6 BULLETIN 233, U. S. DEPARTMENT OF AGRICULTURE. 



field to determine just what conditions are necessary to cause the 

 emergence of the adult. By combining the records secured under 

 both natural and artificial conditions it seems quite possible to 

 determine more or less definitely under what conditions the weevils 

 emerge, and by studying the seasonal climatology of the region 

 inhabited by the weevils we may know when to expect the appearance 

 of the adults. 



During the winter the boll containing the weevil cell passes through 

 a continual process of partial disintegration caused by alternate 

 moistening and drying. Following this, more or less moistening of 

 the weevil cell is necessary to allow emergence in most cases, although 

 an occasional individual emerges from time to time from the poorly 

 constructed cells. With this as a basis we need but study the dis- 

 tribution of the rainfall through the spring and summer months in 

 order to determine when emergence of the weevils is to be expected. 

 The temperature is undoubtedly usually high enough by the 1st of 

 April, and the emergence depends almost entirely upon the rainfall 

 from this time onward. April, May, and June are the dry months 

 in this locality, but a study of the seasonal precipitation for a num- 

 ber of years shows that even in the driest of years there are some 

 few light rains in this period and usually some precipitation each 

 month. So we may expect a scattering emergence of the weevil 

 throughout the spring and summer months, the extent of this emer- 

 gence depending upon the amount of the precipitation, and finally 

 culminating in the almost complete emergence following the heavy 

 rains of July and August. 



This very late emergence of the Thurberia weevils shortens the 

 breeding period in the greater part of the mountains to not over two 

 generations annually instead of the six to eight of the cotton weevils. 



It should be remembered that while this habit of hibernation anc 

 aestivation prevails in nature now, it is by no means certain that it 

 will be adhered to by the weevils in case they attack cultivated 

 cotton in the valley, but it appears likely to continue for some time 

 at least. Weevils reared on cotton in Arizona showed a very definite 

 adherence to this cell hibernation habit when bred in the bolls, but 

 it seems that they will emerge from the squares. Since the females 

 greatly prefer bolls for oviposition it seems probable that nearly aL 

 of the late-season breeding will be in these, and consequently little 

 emergence in the fall should be expected. In case the weevil adheres 

 to this cell hibernation habit the control should be quite simple, 

 entailing only the winter destruction of the plants and hibernating 

 weevils. 



Most of the breeding on the Thurberia plant seems to be in the 

 bolls, and under normal conditions the bolls from one-third to three- 

 fourths grown are selected for egg deposition. The eggs are placed 



