16 



BULLETIN 926, U. S. DEPARTMENT OF AGRICULTURE. 



normally, merely being weighted by a light string tag. When the 

 infested squares fell the date was recorded on the tag. All of the 

 infested squares of a certain weevil were assembled in an inclosed 

 area to prevent damage (fig. T) and placed on the soil under the 

 plant just as they would normally lie. They were watched daily, 



and only about two 

 days before emergence 

 was expected were 

 covered, still under 

 the plant, by coarse 

 wire screen cages (fig. 

 7) in order to get the 

 number of weevils 

 that emerged and 

 determine the sex. 

 Hence abnormal con- 

 ditions were experi- 

 enced for only about 

 2 days. 



Since these records 

 indicated a much 

 longer developmental 

 period than was re- 

 corded in previous 

 bulletins, a complete 

 series of control ex- 

 periments was con- 

 ducted in the outdoor 

 insectary (fig. 8). 



It will be seen by 

 Table VIII that the 

 developmental period 

 in the tumblers under insectary conditions at Madison is much more 

 rapid than under the most favorable outdoor conditions experienced. 



Table VIII. — Showing the length of the developmental period of the boll 

 weevil under insectary and field conditions, Madison, Fla., 1918. 



Fig. 6.— The infested squares tagged on the cotton plant, 

 Madison, Fla. 





In insectary, developmental 

 period. 



Outdoors, normal develop- 

 mental period. 



Aver- 

 age. 



Ten-day oviposition period. 



Num- 

 ber of 

 weevils 

 bred. 



Days. 



Num- 

 ber of 

 weevils 

 bred. 



Days. 



Accel- 

 eration 





Maxi- 

 mum. 



Mini- 

 mum. 



Aver- 

 age. 



Maxi- 

 mum. 



Mini- 

 mum. 



Aver- 

 age. 



of in- 

 sectary 

 days. 



June 4-13 



370 

 306 

 87 



15.6 

 15.2 

 18 



13.6 

 13.7 

 14.8 



14.8 

 14.5 

 15.8 



50 

 94 

 54 



24.5 

 24.2 

 24.3 



20.1 

 20.8 

 19.6 



21.6 

 21.9 

 23.2 



6.8 



July 3-13 



7.4 



July31-Aug. 9 



7.4 







