131 



was an active, wrngeVl mature, capable of extended flight, lie con- 

 cluded that remedial work was useless, since the flies could, and doubt- 

 less -would, deposit their eggs over the entire surrounding country. 

 As a consequence the worms were allowed to travel to the adjoining 

 fields and the injury thus increased through ignorance of the fact that 

 the Tachina flies were the most important of the parasitic enemies of 

 the worm. For many years well-informed gardejiers in parts of Europe 

 have practiced collecting ladybirds and some of the ground beetles to 

 liberate upon plants infested by plant-lice or by cutworms. The char- 

 acteristics of these two families, Coccinellidae and' Carabidse, should be 

 taught in our schools, as a definite knowledge of certain species, which 

 is readily acquired, may often be turned to account in a limited way by 

 the cultivator. 



In a few cases like this there is no reason why the farmer should not 

 be taught with advantage to discriminate between his friends and his 

 foes, and to encourage the multiplication of the former; but for the 

 most part the nicer discriminations as to the beneficial species, some 

 of the most important of which are microscopically small, must be left 

 to the trained entomologist. Few of the men practically engaged in 

 agriculture and horticulture can follow the more or less technical 

 characterizations of these beneficial species, and where the discrimi- 

 nating knowledge is possessed it can, as just intimated, only excep- 

 tionally be turned to practical account. Thus our literature on this 

 subject in the past has been of interest from the entomological rather 

 than from the agricultural point of view, as most writers on economic 

 entomology have contented themselves with describing and illustrating 

 such beneficial species. 



In other cases much good may be done without any special knowl- 

 edge of the beneficial forms, but as a result of a knowledge of the 

 special facts which enables the farmer to materially encourage the mul- 

 tiplication of parasitic species while destroying the plant- feeding host. 



The Rascal Leaf-crumpler (Mineola indiginella Z.), a common insect 

 which disfigures and does much damage to our apple and other fruit 

 trees and which hibernates in cases attached to twigs, is a case in 

 point. Many years ago I urged the importance of preserving the sev- 

 eral parasites known to prey upon it, in the following language:* 



The orchardist has but to bear in mind that it (the leaf-crumpler) is single- 

 brooded and that it passes the winter in its case, and he will understand that by 

 collecting and destroying these cases in the dead of the year when the tree is bare, 

 he effectually puts a stop to its increase. * * * Whether collected in winter or 

 pulled off the trees in spring or summer, these cases should always be thrown into 

 some small vessel and deposited in the center of a meadow or field away from any 

 fruit trees. Here the worms will wander about a few yards and soon die from 

 exhaustion and want of food, while such of the parasites, hereafter mentioned, as 

 are developed or in the pupa state will mature and eventually fly off. In this 

 manner, as did Spartacus of old, we swell the ranks of our friends while defeating 

 our foes. 



*Fourth Report, Insects of Missouri, 1871, p. 40. 



