SEASONAL HISTORY. 



25 



VARIATION IN THE TIME OF EMERGENCE. 



The variation found in the time of emergence of beetles in different 

 vineyards and even in different sections of the same vineyard is due 

 to various factors, such as temperature, moisture, porosity and tex- 

 ture of the soil, etc. 



Since larvse are found more abundantly in the looser porous soils 

 than in the heavy, compact clay soils, and since the former soils are 

 warmer, it is but natural that the insect should emerge earlier under 

 these conditions. This fact is confirmed by observations, presented 

 in figure 14, which shows the relative emergence of beetles from three 

 grades of soil. For these experiments a number of larvae were col- 

 lected in the early spring from different localities in the vicinity of 

 North East, Pa. They were confined in large earthen pots (fig. 22) 

 with the same kinds of soil in which they had been collected. Since 

 these larvae were supplied with a sufficient amount of food and the 















n 



1 



1 





; \ :;| ::::::: 



■ 6 



zs^ 



I WW :;i:| i : :A '■. 





::I::^:m: 



i 



m 



Mi : : ;; 



IIM 





1 



1 



■If 



ry-'r^wr'^-'T/-^-:'-:---- 



' -^: -f:^-'^^ ■■■■ 



1 n ;: 





JULY 



z 



i t f- 



- . i It ir 11. -7 .« // it il it ti i'/ -IS 



a >^ it sf J* j/AUQ.^ J y i 



Fig. 14.— Curves showing variations in time of emergence of beetles of the grape root-worm from 

 different kinds of soil. From rearing experiments during 1909 at North East, Pa. (Original.) 



pots were placed in the ground in the open, it is believed that their 

 normal conditions had been changed but slightly. The emergence 

 of beetles from the sandy and gravelly soil was seven days earlier 

 than the emergence from the clay soil. 



In the vicinity of North East, Pa., the authors have observed that 

 the emergence of the beetle in vineyards situated on the hills is one 

 week later than the emergence in vineyards in the valley. This delay 

 is not merely confined to the time of emergence of the beetles, but 

 has been observed in practically ah the different stages of the insect, 

 as can be verified from the various tables of field observations. 



FEEDING BEFORE AND AFTER * EGG DEPOSITION. 



At the time of emergence from the ground the beetle seems to 

 possess a keen appetite. It readily finds its way to the grape foliage, 

 and generally feeds upon the first leaf that it encounters. The leaves 

 of the lower shoots are frequently found badly mutilated as a result 



