26 



BULLETIN 926, U. S. DEPARTMENT OE AGRICULTURE. 



The 551 weevils bred under field conditions from squares of all 

 three types of cotton required a total of 12,012 weevil days or an 

 average period of development of 21.8 days from egg to adult. 



The average developmental period of the weevil in all three types 

 of cotton squares under insectary conditions is shown in Table XIII 

 to be 14.3 days from egg to adult. The average developmental 

 period under normal field conditions for weevils bred from all three 

 types of squares is shown to be 21.8 days. Under actual field condi- 

 tions it is safe to say the boll weevil requires a period of 7.5 days 

 additional time for development, or fully one-half more time than is 

 required under insectary conditions at Madison, Fla. 



Table XIII.- 



■Table showing the developmental period of the boll weevil under 

 insectary conditions, 1919. 



Nature of vecvils. 



Larvalfood. 



Period of ovi- 

 position. 



o . 



c- .- 

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 ft 

 CD 



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 M 



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 > 



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 %£ 



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 fa 



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 _o 

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 60 

 03 

 « 



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 < 



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 b CD 

 CD fn 



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 Eh 



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 CD 



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 03 



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 CD 

 > 



Hibernated 



Upland cot- 



June 5-July 25 



247 



3,692 



Days 

 14,9 



123 



1 816 



Days 

 14.7 



370 



5,508 



Days 

 14.8 





ton squares. 



July 5-Aug. 19 



189 



2,765 



14.6 



117 



1,762 



14.3 



306 



4,438 



14.5 









Total upland 

 cotton. 

 Long-staple cotton : 

 First generation. . . 



436 

 210 



6,457 

 2,953 



14.8 

 14.06 



240 

 154 



3,578 



2,187 



14.5 

 14.2 



676 

 364 



9,946 

 5,140 



14.7 



Long-staple 



July 9-Aug. 2 



14.1 



Sea-island cotton. 



First generation . . . 



squares. 



Sea-i s 1 a n d 

 squares. 



July 5-Aug. 9 



67 



917 



13.6 



41 



565 



13.7 



108 



1,482 



13.7 





713 



10, 327 



14.15 



435 



6,330 



14.1 



1,148 



16,568 



14 3 











Table XIV. — Shotting the total developmental period of the boll weevil under 



field conditions. 



Nature of weevils. 



Larvalfood, 



Upland cottoti: 



Hibernated Cotton sq... 



I". do 



First generation do 



Second generation do 



Total upland 



fni ton. 

 nil cotton: 



generation . Cotton sq... 

 otton: 

 i ir * generation do 



Period of ovi- 

 position. 



May29-.Tunpl3. 



lime 22. 



July 3-Aug. 2.. 



July 31- An.-. 22 



Total ;ill three 

 f cotton, 



Juno 28-Aug. 1 

 June30-July30, 



Males. 



•« a 



o -o 



36 



92 

 35 

 807 



L536 



477 



1, 344 



639 



3, 896 



2,006 

 720 



0,11'JS 



Females. 



Days 

 20. 9 



20.7 



22 



23.4 



21.7 143 



21.8 7.", 

 20. 7 26 



1, 145 



007 

 718 

 714 



3,184 



1,651 

 549 



21.4 244 5,384 



Dai/s 

 22. 01 

 22.5 

 21.8 

 23.03 



22.33 



22 

 21.8 



Both sexes. 



1 25 

 50 

 94 

 54 



323 



167 

 61 

 551 



2, 681 

 1,084 

 2, 002 

 1,253 



7,080 



tea 



03+; 



CD.O 

 < 



Day? 

 20)8 

 21.6 

 21.9 

 23.2 



21.9 



3,657 21.9 

 1,275 20.9 



12,012 21.8 



