298 



PROTECTION AGAINST INSECTS. 



first year and become successively smaller and weaker, rapidly 

 ensue. At the same time, insect-parasites and bacterial 



diseases become 

 more and more 

 active, until the 

 caterpillars die 

 from these causes 

 in immense num- 

 bers. 



This pest is most 

 dangerous in pure 

 Scots pine forests, 

 on sandy soils, in 

 dry districts, and 

 in the plains and 

 hills of North and 

 North-eastern Ger- 

 many, less so in 

 the south and west; 

 it is rare in moun- 

 tainous districts. 



A succession of 

 warm summers 

 favours its multi- 

 plication to an ex- 

 traordinary degree. 

 In the ten years, 

 186372, in the 

 forests from West 

 Prussia to Saxony, 

 442,500 acres of 

 Scots pine forests 

 were attacked, and 

 70,000,000 cubic 

 feet of timber 

 killed. In 1888-9, 



the valleys of the Rhine and Maine, in Hesse, were ravaged, 

 and the caterpillars devoured the needles even of 10-year-old 

 pines. 



Fig. 149. Rosette-needles (#) on Scots pine, following 

 defoliation by G. pini, Ochsh. (Natural size.) 



