132 Studies in Forestry [CHAP. vi. 



or Spruce moth (Liparis monachd) which together with the 

 bark-beetles (Bostrychini and Hylesinini} that followed it and 

 attacked the stems left in a sickly condition of growth between 

 1853-1862 devastated the coniferous forests of eastern Prussia 

 and western Russia over about 7,000 geographical square 

 miles, and necessitated the felling of over 420,000,000 cubic 

 feet of timber, Hess recommends 1 , as the first measure of 

 prevention, ' avoidance of the formation of pure forests of Spruce 

 or Scots Pine ; formation of mixed crops of suitable species. 1 

 This same insect has quite recently, in southern Bavaria and 

 western Austria (1889-1891), necessitated the clearance of 

 40,000 acres, mostly of pure Spruce; and during 1892 an 

 outlay of 75,000 was incurred solely in order to combat its 

 further attacks in the State Forests of Bavaria alone 2 . 



That the calamitous extent to which attacks by moths 

 (Bombycidae), bark-beetles (Scolytidae\ and weevils (Curcu- 

 lionidae] occur every now and again in Germany, arises from 

 the want of natural admixture of different species is a fact 

 which receives practical recognition in the endeavours now 

 everywhere being made in order to effect a re-transformation 

 to the former mixed state of the woodlands. As Gayer 

 says * : 



' Endeavours are in general being made to prepare the way for 

 a return to mixed forests in all suitable localities. And that, face to face 

 with the late fearful devastations (by insects) in the Spruce forests of 

 southern Bavaria, these principles should be even more strongly insisted 

 on, can easily be understood.' 



It is a well-known matter of experience that forests of broad- 

 leaved species are not exposed in anything like the same degree 

 to serious damage from insects. Even after crops may have 

 been stripped of their spring flush of leaves as sometimes 



1 Der Forstschutz, vol. i., 1887, p. 355. 



2 A detailed account of this moth and its ravages will be found in the 

 Transactions of the Highland and Agricultural Society of Scotland, 1893, 

 pp. 176-207. 



3 Zeitschrift fur Forst- und Jagdwesen, 1892, p. 386. 



