PROCEEDINGS OF THE THIED ENTOMOLOGICAL MEETING 483 



Pink Bollworm. Briefly described, the material for investigation 

 consists of fixed numbers of green bolls taken weekly in all the pro- 

 vinces and sent in for examination. It is desired that the bolls from 

 any province shall not all come from one field nor from a single village. 

 This scattering of the samples is intended to improve the sampling 

 for each province. No fear need be entertained of individual bias being 

 introduced by the collectors, as it is impossible to judge whether green 

 bolls are sound or attacked, without cutting them open. 



In the Laboratory these bolls are shced through, each in at least 

 three places, and examined for larvae. All bolls received from any 

 province between Friday and Thursday are reckoned together as 

 belonging to the week commencing on the Friday. The samples (about 

 1,000 bolls for each province) are worked up in batches of 100 bolls for 

 convenience in finding percentages and for probable-error calculations 

 should such be required. Each operator examines his 100 bolls ; when 

 finished the supervisor checks the work ; thus not much error creeps 

 through. 



As a result of these examinations we can now give certain general 

 results, and indicate anticipated ones which will probably be gained 

 when we have a sufficient number of years' work behind us to allow 

 average figures to be made. 



The seasonal distribution is very marked. Every year we commence 

 in the Delta in July with only a few per cent, of the bolls infested. The 

 degree of infestation progresses slowly but steadily until about one 

 quarter of the green bolls are attacked. Then the position changes 

 rapidly ; for any small locality about three weeks suffice, for any 

 province or for the Delta four or five weeks will find 75 per cent, and 

 more of the bolls attacked. The end is always the same, provided 

 the bolls are collected late enough in the season, namely 90 to 100 per 

 cent, infestation. 



What the croji will be depends on the period when the 25 per cent, 

 infestation average is reached. If this point is reached early, as 

 compared to the maturity of the crop, the result will be a disaster ; if 

 late, it will mean a good crop. 



Now, 100 per cent, infestation at the end of the season sounds 

 serious, but the gravity is more apparent than real. The green bolls 

 at the end of the season will not ripen in any case, and are consequently 

 of no importance except as preparing the next year's crop of worms. 

 And this leads to the next consideration, the greatest crop of worms 

 in green bolls is not at the period when the percentage of attack is 

 highest, but at an earlier period when the green boll population ia 

 greater. The sudden rise in the percentage of attack from 25 per cent. 



