BIOLOGY OF ARIZONA WILD COTTON WEEVIL. 15 



relation to cotton bolls and squares. These all gave the same result, 

 namely, that cotton bolls were much preferred to cotton squares. 

 While thore would always be some feeding upon the squares and an 

 occasional egg would be deposited in them, by far the greater part 

 of the feeding and deposition was on the bolls. In the field experi- 

 ments where the weevils were placed on growing cotton plants there 

 was some feeding on squares but the bolls received almost all of the 

 feeding and deposition. In the breeding experiments where weevils 

 were mated on squares for some time and then placed on bolls the 

 oviposition continued through the change of food without diminution. 

 In view of these observations it seems quite reasonable to believe that 

 the cotton bolls are better suited to the weevil than the squares and 

 hence it is hard to account for the much lower fecundity shown by 

 the weevils in this boll-fed series than by those in the corresponding 

 series fed upon squares. 



WEEVILS FED ON THURBERIA. 



At different times during the season weevils were removed from 

 their hibernation cells in Thurberia bolls and mated in glass tumblers 

 containing Thurberia leaves, squares, and bolls. For some reason 

 these attempts to secure egg deposition were almost total failures. 

 Nine pairs were mated in this manner and of these, seven females 

 failed to deposit any eggs, one deposited a single egg, and the other 

 deposited 66 eggs. This last female was placed with the food Sep- 

 tember 1, deposited the first egg September 23, and the last October 

 16, giving an oviposition period of 24 days. The average number of 

 eggs per day was 2.7. 



Some of the females which did not oviposit were allowed to live until 

 their normal death, while others were killed after some weeks because 

 of lack of food. It is difficult to determine the cause of this failure 

 of the females to oviposit, but it is probably due to some fault in the 

 breeding methods. One point which was noted in this connection 

 was the extreme rapidity with which Thurberia bolls ripen after 

 removal from the plant and hence become unfit for egg deposition. 

 The seeds dry and harden very rapidly even though the boll is quite 

 small. In such bolls the weevils will feed through the tender tissue 

 near the stem end, but will not oviposit. The experimental conditions 

 (cages, tumblers, etc.) were exactly the same as those for weevils 

 upon cotton squares and bolls which were ovipositing normally at 

 this same time, so the cause evidently was some fault with the con- 

 dition of the food. Two females which were allowed to remain in 

 tumblers with Thurberia bolls and squares for 14 days without 

 oviposition were then transferred to living Thurberia plants in the 

 field and they immediately began ovipositing. 



