HIBEENATIOIT AND DEVELOPMENT OF BOLL WEEVIL. 31 



It is frequently asserted that frequent cultivation is of value against 

 the weevil in that the immature stages are killed b}^ covering the 

 squares with soil. The data given in Table VI hardly confirm this. 

 Rarely will squares be buried over 1 or 2 inches. Lots 1, 2, 3, 4, 5, 

 9, and 10 show that the mortality in squares buried at this depth is 

 about the same as under normal conditions. Lots 6 and 7 seem to show 

 a benefit from burial, but these were placed in rather dry soil in the 

 field in open sun, and when compared with lots A and B on the sur- 

 face it is seen that the burying insured a greater per cent developing. 

 It seems safe to say that in no case will burial for not over 2 inches 

 result in any great mortality, and that in all probability the percent- 

 age of weevils developing will be greater than if left exposed to the 

 sun on the surface. It is more frequently claimed that by plowing 

 squares under deeply after a good rain the moist soil will rot them 

 and the weevils will be unable to escape. Unfortunately we have 

 no conclusive tests upon this point, but it would seem that a suffi- 

 ciently deep plowing to bury squares 4 inches just after a rain would 

 be such a decidedly bad agricultural practise as to possibly offset any 

 benefit that might be derived from destroying the weevils in the 

 squares buried. 



RATE OF INCREASE OF THE WEEVIL. 



Hunter and Hinds have shown that a female weevil normally lays 

 some 150 eggs during an average of about 51 days, and that nearly 

 one-half of the eggs are deposited during the first third of the period 

 of oviposition. Allowing 24 days for the development of the average 

 adult and 18 days for the oviposition of one-half of the eggs, they also 

 estimate that the average length of a generation is about 12 days. 

 The sexes of the weevil are produced in about equal numbers. With 

 these factors as a basis we may easily compute that if on June 1 there 

 were an average of 2 weevils to 100 stalks of cotton, on eluly 15, at the 

 end of the first theoretical brood, there would be 50 weevils; and that, 

 if one-half of these were females and the usual percentage survived, 

 on September 1 there would be 1,250 weevils to 100 stalks. But these 

 computations make no allowance for the mortality in the immature 

 stages, and extended observations in the field show that such rapid multi- 

 plication does not really occur. It has been ascertained by the writer 

 that the first brood of weevils rarely numbers more than five times the 

 hibernated brood, and at College Station often but two or three times. 

 At Vienna, in 1903, Mr. Teltschick picked 211 weevils from his trap 

 rows up to June 1, while on June 1 to T, 15, and 22 he picked 759 weevils 

 on the same area. This doubtless represents very accuratel}^ the increase 

 of the first brood over the hibernated weevils, showing an increase of 315 

 per cent. It is of course probable that some weevils had left the trap 

 rows for the planted cotton, which was barely commencing to square 



