162 Bulletin Wisconsin National History Society. [Vol. 9, No. 4. 



of them, are widely distributed and general feeders, in them- 

 selves adaptive and successful animals. Of these, the browntail 

 moth, the bollworm, the cabbage worm and the codling moth are 

 examples ; all of these have a high reproductive rate and furnish 

 a large excess of progeny which must be destroyed for their own 

 welfare and which are available as food for this parasite. 



From the standpoint of a single locality, fluctuations must of- 

 ten occur; a host, such as one of the four mentioned, through 

 favorable conditions may become excessively abundant ; this para- 

 site may then concentrate its attack upon it and for the time being 

 and in that particular place practically reduce its numbers to zero 

 or even annihilate it without suffering any decrease in numbers 

 itself. This is possible in theory but not too probable as there is 

 still the tendency to be impartial to most of its hosts which must 

 be overcome. Something of this kind must happen frequently in 

 Texas in the case of the bollworm not carried to extremes, how- 

 ever, but seemingly destroying the large excess of individuals of 

 the species which had been reproduced up to the danger point 

 for the species ; the parasite then goes to one of its other hosts 

 such as Alabama and thus enabled to keep up average rate of re- 

 production, after it has exhausted the supply of food afforded by 

 the first. That in the end its attacks are beneficial to a host which 

 has thus increased immoderately, paradoxical though it may 

 seem, must be conceded, else in the end it must perish itself or 

 lose greatly in numbers. For its own welfare, then, its must be 

 concerned for the welfare of its hosts or group of hosts. This 

 parasite has no animal enemies and is preyed upon consciously 

 by no other organism. Thus the only organic check which it 

 meets with directly is this factor of the welfare of its hosts taking 

 them as a unit ; in other words, the abundance of its food supply. 

 Indirectly, I do not know of any organic unit which affects it for 



