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 epliemerceformis). 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 contained in the female bag, may perish, while the parasites 
develop and escape. Prof. J. H. Gomstock has suggested in a similar 
way the placing of the hand-collected chrysalides of the imported Cab- 
bage Worm (Pieris ra/pce) in boxes covered with wire netting, in order 
to admit of the ready escape of the little Ohalcid 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 
Eev. 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 
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 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, m 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., Sigalphus curculionis Fitch and Pori- 
zon conotracheli Eiley to several correspondents in other parts of the 
State. I also urged a similar course with regard to some of the para- 
sites of the Coccidse, which it happens may be easily transported from 
