and become much greater, than when the tolerance is great. Table ITI 

 has been prepared to show the number of worms required to produce 

 infection for true percentages from 3 per cent to 99 per cent at 

 intervals of 3 per cent, when the tolerance is unlimited, or ten, eight 

 or six worms. 



It will be observed that the number of worms likely to be present 

 is greatly influenced by the limit of tolerance of the bolls. 



The total number of worms required to produce 99 per cent 

 attack, if there is no top limit of numbers of worms per boll would be 

 about 9,900. This involves certain bolls containing more than 100 

 worms, and is obviously not possible of occurring. 



The number of worms required to give the same percentage 

 damage, when the largest number present in a single boll is limited to 

 ten, eight or six are about nine hundred and fifty, seven hundred and 

 seventy and five hundred and eighty. It will be remarked that the 

 numbers at the commencement of the table are the same for all four 

 columns, and that the rate of rise of the number of worms required 

 is at first slow, becoming more and more rapid as the higher percentages 

 are reached. It is most important to remember that increases in 

 percentages of infestation obviously mean more in numbers of worms 

 present at the upper end of the scale than at the lower. Just how- 

 much the difference really is will depend on the average limit of 

 tolerance. For this reason the numbers required for six, eight and 

 ten worms have been calculated and tabulated here. It may, however 

 be remarked that the probability is that six is too low a figure to take, 

 and that eight or ten are much more probable. Ten and even twelve 

 worms in one boll have actually been observed on more than one 

 occasion. 



The actual number probably depends to some extent on the 

 variety of cotton that is being attacked. The material, on which this 

 paper is based, is almost exclusively Sakellarides, which produces on an 

 average about fifteen or sixteen seeds per boll. It is obvious that thetop 

 limit of numbers of worms per boll will vary according to the number 

 and weight of the seed produced. A variety producing more seeds 

 will tolerate more worms, given seeds of equal average weight. Or a 

 variety producing heavier seed might tolerate more worms, even 

 though producing only the same number of seeds. Pink boll worms 

 most frequently (not always) occupy or attack two seeds, though o; o 

 or three seeds may be required. If each worm used two seeds, eight 

 worms would be the limit in a boll containing sixteen seeds. Eight, 

 nine or ten worms are likely to be the limit, something also depending 

 on the age of the boll when attacked. For the further purposes of this 

 paper the exact number is not material. 



