166 PROTECTION OF WOODLANDS. 



the needles down to the sheaths enclosing them, and in bad years, 

 when the foliage becomes totally denuded, destroying even the 

 young buds, in which latter case the crop is naturally killed. So 

 long, however, as they can still get food elsewhere, the voracious 

 caterpillars, whose requirements in the way of forage are indeed 

 very considerable, spare the young shoots. 



The pupal rest is entered into about the end of June, the 

 chrysalides occupying the fissures in the bark, where the flakes 

 of dead rind stand out prominently from the stem, or else the 

 cocoons are formed up among the branches in the crown. The fully- 

 developed moths make their appearance after a pupal rest of 

 about three weeks. This moth lives only on Pines, chiefly Scots 

 Pine, and principally attacks crops of older growth on soils 

 of inferior quantity, as these are especially favourable to the 

 hibernation of the caterpillars ; but when reproduced in large 

 numbers it also naturally attacks younger crops, such as pole- 

 forests, and even young thickets and new plantations. It belongs 

 to the most injurious class of forest insects, and has at various 

 times committed enormous devastations in the Scots Pine forests 

 that cover such a great extent of country throughout the North 

 German Plain, as also in the large Pine forests of the same 

 species which occur here and there in Southern Germany, 

 absolutely ruining vast stretches of woodlands by totally de- 

 nuding them of foliage. In such localities the forester and the 

 sylviculturist have every reason to bestow very careful attention 

 on this insect wherever it makes its appearance. 



The formation of mixed woods has been recommended as a 

 preventive measure, for it is well known from experience that the 

 individual species are then least exposed to attacks, and suffer far 

 less from insect enemies than when grown in pure forests ; but on 

 the poor classes of sandy soil to which the Scots Pine is so often 

 assigned, there are such difficulties in the way of getting other 

 species to thrive as to render this measure often quite impracti- 

 cable. 



A constant and careful revision of the whole of the growing 

 stock, and not merely of a few of the annual crops, is a most 

 important protective measure, so that wherever any considerabB 

 increase of the insect is to be feared, prompt action may be taken 

 to obviate the otherwise certain results. In addition to keeping a 

 look-out at the usual time of the swarming of the moths, and to 



