CHAP, xiv.] Insect Enemies 329 



bark, so that the glue may bite well on to the stem evenly all 

 round without so much being required as on rough-barked 

 stems. This cleaning, or ' reddening ' as it is called in the 

 case of the Scots Pine, takes place with iron scrapers at about 

 breast-height, where a girdle about 4 inches is cleared, care 

 being taken not to injure the stem by too rough treatment. 

 This preparation should take place in winter and early spring 

 in all crops where inspection has shown that Pine moth cater- 

 pillars are hibernating under the moss, or that deposits of 

 Spruce moth ova are noticeable on the stems. About the end 

 of March or the beginning of April the formation of the rings 

 of patent tar should take place before any mild spring weather 

 has quickened the ova to life or the caterpillars to renewed 

 activity. It may be applied with hard brushes ; but the best 

 results were attained in Bavaria by the use of small wooden 

 spuds about i to ij inches broad, the rings or bands being 

 smoothed off with similar spuds hollowed to a depth of about 

 Jth of an inch. Wherever convenient, a thinning out of the 

 crop should first take place so as to remove all individual 

 poles or stems not actually necessary for the maintenance of 

 the full leaf-canopy or of the productive capacity of the soil. 

 This not only reduces the cost of the operation materially, 

 but also removes the class of stems most likely to favour the 

 increased propagation of the insects. 



Even in the case of species whose caterpillars hibernate 

 on the ground (e. g. Pine moth) the removal of the soil-cover- 

 ing of moss has been found to do more harm than good, as it 

 rapidly exposes the soil to deteriorating influences. 



The collection of the chrysalides by hand is only practicable 

 when they are formed on shrubs or in fissures of the bark 

 near the base of stems, and can hardly be carried out on any 

 large scale. A much more efficacious method consists in the 

 driving in of swine into the woods. They eagerly devour all 

 smooth-skinned pupae like the Pine Beauty and the Pine 

 Span-worm lying under the moss, although they will not touch 



