AMERICAN ECONOMIC ENTOMOLOGY 215 



spaces ; and it is this closing-up process which proves fatal to a 

 certain percentage of the weevil-grubs, as well as to pupae and 

 adult beetles. 



" It seems safe to conclude," runs the text of the Bulletin of 

 1906, "that the great majority of deaths due to proliferation may 

 be caused by the mechanical effect of the formation in first 

 enveloping the larva so closely as to prevent its movement, and 

 then the continued formation producing sufficient internal 

 pressure slowly but surely to crush to death the foe whose 

 attack has called forth this effort at self-defence on the part of 

 the plant. Such an explanation alone accords with the facts as 

 we know them. These observations present to us in a very 

 vivid way an illustration of the intensity of the struggle going 

 on between plant and insect life. It is a life-and-death struggle, 

 and it is not always the insect that wins," especially, it is added 

 elsewhere, when man is on the side of the plant. 



On an average, it is believed that proliferation leads to the 

 death of about 13 per cent, of the weevils. In some cases, 

 however, the percentage rises as high as 30 per cent. ; and it 

 will be obvious that great advantage would attend the cultiva- 

 tion of strains of cotton which naturally exhibit a strong 

 tendency to proliferate, or which can be made to do so under 

 the influence of artificial stimulants. 



To quote once more from the Bulletin of 1906, the following 

 statement with regard to the actual value of proliferation in 

 keeping the boll-weevil under control will be read with interest : 



" From a comparison of the results obtained it was hoped 

 that some factors might be found which could be used practically 

 in increasing proliferation, and thus rendering it more effective 

 as a factor in controlling the weevil. In many cases the results 

 of the work have been quite different from those anticipated, but 

 enough has been learned to justify the assertion that at present 

 proliferation is a more important factor in retarding the multi- 

 plication of the weevil than are the parasites which have thus 

 far been found." 



The moral of the whole problem is that the most likely 

 methods of keeping the pest under control will be found to 

 consist in a judicious combination of influences inimical to the 

 development of the weevil with those favouring the improvement 

 of the cotton-crop itself. 



Even this, however, does not exhaust the case of the cotton- 



