DAMAGE CAUSED BY ANIMALS. 125 



thinning operation previously, so as to remove all individuals not 

 absolutely necessary for the wellbeing of the crop, this will 

 contribute very materially to a saving in labour and in patent 

 tar, as well as removing a class of stems favourable beyond all 

 others for the propagation of the insects. 



The action of good patent tar is repellent, owing either to its 

 smell or its taste. The caterpillars either have not the courage to 

 attempt to cross the rings, when they perish of hunger below them, 

 or they remain caught in them, owing to their viscosity, or if they 

 succeed in crossing, they soon die in consequence of their feet and 

 mandibles being clogged with the gluey composition. 



A measure that formerly found extensive application, consisted 

 in the removal from the woods of the soil-covering of moss (for 

 cattle-bedding, &c.), when many hibernating caterpillars (e.g., 

 Pine moth) were at the same time removed, and many others 

 were killed by exposure to the cold ; but experience has shown that 

 it is not very effective. And as it is obviously most prejudicial to 

 the well-being of the woods, and the productive capacity of the 

 soil, it has now been given up wherever formerly practised. 



The chrysalides can only be collected when situated low down 

 on the stem in the fissures of the bark, or when attached to shrubs ; 

 but on the whole their collection is not generally practicable on 

 any very large scale. In destructive measures against certain 

 species, as for instance the Pine Owlet-moth (Trachea piniperda), 

 and the Pine Span-worm (Fidonia piniaria), the driving in of 

 swine into the woods is a much more effective way of getting rid 

 of all smooth-skinned chrysalides lying under the moss ; for these 

 are eagerly devoured by swine, although they will not touch the 

 hairy species like the Pine moth (Gastropacha pini), owing, most 

 probably, to the irritant properties of the hairs. 



Ova can only be collected when they have been deposited in 

 large numbers on the lower portion of the stem, as in the case of 

 the Spruce moth (Liparis monacha), and under any circumstances 

 many eggs and clusters of eggs are apt to be overlooked, especially 

 in Pine woods, owing to the deeper fissures in the bark than on 

 Spruce or Silver Fir stems. The clusters of ova are more readily 

 noticeable when they have cobweb-like filaments attached, as in the 

 case of certain species feeding on the broad-leaved kinds of trees, and 

 Altum recommends the coating over of such clusters of eggs with 

 patent tar for the purpose of killing them ; this may be done with 



