132 



The practical value of this suggestion was subsequently fully dem- 

 onstrated, and especially by the late D. B. Wier. who, at a meeting of 

 the Illinois Horticultural Society, as secretary of a committee appointed 

 by said society to consider the best means of securing cooperation in 

 the warfare against the fruit-growers' insect enemies, announced that 

 this policy had been followed with happy results. 



A similar course was urged by me in the case of our common Bag- 

 worm (Thyridopteryx ephemercvformis). This species, as we know, is 

 also subject to parasites, and the bags or cases which are collected in 

 winter, instead of being burned, should be allowed to remain until the 

 middle of the next summer in some vessel well separated from trees and 

 shrubs, in order that the young worms, when they hatch in spring from 

 the eggs contain d in the female bag, may perish, while the parasites 

 develop and escape. Prof. J. H. Comstock has suggested in a similar 

 way the placing of the hand-collected chrysalides of the imported Cab- 

 bage Worm (Pieris rupee) in boxes covered with wire netting, in order 

 to admit of the ready escape of the little (Jhalcid parasite (Pteromalus 

 puparum) and at the same time retain such of the butterflies as may 

 issue a practice which had, I believe, been successfully employed in 

 Europe. Other similar cases of this mode of encouragement will occur 

 to you, but, as already stated, with comparatively few exceptions, such 

 as those indicated, the multiplication of our parasitic and predaceous 

 species on the line of the first method is practically beyond our control. 



It is quite different in the second method of dealing with beneficial 

 insects, for here man has an opportunity of doing some very effective 

 work, and it is only within comparatively recent years that the impor- 

 tance of this particular phase of the subject has been fully realized. The 

 Rev. C. J. S. Bethune, of Canada, was probably the first entomologist 

 to suggest, in one of the earlier volumes of the Canadian Farmer, the 

 importation of the European parasites of the Wheat Midge (Diplosis 

 t t-it id) into America, on the supposition that this cosmopolitan species 

 might thus be kept in check on this continent to the same extent that 

 it was in Europe. So far as I am aware, the attempt was never 

 actually made, and though some subsequent correspondence was 

 entered into between Fitch and Curtis, and later between Walsh and 

 some of his English friends, nothing tangible resulted. The matter 

 was, in fact, never seriously studied with this purpose in view. 



The importance of this phase of the subject was early forced upon my 

 attention, as it was upon that of others, and is frequently referred to in 

 my earlier writings. Thus, in 1869-'70, in studying the parasites of the 

 Plum Curculio, it became evident that they were of such a nature that 

 they could easily be transported from one locality to another, and I 

 distributed from Kirkwood, Mo., Siyalphus curculionis Fitch and Pori- 

 zon conotraeheli Kiley to several correspondents in other parts of the 

 State. 1 also urged a similar course with regard to some of the para- 

 sites of the Coccidie, which it happens may be easily transported from 



