ENTOMOLOaiOA.L SOCIETY OF ONTARIO. 



77 



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

 to the trained entomologist. Few of the men practically onfjaged in agriculture and horti- 

 culture can follow the more or less technical characterizations of these beneficial species, 

 and where the discriminating knowledge is possessed, it can, as just intimated, only ex- 

 ceptionally 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 de- 

 scribing and illustrating such beneficial species. 



In other cases much good may be done without any special knowledge of the bene- 

 ficial forms, but as a result of a knowledge of a special fact which enables the farmer to 

 materially encourage the multiplication 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 



Fig. 36. 



Fig. 35. 



cases attached to twigs, is a case in point. (Fig. 35, a and b, represents the curious 

 cases made by these worms ; c, the head of a larva ; d, the moth. Fig. 36, shows a case 

 covered with a bunch of withered leaves.) Many years ago I urged the importance of 

 preserving the several 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. . . . V/hether col- 

 lected 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 centre of a meadow or field away from any fruit trees. Here the worms 

 will wander about a few jards and soon die from exhaustion and \\ant of food, while such of the parasites, 

 hereafter mentioned, as are developed or in the pupa state will mature and eventually fliy off. In this 

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



The practical value of this suggestion was subsequently fully demonstrated, and 

 especially by the late D. B. Weir, who, at a meeting of the Illinois Horticultural Society, 

 as secretary of a committee appointed by said society to consider the best means of secur- 

 ing co-operation in the warfare against the fruit-growers' insect enemies, announced that 

 this policy had been followed with happy results. 



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



