Another troublesome insect is the _Scolytus destructor_, which makes its radiating tunnels between the bark and the tree. Whole forests have been destroyed by this voracious little beetle, the bark having been completely detached, and the tree necessarily killed. The habits of this beetle are well described in the following passage.] [Illustration: Bark mined in rays by beetle-grubs.] We have frequently observed a very remarkable instinct in the grubs of a species of beetle (_Scolytus destructor_, Geoffroy), which lives under the dead bark of trees. The mother insect, as is usual with beetles, deposits her eggs in a patch or cluster in a chink or hole in the bark; and when the brood is hatched, they begin feeding on the bark which had formed their cradle. There is, of course, nothing wonderful in their eating the food selected by their mother; but it appears that, like the caterpillars of the clothes-moth, and the tent insects, they cannot feed except under cover. They dig, therefore, long tubular galleries between the bark and the wood; and, in order not to interfere with the _runs_ of their brethren, they branch off from the place of hatching like rays from the centre of a circle: though these are not always in a right line, yet, however near they may approach to the contiguous ones, none of them ever break into each other's premises. We cannot but admire the remarkable instinct implanted in these grubs by their Creator; which guides them thus in lines diverging farther and farther as they increase in size, so that they are prevented from interfering with the comforts of one another. [We now come to one or two of the beetles which bore deeply into the very wood of the trees. As a rule, the musk-beetle keeps rather towards the exterior of the tree, but there are many that are not so cautious, and which besides damage the tree additionally by nibbling a quantity of chips, wherewith they strengthen their cocoons. We will first take the two insects which are shown in the accompanying illustration. That on the right hand is a species of weevil, or Curculio, and is an undescribed species belonging to the genus Rhyncophorus. It is a native of Australia. The insect and its cocoon are drawn one third less than their real size. The colour of the beetle is warm chestnut brown, and the bold marks on the thorax are jet black. In its larval state it burrows into the palm-trees, and when about to assume the pupal condition it makes the remarkable cocoon which is figured. Generally, these wooden cocoons are made of little chips which are bitten from the wood, and woven together with silk. This cocoon, however, is made of long fibres, which are torn rather than bitten, and are so long that one of them will sometimes encircle the cell three times, making an average length of nine inches. It is tolerably compact in structure, and the colour is pale brown.