INJURY TO THE FOREST BY INSECTS. 131 



writers ascribe to insect life an importance wliich it has not reached 

 in America, where the spontaneous woods are protected by safe- 

 guards of nature's own devising. 



The insects which damage primitive forests by feeding upon 

 products of trees essential to their growth, are not numerous, nor 

 is their appearance in destructive numbers frequent, while those 

 which perforate the stems and branches, to deposit and hatch their 

 eggs, more commonly select dead trees for that pm^pose, though, 

 uiohappily, there are important exceptions to this latter remark.* 

 I do not know that we have any evidence of the destruction or 

 serious injury of American forests by insects, before or even soon 

 after the period of colonization ; but since the white man has laid 

 bare a vast proportion of the earth's surface, and thereby pro- 

 duced changes favorable, perhaps, to the multiphcation of these 

 pests, they have greatly increased in numbers, and, apparently, in 



* The locust insect, Cliius pictus, whicli deposits its eggs in the American 

 locust, Robinia pseudacacia, is one of these, and its ravages have been and stUl 

 are most destructive to that very valuable tree, so remarkable for combining 

 rapidity of growth with strength and durability of wood. This insect, I be- 

 lieve, has not yet appeared in Europe, where, since the so general employment 

 of the BoMnia to clothe and protect embankments and the scarps of deep cuts 

 on railroads, it would do incalculable mischief. As a traveller, however, I 

 should find some compensation for this evil in the destruction of these acacia 

 hedges, which as completely obstruct the view on hundreds of miles of French 

 and Italian railways, as do the garden- walls of the same countries on the ordi- 

 nary roads. 



The lignivorous insects, that attack living trees, almost uniformly confine 

 their ravages to trees already unsound or diseased in growth from the depreda- 

 tions of leaf -eaters, such as caterpillars and the like, or from other causes. The 

 decay of the tree, therefore, is the cause, not the consequence, of the invasions 

 of the borer. This subject has been discussed by Perris in the Annales de la 

 Societe Entomologique de la Finance for 1853, and his conclusions are confirmed 

 by the observations of Samanos, who quotes at some length the views of Per- 

 ris. " Having, for fifteen years," says the latter author, " incessantly studied 

 the habits of lignivorous insects in one of the best wooded regions of France, 

 I have observed facts enough to feel myself warranted in expressing my con- 

 clusions, which are : that insects in general — I am not speaking of those which 

 confine their voracity to the leaf — do not attack trees in sound health, and they 

 assail those only whose normal conditions and functions have been by some 

 cause impaired." 



See, more fully, Samanos, Traite de la Culture du Pin Maritime, Paris, 1864, 

 pp. 140-145, and Siemoni, Manuale dell' Arte Forestale. 2d edition. Florence, 

 1872. 



