24 



BULLETIN 231, U. S. DEPARTMENT OF AGRICULTURE. 



IS THE FECUNDITY OF THE WEEVIL DECREASING? 



Iii previous bulletins on the boll weevil this question was put, but 

 not answered because of insufficient data. A comparison of the total 

 number of eggs laid by weevils at Victoria and the rate per day for 

 1902 to 1904 with 1913 gives the following results: 



In 1902 to 1904 at Victoria 132 weevils laid 11,863. eggs at the rate 

 of 89 eggs each, or 2.8 eggs each per day with a maximum of 135 eggs 

 per female. In 1913 at Victoria 19 weevils in various seasons laid 

 4,036 eggs at the rate of 212 eggs each, or 5.9 eggs each per day with 

 a maximum of 358 eggs. In one of the fecundity series in 1913 a 

 female grandis exceeded even this maximum and laid a total of 456 

 eggs. This evidence seems to indicate that if there has been any 

 change in the fecundity of the species it is in the nature of an increase 

 rather than a decrease. 



ovd?osition period. 



During the summer a total of 47 females were observed through 

 the complete oviposition period.. The results of these observations 

 are summarized in Table XV. 



Table XV. — Oviposition period of the boll weevil obtained in all experiments. 



Source of weevils. 



Season. 



Number 



of 

 females. 



Maximum 

 period. 



Minimum 

 period. 



Average 

 period. 



Once fertilized grandis females 



Grandis females with complete rec- 

 ord on copulation. 



June to September 



July to August 



5 

 9 



12 

 1 

 3 

 1 

 2 

 4 

 3 



2 



3 



2 



Days. 

 61 

 52 



55 



Days. 

 19 

 17 



12 



Days. 

 36 

 32.7 



33 8 







25 



Third generation grandis 



July to September 



August to September. . 

 do 



67 



16 



47.7 



Last of first generation grandis 



59 



44 

 34 



48 



49 

 52 

 38 



44 

 30 

 13 



27 



30 



29 



44 





September to October. 

 do 



32 



Positive crosses of male thurberise 



33 



and female grandis. 





38 



and female grandis. 

 Positive crosses of male grandis and 



female thurberise. 

 Doubtful crosses of male grandis 



September to October. 



39.3 

 33.5 



and female thurberise. 







Total 



47 

















35 8 









67 













12 















Here it is seen that the period ranged from 12 to 67 days with an 

 average of 35.8 days for all females. The number of females of the 

 different classes is too small to permit anything like an accurate 

 comparison of results. While the pure thurberise and the crosses 

 containing females of this variety averaged a slightly shorter time 

 for the period than the native grandis, this difference is not great 

 enough to indicate that there is any special significance in it. 



