INSECTS INJURIOUS TO CONIFERiE. 



151 



among Coniferse alone among trees, and among the forest- 

 species of Pine, Fir, and Larch — for the Yews, Cypresses, 

 Thuyas, &c., do not now concern us — that have happened those 

 repeated instances of widespread destruction over large forest 

 areas which, occurring even before economic forestry began to 

 change the character of the primitive mixed woods, probably 

 increased in number and severity at that epoch, and have con- 

 tinued at intervals to the present day. 



A striking example of this destruction is that which 

 happened in the period 1853-68 in East Prussia, Poland, and 

 Eussia, when the Spruce was killed over an area of 7,000 

 square German miles. A similar instance is that afforded last 

 year in the Bavarian forests by the plague of the same destruc- 

 tive insect {Liparis monacha) ; the loss caused by this to the 

 revenue was estimated at £40,000. 



The immense importance of these attacks has given an 

 impetus to the study of forest-insects on the Continent, and 

 a not inconsiderable mass of literature has sprung up. In this 

 the foremost place must be given to the works of Katzeburg, who 

 was the first to place this branch of entomology on a truly 

 scientific basis. His books, from the monumental Forst- 

 Insekten " (1839) to the equally remarkable sequel "Die 

 Waldverderbniss " (1868), are a testimony to his unwearied 

 industry and success in the collection of facts and the study of 

 obscure life-histories, and of his capacity for marshalling these 

 so as to deduce important general principles ; while the idea of 

 the " struggle for existence " running through them demands 

 that everyone who seriously studies this later conception shall 

 be acquainted with their contents. 



Of the two books referred to, " Die Forst-Insekten " is con- 

 cerned with the life-histories and habits of injurious insects. In 

 some respects this work is out of date, as is the case with all 

 entomological works of that period ; but the numerous details 

 given, the original descriptions of species and the excellence of 

 the illustrations, at least in an original copy and not in a badly 

 coloured reprint, make it a classic. "Die "Waldverderbniss " deals 

 with the effect on the trees of insect-attacks, and is especially 

 valuable for the plates, which form a unique atlas of vegetable 

 pathology illustrating the altered appearance both of stems, 

 branches, &c., damaged by insects or mammals, and that of 



