44 FIRST ANNUAL REPORT OF 



afterwards. These young worms differ in no essential from the full 

 grown specimens, except in their very minute size ; and they invari- 

 ably live, for the first year of their lives, on the sap-wood and inner 

 bark, excavating shallow, flat cavities which are found stuffed full of 

 their sawdust-like castings. The hole by which the newly hatched 

 worm penetrated is so very minute that it frequently fills up, though 

 not till a few grains of castings have fallen from it; but the presence 

 of the worms may be generally detected, especially in young trees, 

 from the bark, under which they lie, becoming darkened, and suffi- 

 ciently dry and dead to contract and form cracks. Through these 

 cracks, some of the castings of the worm generally protrude, and fall 

 to the ground in a little heap, and this occurs more especially in 

 the spring of the year, when, with the rising sap 3iid frequent rains, 

 such castings become swollen and augment in bulk. Some authors 

 have supposed that the worm makes these holes to push out its own 

 excrement, and that it is forced to do this to make room for itself; but, 

 though it may sometimes gnaw a hole for this purpose, such an in- 

 stance has never come to my knowledge, and that it is necessary to 

 the life of the worm is simply a delusion, for there are hundreds of 

 boring insects which never have recourse to such a procedure, and 

 this one is frequently found below the ground, where it cannot possi- 

 bly thus get rid of its castings. It is currently supposed that this 

 borer penetrates into the heart wood of the tree after the first year of 

 its existence, whereas the Flat-headed species is supposed to remain 

 for the most part immediately under the bark ; but I find that on these 

 points no rules can be given, for the Flat-headed species also frequent- 

 ly penetrates into the solid heart wood, while the species under con- 

 sideration is frequently found in a full grown state just under the in- 

 ner bark, or in the sap-wood. The usual course of its life, however, 

 runs as follows : 



As winter approaches, the young borer descends as near the 

 ground as its burrow will allow, and doubtless remain inactive till 

 the following spring. On approach of the second winter it is 

 about one-half grown and still living on the sap-wood; and it is at 

 this time that these borers do the most damage, for where there are 

 4 or 5 in a single tree, they almost completely girdle it. In the course 

 of the next summer when it has become about three-fourths grown, 

 it generally commences to cut a cylindrical passage upward into the 

 solid wood, and before having finished its larval growth, it invariably 

 extends this passage right to the bark, sometimes cutting entirely 

 through a tree to the opposite side from which it commenced; some- 

 time turning back at different angles. It then stuffs the upper end of 

 the passage with sawdust-like powder, and the lower part with curly 

 fibres of wood, after which it rests from its labors. It thus finishes its 

 gnawing work during the commencement of the 3d winter, but re- 

 mains motionless in the larval state till the following spring when it 

 casts off its skin once more and becomes a pupa. After resting three 



