12 PROTECTION OF PLANTS, 1921-22 



work: "Forest Insects" — Part I, appearing in 1837, Part II, in 1840, and Part 

 III, in 1845. This great work was the result of ten years of uninterrupted 

 study of many widely-scattered notes on forest insects and of ten years of 

 personal and correspondence touch with foresters, forest people and forest 

 insects. 



In the years 1844, 1848 and 1852 appeared "The Ichneumons of Forest 

 Insects" in three Volumes, perhaps the best known of Ratzeburg's works — 

 — especially to entomologists. 



Realizing that his "Forest Insects" would be too expensive for the average 

 library and student, Ratzeburg had prepared a smaller book — "Forest Des- 

 troyers and Their Enemies". This book was published in 1841 and had reached 

 its 6th edition in 1869. 



Ratzeburg's plan was to investigate not only all injuries to trees by insects, 

 but those resulting from physiological and pathological causes. To this end, 

 he published in 1862 "The Dissases and Reproduction of the Pine as a Re- 

 sult of the Attack of the Trachea piniperda, the Forl-Eule", but he soon real- 

 ized that it was impossible for any one man to deal adequately with the Phy- 

 siology and Pathology on account of the rapid advances that were being made 

 in these sciences at that time. 



In 1866 he published Part I of a magnificent work entitled "Forest Injury 

 or Losses inflicted by Insect Attacks, etc." Part, II, appearing in 1868. 



In May 1869, after 39 years of most useful, unselfish activity as a teacher, 

 Ratzeburg took a well-earned rest; moreover, his health rendered such a 

 proceeding necessary. Already he had begun another work entitled "A Forestry 

 Lexicon for Authors", and the manuscript was ready for the press at the time 

 of his death in October 1871. Thi^ work appeared in 1872. 



Beside the Hst of publications that have been mentioned, Ratzeburg 

 published several smaller works on allied botanical and zoological subjects. 



In the words of Phoebus, his life-long friend, "he erected a Dankmal, 

 a monument more lasting than brass". It is not exceeding the truth to say that 

 Ratzeburg's work stands as the greatest single contribution to forest entom- 

 ology. Judeich and Nitsche's work on Forest Insects is a revision of Ratze- 

 burg's great work, just as Escherich's work is a revision of Judeich and Nitsche's. 



Parasitic Insects 



According to Professor Trotter, the first person to divine the importance 

 of parasites and predaceous insects and to apply the principle successfully 

 was Boisgiraud of Poitiers, in France. About 1840, he freed the poplars in the 

 suburbs of his town of Gypsy Moth by placing the Calosoma sycophanta, 

 and he destroyed forficiilids in his own garden by using Staphylinus oleus. 



These successes seem to have inspired the Milanese to offer a m.edal to 

 be given in 1845 to any person who had in the meantime conducted successful 

 •experiments in the artificial breeding of carnivorous insects which may be 



