WHOLE VOL. APPLIED ENTOMOLOGY HOWARD 499 



to discover the real nature of this phenomenon and to reahze the exis- 

 tence of true parasitic insects. Reaumur and De Geer, those great stu- 

 dents of the life histories of living insects, worked out the biology of a 

 number of parasites ; and in the last quarter of the eighteenth century 

 and the first half of the nineteenth many descriptive works on para- 

 sites were published. 



An early significant suggestion was made by the German writer, 

 G. L. Hartig, who in 1827, in a paper giving instructions for the 

 destruction of " kienraupen," recommended the construction of large 

 rearing cages for parasitized caterpillars in order to rear the para- 

 sites in large quantities to be liberated later. 



One of the first writers to call especial attention to the great value 

 of parasitic insects to man was Ratzeburg, since he added to his great 

 work on forest insects a large volume on the parasites of forest 

 insects (Die Ichneumonen der Forstinsekten). While he thoroughly 

 understood the part played by parasites in the control of forest in- 

 sects, he did not believe that this control could be hastened by man. 



An early bit of practical work was done by Boisgiraud of France, 

 who in 1840 collected numbers of the Carabid beetle, Calosoma syco- 

 phanta, and placed them upon poplars along a road in Poitiers, where 

 they destroyed the caterpillars of the gipsy moth. The same observer 

 destroyed earwigs in his own garden by placing with them a preda- 

 tory rove beetle {Staphylinus oletis). 



The work of Rondani in Italy, a systematic writer on parasitic 

 insects, was important, since it contained tables giving the host rela- 

 tions of different species. His work was published between 1840 and 

 i860. Silvestri has called attention to the fact that, in the dispute 

 which sprang up in Italy about 1868 as to the usefulness of insec- 

 tivorous birds to agriculture, Dr. T. Bellenghi was referring to Ron- 

 dani when he spoke in 1872 the prophetic words '* Entomological 

 parasitism has a future, and in it more than in anything else Italian 

 agriculture must put its faith." 



Several authors between 1872 and 1882 made practical suggestions 

 as to several ways of permitting the escape of parasitic insects before 

 the destruction of their hosts, notably Riley in the case of the rascal 

 leaf-crumpler {Mineola indigenella) ; the French writer, F. Decaux, 

 in regard to the parasites of the apple bud weevil ; Comstock with the 

 parasites of the imported cabbage worm ; Riley with the bag-worm, 

 and later Berlese and Silvestri in Italy and Marchal in France. 



Suggestions were made regarding the transfer of parasites from 

 one part of a given country to another part of the same country, by 

 LeBaron in 1872, Decaux in the same year, by Riley in 1870, and by 



