16 THE GIPSY MOTH AS A FOREST INSECT. 



them die and even take on new life and vigor through coining mto a 

 larger share of light and space. It is yet to be determined whether 

 these trees are more resistant or whether, through standing ui some 

 favored pockets of richer soil, they simply survive through the pos- 

 session of a more vigorous constitution. 



It is undoubtedly true that vigorous, rapidly growmg trees are 

 more resistant than other trees of the same species less vigorous 

 and less rapidly growing. Thus oak trees around the border of an 

 infested wood lot, ^\^th more room to expand their roots and branches, 

 not infrequently live when all or nearly all the more crowded indi- 

 viduals in the depths of the wood lot die. It is also true that isolated 

 trees withstand a greater degree of defoliation than those in dense 

 growth. 



Advantage seems to have been taken of this principle in the method 

 of growing oak formerly in vogue in Germany, for, if the writer is 

 correctly mformed, the finest and largest oaks in the Empire are 

 grown more or less isolated and parked. When the relative immu- 

 nity of young spi-outs is also considered, a very logical reason is 

 suggested for the fact that the method of leaving reserve trees, 

 scattered over a territory devoted principally to the growth of sprouts 

 or coppice, finds so much favor in certain parts of Europe. These 

 reserve trees are left practically isolated in the forests which have 

 come to the writer's personal attention, and the sprouts, for wliich 

 there is a ready market, unfortunately lacking in America, are cut 

 at quite frequent intervals. 



SUGGESTIONS FOR THE MANAGEMENT OF FOREST LANDS WITH REFER- 

 ENCE TO THE GIPSY MOTH. 



It is by no means to be understood that because of the gipsy moth 

 all the oak in this country is foredoomed to destruction, but atten- 

 tion must be called to what is undoubtedly the truth, that unless 

 parasitism or disease, or something else not at present recognized as a 

 variable factor in the natural control of this pest, develops to an 

 extent unknown in either America or Europe, pure and mixed stands 

 of oak wdll be seriously injured. Not only is the oak itself liable to 

 injury, but also other trees mixed vnih it. 



It is 3^et too soon to state definitely whether, in localities where 

 there is no oak, other trees may not act as breeders of the moths to 

 an equally disastrous extent. For instance, the paper birch in the 

 north woods may so foster it as to bring about the defoliation of 

 adjacent spruce. The results of field-observation work in occasional 

 bits of forest in the infested territory where spruce and bii'ch occur 

 are not in themselves sufficient to settle the question, because condi- 

 tions so far from the large body of boreal forest can not be considered 



