33 Studies in Forestry [CHAP. xiv. 



hairy kinds like those of the Pine moth, owing to the irritant 

 properties of the hairs. 



It is only when deposited low down on the stem that the 

 ova of species like the Spruce moth can practically be col- 

 lected and destroyed ; but under any circumstances, and espe- 

 cially on the fissured bark of Pine trees, many eggs and clusters 

 of ova are apt to be overlooked. Prof. Altum, a celebrated 

 sylvicultural entomologist of Northern Germany, recommends 

 a daub of viscous tar as efficacious in killing the clusters of 

 ova of species like the Spruce and Gipsy moths (Liparis 

 monacha and L. dispar) and the Beech-spinner (Dasychira pudi- 

 bunda). 



Attempts to collect and destroy the restless moths them- 

 selves can in no way be considered at all satisfactory. A good 

 many experiments were made in Bavaria in 1891 with strong 

 electric lights placed before powerful exhaustors, but without 

 any practical results being attained with the Spruce moth. 



As previously remarked, bad attacks of moths seldom last 

 for longer than three years in their full destructive intensity*. 

 But within that time enormous damage may be committed, 

 and vast sums may have to be incurred for fighting against the 

 moths. The latter are also almost always followed by enormous 

 numbers of bark-beetles, cambial-beetles, and weevils, whose pro- 

 lificness is stimulated by the vast quantities of dead, felled, and 

 sickly timber which litters the woods in quantities not removable 

 all at once. These vast breeding-places, sooner or later, attract 

 such large flights of insectivorous birds, that market-gardeners 

 and orchard-owners in other localities begin to complain of 

 insect pests owing to the departure of starlings, finches, &c. ; 

 whilst at the same time the balance of nature re-asserts itself 

 by epidemics of fungoid diseases and through any unusual 

 prolificness among the Ichneumonidae and Tachinidae. 



Too much stress cannot be laid on the importance of the 

 early discovery of any, even apparently slight, increase in the 



