16 BULLETIN 344, U. S. DEPARTMENT OF AGRICULTURE. 



DEVELOPMENTAL PERIOD. 



IN COTTON SQUARES. 



No observations were made on the length of the different immature 

 stages in cotton squares, but the total developmental period was 

 studied throughout the season from eggs deposited from July 6 to 

 about the 1st of November. The squares were placed on moist sand 

 in glass tumblers each day and the sand was kept damp. The date 

 of the emergence of the adult was noted and the period between egg 

 deposition and adult emergence was thus determined. However, 

 this period was often not a true developmental period because it was 

 found that, instead of emerging within a day or two after transform- 

 ing to adult, as is the case with grandis in the Southern States, many 

 of the weevils would remain in the cells for some days after becoming 

 adult. This was particularly the case during the latter part of the 

 season. 



In watching for the emergence of adults each lot of squares was 

 examined daily for about 20 days after egg deposition and then was 

 examined only occasionally. In this way the dates of emergence 

 were secured when the weevils emerged shortly after becoming 

 adults, but late in the season many emerged after the daily observa- 

 tions had been stopped and consequently no figures were secured on 

 their time of emergence. As this delayed emergence did not become 

 usual with the weevils until those from eggs deposited after the 1st 

 of September had developed, the data have been divided at this date 

 and are given in Tables V and VI. 



The figures in Table V are probably very nearly those for a develop- 

 mental period such as is experienced by the Texas cotton boll weevils 

 and the periods are surprisingly similar to those of cotton boll weevils. 

 It is interesting to note that the average developmental period of 

 both sexes of iJiurberiae in Arizona was 15.4 days while in southern 

 Texas it was 18.5 days. It seems probable that nearly all of the 

 weevils included in Table VI delayed emergence. This was probably 

 due to the approach of the time for entering hibernation. From the 

 squares receiving eggs before September 1, 71 weevils emerged in 

 normal time and 2 were retarded, while from those receiving eggs 

 after this date 10 emerged more or less normally and 48 were retarded. 



In this series 1,260 squares containing eggs were observed and 

 these produced 145 weevils, including those found in the cells. In 

 other words, only 11.5 per cent of the squares receiving eggs pro- 

 duced adults. This is a very low percentage and seems to indicate 

 that the cotton squares are not completely suited to the development 

 of the Arizona weevil. 



