sinoxylon basilare_, in hickory pole: _a_, Character of work by larvae; _b_, Exit holes made by emerging broods. [_Agric. Year Book_, 1904, Fig.

49.]]

_Timber worms_, Fig. 97. This cla.s.s of true wood-boring "worms," or grubs, are the larvae of beetles. They enter the wood from eggs deposited in wounds in living trees, from which they burrow deep into the heart-wood. Generation after generation may develop in the wood of a tree without affecting its life but the wood is rendered worthless for most purposes by the so-called wormhole and pinhole defects resulting from their burrows. The same species also breed in the wood of dying and dead standing trees, and in the stumps and logs of felled ones, often for many years after the trees are felled.

One species sometimes attacks freshly sawed oak lumber, new stave bolts, etc. They are among the most destructive enemies of hardwood forest trees, especially in reducing the value of the wood of the best part of the trunks. (Hopkins, _Forestry Bulletin_ No. 48, p. 10.)

[Ill.u.s.tration: Fig. 97. Work of Timber Worms in Oak: _a_, Work of oak timber worm, _Eupsalis minuta_; _b._ Barked surface; _c._ Bark; _d._ Sap-wood timber worm, _Hylocaetus lugubris_, and its work; _e._ Sap-wood. [_Agric. Year Book_, 1904, Fig. 47, p. 386.]]

The _carpenter worms_, Fig. 98. These are large pinkish caterpillars which are the larvae of stout-bodied moths. They enter the bark and wood of living oak, locust, poplar and other trees, from eggs deposited by the moths in the crevices of uninjured bark, or in the edges of wounds. They burrow deep into the solid wood, where they live for two or three years before transforming to the adult. The wood is seriously injured by the very large wormhole defects, and while the life of the tree is but slightly, if at all, affected by the earlier attacks, the continued operations of this cla.s.s of borers year after year, finally results in the decay of the heart-wood, or a hollow trunk and a dead top. (Hopkins, _Forestry Bulletin_, No. 48, p. 11.)

[Ill.u.s.tration: Fig. 98. Worm Holes in Red Oak, Work of the Oak Carpenter Worm. [_Agric. Year Book_, 1903, Fig. 37, p. 324.]]

_Columbian Timber-beetle_ One of the commonest wormhole defects in white oak, rock oak, beech, and tulip ("whitewood" or "yellow poplar") is one known to the lumber trade as grease spots, patch-worm, or black holes, Fig. 99, steam boats, Fig.

100, etc., caused by the Columbian timber beetle (_Corthylus columbia.n.u.s Hopk_.) The characteristic feature of this wormhole defect, which will enable it to be readily recognized in oak and beech, is transverse series of two or more black holes about the size of the lead in an ordinary lead pencil, with a streak of stained wood extending with the grain two or three or more inches each side, as in Fig. 99. In quarter-sawed oak or split or sawed staves, a short longitudinal section of one of these black holes is seen attended by the stained streak on one side of a thick or curly growth or grain, Fig. 100. It is this form which is called "steamboats." In whitewood (yellow poplar) the black holes are attended by very long black, greenish, or bluish streaks, sometimes five or six feet long. When this is common in the lumber it is called "calico poplar." Fig. 101 represents the characteristic appearance of this defect greatly reduced.

(Hopkins, _Agric. Yr. Bk._, 1903, p. 327.)

[Ill.u.s.tration: Fig. 99. Work of the Columbian Timber Beetle: Black holes and "grease spots" in white oak. [_Agric. Year Book_, 1903, Fig.

38, p. 325.]]

[Ill.u.s.tration: Fig. 100. Work of the Columbian Timber Beetle: "Steamboats" in quartered or Split white oak. [_Agric. Year Book_, 1903, Fig. 39, p. 326.]]

[Ill.u.s.tration: Fig. 101. Work of the Columbian Timber Beetle in Tulip Wood, "Calico Poplar," [_Agric. Year Book_ 1903, Fig. 40, p. 326.]]

_Carpenter bees._ The work of this cla.s.s of woodboring bees is shown in Fig. 102. The injury consists of large augerlike tunnels in exposed, solid dry wood of buildings and other structures. It is most common in soft woods, such as pine, poplar, redwood and the like. (Hopkins, _Agric. Yr. Bk._, 1904, p. 390.)

[Ill.u.s.tration: Fig. 102. Work of the Carpenter Bee, _Xylocopa orpifex_, in Redwood Lumber: _a_, entrance; _b_, galleries; _c_, cells; _d_, larva; _e_, adult. [_Agric. Year Book_, 1904, Fig. 53, p.

390.]]

_Horn tails._ This is a cla.s.s of borers which are the larvae of the so-called wood wasps. They may enter the exposed dead wood of wounds of living trees, but more commonly attack the wood of dead standing conifers and hard woods, in the sap-wood of which they excavate irregular burrows, which are packed with their borings. When the adults emerge they leave the surface perforated with numerous round holes. Water and fungi entering these holes cause a very rapid decay of the wood.

(Hopkins, _Entom. Bull._ No. 48, p. 11.)

The tunnels of these various wood pests are most frequently to be seen in chestnut, ash, hickory, oak, tulip, and cypress.

One would think that with such an array of enemies, the forest would hardly survive, but on the other hand there are many enemies of these pests. The most destructive are the predaceous and parasitic insects.

Many insects are simply predaceous, pouncing upon and destroying such other insects as they can overcome. Still others are parasites, some external, but most of them living within the bodies of their victims where they pa.s.s their entire larval life. The eggs are laid on or in the body of the victim, so that as soon as one hatches, it has suitable food. The ichneumon fly, Fig. 103, is such a parasite; it destroys millions of insect pests. It has a long and peculiar ovipositor with which it drills a hole into the tree and deposits the egg in a burrow of the Pigeon Horntail, a wood wasp that burrows into deciduous trees. The larva soon finds its victim, the grub of the Pigeon Horntail, and lives on it to its destruction.

[Ill.u.s.tration: Fig. 103. Ichneumon Fly whose Larva Feeds on the Larva of the Pigeon Horn-tail.]

It would seem that it is a hopeless task to control the insect enemies of forest trees and forest products or to prevent losses from their ravages, but the writer is informed by Dr. A. D. Hopkins, the expert in the Bureau of Entomology in charge of forest insect investigations, that the results of their investigations show conclusively that there are many practical and inexpensive methods of control now available thru the suggestions and recommendations in recent Department publications on forest insects, as well as thru direct correspondence with the Department. These methods are based on the principle of prevention and not on that of extermination. It has been shown that thru proper adjustment of the details in management of forests and of the business of manufacturing, storing, transporting, and utilizing the products a large percentage of the losses can be prevented at small additional expense, and that even when considerable cost is involved the amount saved will often represent a handsome profit.

THE NATURAL ENEMIES OF THE FOREST.

REFERENCES:[A]

(1) Meterological.

Pinchot, _Primer_ I, pp. 75-76.

Roth, _First Book_, _pp._ 198-202.

Bruncken, pp. 27-29.

Water.

Roth, _First Book_, p. 27.

Snow, ice and frost.

Pinchot, _Primer_, I, p. 76.

Bruce, _For. and Irr._, 8: 159, Ap. '02.

(2) Vegetable.