DAMAGE CAUSED BY ANIMALS. 127 



From the above it will be seen how important it is to make a 

 timely discovery of the presence of lepidopterous enemies, so as 

 to take immediate measures against their spread. We may thus 

 avoid the necessity for resorting to exterminative measures on a 

 large and costly scale during the third year, and, at the same 

 time, obviate the loss attendant on any extensive calamities. 



Of course, in estimating the measures that appear advisable in 

 regard to checking the attacks of any kind of injurious insect, 

 due consideration must be given as to the actual necessity for 

 adopting special measures, and as to whether the object in view is 

 likely to justify the necessary outlay ; for only in the latter case 

 can costly methods of annihilation be justified. The number of 

 injurious insects present within the woods, a point by no means 

 always easy to determine, the health and the vigour of the crops 

 in resisting attacks from parasitic and fungoid growth, the value 

 and general condition of the woods attacked or threatened, and, 

 finally, the prospect of a more or less satisfactory and successful 

 conduct of the preventive and remedial measures that seem 

 advisable after due consideration of the probable extent of the 

 danger, of the necessary outlay, and of the amount of labour 

 standing at one's disposal, must in each special case determine 

 which annihilative measure seems most desirable, and to what 

 extent the war must be waged against the insect enemies. 



62. Treatment of damaged Timber Crops, and of Timber felled in 

 consequence of Injuries. 



Only crops of Pine and Spruce are apt to be damaged to such 

 an extent as to necessitate felling or clearance on an extensive 

 scale. Silver Fir and Larch, as a rule, suffer to a much less degree, 

 and mostly from less injurious insects, whilst broad-leaved species 

 of trees, owing to their greater recuperative power, can withstand 

 even total denudation of their foliage. 



Whenever any extensive damage is being committed by insects, 

 it is of great importance to note whether the trees are being fatally 

 injured or not. In the former case, any delay in utilising and 

 preparing them for sale injuriously affects the quality of the timber, 

 whilst in the latter, by felling too precipitately, there is the danger 

 of not only glutting the mart with one particular class of timber, 



