40G TILMUS CAMPESTRIS. 



after doing tliis, she dies, without making her way out atzain. as she may often 

 be fonnd dead at the end of the chamiel. About September, the larvie are 

 hatched, which commence feeding upon the matter of the inner bark, at the 

 edge of the channel : and, in a very shght degree, on that of the soft wood opj)o- 

 site. advancing, as they \'ccd, in a coiwse at about right angles from the j)rimary 

 chamiel. on each side of it. The true food of the insect is the inner bark ; and 

 tiie erosion of the soft W(to(l is so slight, as to l)e, jierhaps, nearly accidental. 

 The course of each individual larva, on each side of the primary channel, is 

 about parallel to that of the larva next to it ; and each forms a channel by its 

 feeding that is enlarged as the larva increases in size. When eacli larva ha: 

 finished its course of feeding, it stops in its progress, turns to a pupa, and then 

 to a beetle; and, in the latter state, gnaws a straight hole through the bark. 

 These beetles begin to come out in about the end of May, or the bcgiiming of 

 June, of the year following that in which the eggs were deposited. The sexes 

 afterwards pair, and the females, bearing eggs, pierce through the bark, as above 

 detailed : and so on, from generation to generation, and year to year. Tiie 

 result of the erosions of the female parent, and of the larvae, m the inner bark and 

 soft wood, is that of cutting off the vital connection between these two parts; 

 and. when the erosions effected in a tree have become numerous, of occasionmg 

 its death, by preventing the ascent and descent of the sap. It has been asserted 

 that the female scolytns never attacks a tree in a perfectly healthy state, for the 

 purpose of depositing her eggs ; and, also, that trees suffering under carcinoma 

 are particularly liable to her ravages. It has also been remarked that these 

 insects seldom destroy the trees they attack the first year; and that they prefer 

 a tree that they have already begun to devour, to one that is young and vigor- 

 ous ; but they never attack a tree that is entirely dead. Yet it is true that both 

 the males and females pierce yomig and healthy trees for the purpose of eating 

 the inner bark, which constitutes their principal food; and that the numerous 

 holes which they thus cause, partly from the loss of sap which exudes from them, 

 and partly from the effect of the rain that lodges in them, in a few years bring 

 the trees, in which they occur, into an incipient state of decay. These trees are 

 indiscriminately selected by the female insects for the deposition of their eggs, just 

 asin trees beginning to decay naturally; and thus healthy trees are effectually 

 destroyed by the combined operations, first and last, of the scolyti of both sexes, 

 though not in consequence of the sole deposition of the eggs of the female. The 

 most effectual mode recommended to prevent the future depredations of these 

 insects, is, first, to pare away, with a spoke-shave, or other tool, the rough exte- 

 rior bark of the trees bearing the marks of their ravages ; and if there be no trace 

 in the inner bark, either of small holes in old trees, or of those superficial furrows 

 which the scolyti of both sexes make for food in young trees, tbey may be pro- 

 nounced as being in a somid and healthy state. But if the inner bark exhibits 

 small holes which communicate with channels as described above, the next 

 thing to be done is to determine whether the female has already deposited her 

 eggs within it, or whether it contains the young scolyti either in a larva or 

 chrysalis state. In order to know this, it will be necessary to cut away, here and 

 there, portions of the bark, quite into the wood; and if the existence of either 

 the eggs or of the insects be proved, the trees should be cut down, and the bark be 

 taken off and burnt. Those trees pierced with exterior superficial holes or fur- 

 rows, which have no larvas in them, are such as have been attacked for food 

 only; and, if they be carefully brushed over with coal-tar, the fumes of which is 

 highly offensive to the perfect scolyti. there is every probability that they will be 

 secure from the future attacks of the females; and that the repetition of the same 

 process in the spring, for one or two years, would enable them to resume theii 

 vigour, and become healthy trees.* 



* See Loudon's Arboretum Britannicnm. iii., p. 1387, et seq. 



