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Associated with this weevil we have found the smaller, rounder, more cylindrical, whitish grubs of the Hylurgus terebrans, which mines the inner layers of the bark, slightly grooving the sap-wood. Later in April it pupates, and its habits accord in general with those of Pissodes strobi.
It was utterly without defenses against the little marauders who destroyed the bark and the sap-wood. And the sap-wood is necessary to the life of a tree because it carries the sap up to the very tips of the branches. There were stories of how whole forests had fallen victims to the race of boring-beetles.
There was the scent of freshly smitten bark and sap-wood in the air; the ground was paved with broad, clean chips. "Good-morning," said Westover. "How are you?" returned the other, without moving or making any sign of welcome for a moment. But then he lifted his axe and struck it into the carf on the tree, and came to meet Westover. As he advanced he held out his hand.
It was impossible that any one could discover this annular incision, made, not like a cut, but more like the ripping or gnawing of animals or those destructive insects called in different regions borers, or turks, or white worms, which are the first stage of cockchafers. These destructive pests are fond of the bark of trees; they get between the bark and the sap-wood and eat their way round.
The age is easily determined; the pith rays, or medullary rays, are also plain. These form what is called the silver grain of the wood. The ducts, also, are clear in the Oak and Chestnut. There is a difference in color between the outer and inner wood, the older wood becomes darker and is called the heart-wood, the outer is the sap-wood.
Arctia Arge, A. virgo, A. phalerata and other species fly from the last of May through the summer. Hyphantria textor, the Fall-weaver, is found in May or June. The White-pine weevil flies about in warm days. We have found its burrows winding irregularly over the inner surface of the bark and leading into the sap-wood.
The blocks should be cut eighteen inches long, and split into quarters, and the sap-wood dressed off. It is then ready for the frow as the instrument used for splitting shingles is called. A good splitter will keep two men shaving and packing. The proper thickness is four to the inch: the packing-frame should be forty inches long, and contain fifty courses of shingles, which make a thousand.
In the sap-wood, parallel with the surface of the trunk, under a layer of wood barely a twenty-fifth of an inch in thickness, it makes a cylindrical cell, rounded at the ends and roughly padded with ligneous fibres. A solid plug of shavings barricades the entrance, which is not preceded by any vestibule. Here the work of deliverance is the simplest.
Fortunately for the many uses to which its timber is put, the white pine grows very rapidly, gaining from fifteen inches to three feet every year. In deep and damp old woods it is slower of growth; it is then almost without sap-wood and has a yellowish color like the flesh of the pumpkin.
But the nourishment of dead leaves soon became unbearable, and likewise did the sap-wood, or second rind of young trees, such as elders and aspen trees, which they beat to a pulp between stones, have to be given up. At the time of the two previous famines, some wretched people were said to have supported themselves with a kind of fattish clay. Not far from Yvon's hut was a vein of such clay.
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