78 



ENTOMOLOGICAL SOCIETY OF ONTAIIIO. 



A similar course was urged by me in the case of our common bag-worm {Thijri- 

 dopteryx ephemerceformis ) (Fig. 37.) This species, as we know, is also subject to para- 

 sites, 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 contained in the female bag, may perish, while the parasites develop and escape. 

 Prof. J. H. Conistock has suggested in a similar way the placing of the hand-collected 

 chrysalides of the imported Cabbage-worm (Pieris rapce) in boxes covered with wire 

 netting, in order to admit of the ready escape of the little Chalcid parasite (Peteromaliis 

 jniparum) 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 



Fig. 37. 



of encouragement will occur to you, but, as already stated, with comparatively few ex- 

 ceptions, 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 compara- 

 tively recent years that the importance of this particular phase of the subject has been 

 fully realized. The Rev. C. J. S. Bethune, of Canada, was probably the first entomol- 

 ogist to suggest, in one of the earlier volumes of the Canadian Farmer^ the importation 

 of the European parasites of the Wheat Midge ( Diplosis tritici) 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 ar 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 trasported from one locality to another, and I 

 distributed from Kirkwood, Mo., Sigalplnis curctdionis Fitch and Porizon conotracheli, 

 Riley, to several correspondents in other parts of the State. I also urged a similar course 

 with regard to some of the parasites of the Coccida3, which it happens may be easily trans- 

 ported from one place to another in their undeveloped or adolescent stages.* Le Baron, 

 in his studies of the Oyster-shell Bark-Louse of the Apple and one of its parasites 

 {Aphelinus mytilaspidis) tra-n^ytorted scale-covered twigs daring winter from Geneva, 111., 



* Third Rep., Ins. Mo., 1870, p. 29 ; Fifth Rep., do., 1873, p. 90. 



