14 



obtained by calculation for the previous week, minus the bolls matured 

 during the week. 



On the diagram the average number of bolls per thousand plants, 

 obtained in the manner just described, has been plotted in, and connected 

 by the upper curve, the lower curve shows the number of the bolls 

 present containing Gelechia larvae calculated from the percentage given 

 in Table III. These two curves are representative of the conditions in 

 the Delta and Middle Egypt. (See also Table IX.) 



Before drawing any conclusions, it may be permitted to draw 

 attention to the remarkably smooth curve obtained, not only for 

 green bolls, but also for bolls attacked by Gelechia. In the opinion 

 of the author this fact seems to justify the hope that as approximation 

 the green boll curve does not exhibit any great error and that the 

 following conclusions may be considered as approaching the truth. 



During July the Gelechia population remained fairly level. 



The infestation in July was probably due mostly to the progeny 

 of Gelechia moths which had survived from the year before as hiber- 

 nating larva; (see Table X). In August the new short generation 

 insects made themselves evident, with the result that the available 

 food supply became more and more completely occupied by Gelechia 

 larvae. The increase in actual numbers, as well as in percentage of 

 available bolls attacked, when once commenced, went forward at a very 

 uniform rate, showing that breeding was continuous and unchecked, 

 and that Gelechia does not produce distinct broods, separated by 

 intervals of time in the same way as Prodenia or other well known 

 lepidopterous cotton pests. 



Although the highest percentage of bolls attacked was found in 

 the second week of October, the largest number of bolls attacked 

 must have existed during the third week of September. If the 

 figures on which our calculations have been based are accepted as 

 sufficiently accurate, it can be estimated that when at its maximum the 

 Gelechia population reached at least 4,500 individuals per thousand cotton 

 plants (500 holes). Supposing 26,000 plants to the feddan, this gives 

 the alarming total of about 120,000 worms to the feddan. 



On Tables XI, XII, XIII, the percentage for Earias by Markaz, 

 by Mudiria, and by larger units of space, have been recorded in a similar 

 manner. 



