13 



ical soils are detailed on a later page. Owing to complications which 

 would result from the presence of the weevil, these experimental farms 

 were as much as possible located in sections comparatively free from 

 this pest in Texas. 



One feature of the work has been the comparison of varieties of 

 cotton with especial reference to their earliness, prolilicness, and 

 quality of staple. In all, 75 supposed varieties of cotton have been 

 compared during the past year. 



In the case of insects attacking staple crops, the mai'gin of profit in 

 their cultivation does not often permit of the employment of remedial 

 measures other than those involving changes or improvements in farm 

 practice. However, the readiness with which cotton may be poisoned 

 with Paris green or other arsenicals, particularly in a dry form, by 

 means of poison blowers or the primitive but effective method of bags 

 suspended from poles, has placed this operation among those which 

 ma}' reasona])ly be employed. Considerable attention has been given 

 to the matter of testing poisons in bollworm control, both in 1903 and 

 1904. In all cases the plan has been to measure off, say, 20 acres of 

 uniform cotton, 10 of which Avould be poisoned and 10 left as a check. 

 The efficacy of the treatment has been measured by the 3'ield from the 

 respective areas. 



No rational plan may be formulated for the control of an insect 

 except as based on a thorough knowledge of its life and habits. The 

 importance of life-history studies is therefore evident. The labora- 

 tory investigations of the past two years have covered all important 

 features of the biology of the bollworm, confirming many points 

 already known and enlarging our knowledge of the species. The 

 determination of the number of generations was effected by the use of 

 a large breeding cage in which corn and cotton were grown exactl}^ 

 as in the fields. These observations were checked by rearing experi- 

 ments in the laboratory. The destructive capacit}^ of individual boll- 

 worms was determined repeatedly by confining a larva on a cotton 

 plant under a wire cage. The efficacy of poisons was determined in a 

 small way by the same plan. The effect of the destruction of pupal 

 cells, as would be accomplished by plowing, was determined ])oth for 

 low and high temperatures. The length of life cycle and the number 

 of stages has been determined for a large series of individuals cover- 

 ing the entire season. The effect of food on the life and egg laying of 

 the moth, the number of eggs deposited b}^ a single female, conditions 

 which affect their vitalit}', and many other points have been investigated. 



Especial attention has been given to the study of the parasites and 

 predaceous enemies of the bollworm, especially as to their value in 

 keeping this pest in subjection. Ifr has always been a pleasing propo- 

 sition to import from foreign countries the enemies of a pest and array 

 these against it in the hope of lessening its destructiveness. Early in 

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