112 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



rested for some time, as it appeared impossible to ascertain the 

 variable elements. 



A very recent study of the data on the .development of the 

 weevil brought out the fact that instead of there being only 

 one factor in the development, there were several factors. 



Observations of the egg stage at different localities in differ- 

 ent months, but with a mean temperature within 1 degree of 

 80 degrees, gave a considerable variation in the length of the 

 stage. At Alexandria, Louisiana, the incubation period was 

 1.9 days; at Tallulah, Louisiana, 2. 6 days; at Victoria, Texas, 

 3.73 days; and at Dallas, Texas, 4.1 days; these differences 

 corresponding quite regularly to the differences in the amount 

 of humidity of the various places. The same differences have 

 been found in the studies of the larval and pupal stages, so 

 that it is quite apparent that the relative humidity at a given 

 temperature is a controlling factor. It is impossible to state 

 any particular formula for this control by humidity, but it 

 may be said with truth that the length of the developmental 

 period increases as the mean humidity decreases. 



It is of course well known that the developmental period is 

 greatly influenced by temperature. At Victoria, Texas, it 

 was found that the egg period varied from 3.73 days at 81 

 degrees temperature to 13.9 days at 62 degrees. In like man- 

 ner the larval stage at Victoria varied from 7.5 days at 78.7 

 degrees to 25 days at 62.5 degrees, and the pupal stage varied 

 from 3.5 days at 82.65 degrees to 14 days at 61.55 degrees. 

 These same variations in accord with the variations in the 

 temperature have been found for all of the other places ex- 

 amined, but it is also impossible to give a definite formula for 

 this variation, because it is impossible to carry on observations 

 with temperature as the only variant. To give a formula, it 

 would be necessary to include both humidity and temperature. 



It was not thought that any other factor was likely to have 

 a controlling influence in the development of the weevil, but 

 Mr. Cushman, in his studies at Tallulah, Louisiana, in 1910, 

 in which he had his squares under more or less even climatic 

 conditions, found that 475 males averaged in development 

 13.88 days, while 393 females averaged 13.49 days. This 

 variation is of course very small, but interesting, and might 

 lead to considerable speculation. 



In considering- the development of the boll weevil it is al- 

 ways necessary to divide those stages which have developed 

 from fallen squares from those which have developed in 

 squares hanging on the plant. This has been necessary be- 

 cause the percentage of mortality is always different and also 

 because the factors which cause the mortality are different. 



