_ INDIRECT INJURIES CAUSED BY INSECTS. 213 



important part in such vast numbers, 80,000 being some- 

 times found in a single tree, that it is infinitely more 

 noxious than any of those that bore into the wood : and 

 such is its vitality, that though the bark be battered and 

 the tree plunged into water, or laid upon the ice or snow, 

 it remains alive and unhurt. The leaves of the trees 

 infested by these insects first become yellow, the trees 

 themselves then die at the top, and soon entirely perish. 

 Their ravages have long been known in Germany under 

 the name of Wurm trokniss (decay caused by worms) ; and 

 in the old liturgies of that country the animal itself is 

 formally mentioned under its vulgar appellation, " The 

 Turk." This pest was particularly prevalent and caused 

 incalculable mischief about the year 1665. In the begin- 

 ning of the last century it again showed itself in the 

 Hartz forests it reappeared in 1757, redoubled its in- 

 juries in 1769, and arrived at its height in 1783, when 

 the number of trees destroyed by it in the above forests 

 alone, was calculated at a million and a half, and the 

 inhabitants were threatened with a total suspension of 

 the working of their mines, and consequent ruin. At 

 this period these Bostrichi, when arrived at their perfect 

 state, migrated in swarms like bees into Suabia and Fran- 

 coma. At length, between the years 1784* and 1789, in 

 consequence of a succession of cold and moist seasons, 

 the numbers of this scourge were sensibly diminished. 

 It appeared again however in 1790, and so late as 1796 

 there was great reason to fear for the few fir-trees that 

 were left a . 



* Wilhelm's Recreations from Nat. Hist, quoted by Utreille Hist, 

 Nat. xi. 194. 



