ARIZONA WILD COTTON WEEVIL. 5 



LIFE HISTORY OF THE WEEVIL ON COTTON IN THE SOUTH. 



In order to understand the life cycle of the weevil it is well to review 

 briefly its action on cultivated cotton in the Southern States. The 

 female bores a small cavity in the square or boll and deposits the egg 

 in this, sealing the opening with a small gelatinous scale. The 

 egg hatches in a few days and the larva or "worm" feeds upon the 

 inner plant tissue. (Pis. Ill and IV.) After a period varying from a 

 few days to about two weeks the larva transforms to the pupa, a quies- 

 cent stage in which the first resemblance to the adult weevil is shown. 

 After a few days in this stage the pupa sheds its skin and becomes the 

 adult weevil, which quickly leaves the square or boll in which the 

 immature stages were passed and is soon ready to start the cycle 

 again. These immature stages usually require from two to three 

 weeks, although they vary with the temperature, food, and other 

 environmental factors. Starting in May or June and continuing 

 until September or October, as is the case in the cotton States, it 

 is quite possible for six or eight generations to be produced in a 

 single season, and as most' females deposit from 100 to 300 eggs or 

 more the progeny of a single pair may reach enormous numbers in 

 the course of a season. In fact, it has been conservatively estimated 

 that the annual progeny of a single pair of hibernated weevils would 

 reach 3,089,520. 



LIFE HISTORY OF THE WEEVIL ON THURBERIA. 



While the details of the life cycle of the Thurberia weevil in the 

 mountains in Arizona are much the same as those of the cotton 

 weevil in the South, there are a number of important differences. 

 Among them is the mode of hibernation, or manner in which the 

 winter is passed. 



Adults of the last fall generation of the cotton weevil usually 

 emerge from the squares or bolls in which they breed and seek shelter 

 in all kinds of situations offering protection near the cotton fields. 

 A great variety of crevices, trash, moss, and other shelters are used 

 for this purpose. The Thurberia weevil, on the other hand, fails to 

 emerge in the fall, but remains sealed up in a cell formed in the 

 nidst of the seeds in the boll and passes the winter in this condition, 

 xhen in the spring, instead of becoming active with the first warm 

 weather, as the cotton weevil does, the greater number of them 

 remain sealed in the cell until the rains late in the summer, many 

 not emerging until August. This is simply a case of prolonging the 

 period of hibernation into one of aestivation, a habit often observed 

 among species living in arid regions. In order to know when to 

 expect the weevils, a number of experiments have been conducted 

 in the laboratory and close observations have been made in the 



