Page:A primer of forestry, with illustrations of the principal forest trees of Western Australia.djvu/112

106 annually is very considerable. Insects cause stunted growth and deformity and at times kill trees- outright. Insects are the cause of damage to trees right from the nursery to the cutting or felling, and after the logs the converted into the finished product, or even after it is placed in the finished article or structure. Insect-destroyed timber furnishes fuel for forest fires which not only destroy the dead timber, but injure and make susceptible to further insect attack, much of the green living timber. It is well known that owing to the inroads of boring insects into timber, deterioration and decay are more rapid than would otherwise be possible. In every forest there is an ever present but inconspicuous army of insects which live upon the bark, wood, foliage, seeds, and roots of the trees.

Trees damaged by fire or scarred by falling limbs or trees of unhealthy growth through unsuitability to soil, are usually the first to be attacked as they offer the least resistance.

In the following notes only the brief outline of a few species of local destructive forest insects is given, all unnecessary or minute details being avoided. To enumerate the various pests of the forest would require a huge volume.

Coleoptera Beetles.-—These are no doubt the greatest offenders in our forests, and of these the most numerous are the weevils (Curculionidae), or commonly known as the Snouted or Elephant Beetles.

The Long Horned Beetles (Longicornes) are also a large and destructive group.

Some of the most dreaded of forest insects are contained in the Scolytidae.

Wood Borers.

The Bostrychidae, or Augur Beetles, are a well represented group.

The Buprestidae, commonly known as Jewel Beetles, are very destructive to various timbers.

We will take these beetles in the order referred to.

Weevils (Curculionidae) can readily be distinguished from other beetles by the head which terminates in a snout. Their mode of attack is as varied as the group itself; some attack only dying or dead trees, while others take the living plants. The larvae burrow or tunnel the roots, trunk, twigs, or they may cause galls or swellings to appear on the branches within which they live. The adult beetles may be foliage, bark, bud, fruit nibblers, or feed upon stored foods. Some adults have the power of flight, but many have lost that power.

One of the commonest examples of a weevil is one known as the Grain Weevil (Calandra oryzae). This insect lives and breeds in cereals or grains. A typical tree-destroying weevil and one having a wide range over Australia is (Orthorrhinus cylindrirostris). The larvae of this beetle bore through the centre of the limbs and pupate therein, causing, when numerous, the death of the tree. Not only forest trees are attacked, but it has been found in our State attacking fruit and ornamental trees.

The Longicorns or Long-horned Beetles (Cerambycidae) .—The most numerous and characteristic are the members of the Genus (Phoracantha). The life histories and general habits of all longicorn beetles are nearly identical. The perfect beetles hide in the daytime under dead bark or resting on tree trunks. When captured some of them produce a sharp rasping sound. They are nocturnal, that is, night flying, coming out from their hiding places just about dusk. They are powerful fliers and often attracted to lights. The colour is usually shiny black or reddish brown and often mottled or blotched with pale yellow. The general form of these beetles is elongate, antennae long and stout. The eggs are laid upon the bark in cracks or under loose bark. The little larvae, so soon as they hatch, bore their way through the bark where they remain feeding for some time upon the sap wood.