32 



oped embryo completely fills the interior of the egg^ its large head 

 being in one end and its body curved ventrally upon itself till nearly 

 double. Considerable motion is manifested if the egg be touched at 

 this period. 



DURATION OF EGG STAGE. 



Concealed as the eggs are beneath several layers of vegetable tissue, 

 it is impossible to examine them to ascertain the exact length of the 

 egg stage without in some degree interfering with the naturalness of 

 the accompanying conditions. The beginning of the stage was easily 

 obtained by confining female weevils with uninfested squares. Care- 

 ful dissections were then made of the squares at a little later than 

 what was found to be the average embryonic period at that season. 

 In this way it is believed the range of error was reduced to a fraction 

 of a day in most cases, and a large number of observations were made 

 to still further reduce the error. 



As shown by Table III, 631 observations have been recorded upon 

 this point, the majority of the observations being made in the fall of 

 1902. Considering the temperatures prevailing at the four periods 

 studied, it appears that the range in development during the average 

 season at Victoria, Tex., has been included, and it seems probable 

 that from these temperatures as a basis the length of the egg stage 

 can be approximately determined for any season and for an}^ locality 

 within the present area of infestation. 



Table III. — Duration of egg stage at certain periods. 



Period of examination. 



Number 

 of obser- 

 vations. 



Mean 

 temper- 

 ature for 

 period. 



Average 

 effective 

 temper- 

 ature, a 



Average 



duration 



of egg 



stage. 



1902. 



September 4 to October 3 



October 7 to November 13 



November 27 to December 15 . . . 



1903. 

 May 27 to June 5 



1904. 

 Experiments in ice box 



Total 



385 



107 



36 



25 



81.0 

 73.0 

 62.0 



72.5 

 70.0 



38.0 

 30.0 

 19.0 



32.5 

 27.0 



Days. 

 2. 5 to 3. 

 4, to 4. 5 

 11.0 



3.5 to 4.0 

 5.1 



631 



5 3.6 to 4.2 



a In considering the influence of temperature upon the weevils it has been found that with the weevil, 

 as has been found to be the case with many animals, 43° F. is about the lowest temperature at which 

 activity is shown. Temperatures below that point would, therefore, have no influence upon activity, 

 while all above that point would. For this reason, it is better to speak of the "effective temper- 

 ature," meaning by that the number of degrees above 43° F. Experiments made upon the influence 

 of temperature upon the activity of weevils indicate that this is an approximately correct figure for 

 this insect. 



b Weighted average. 



The extreme range observed in Table III in the duration of this 

 stage is from 2 to 16 days, while the average period for the whole 

 number of observations is but 3.6 days. It is possible that the embryo 

 can undergo an even greater retardation without losing its vitality. 



