SEASONAL HISTOKY. 



35 



Table XI. — Field observations on the hatching of eggs of the grape root-worm in the 

 valley and on the hill in the vicinity of North East, Pa., 1909. 



In the valley. 



On the hill. 



Date. 



Number 



of 

 clusters 

 counted. 



Percent- 

 age of 

 clusters 

 hatched. 



Date. 



Number 



of 

 clusters 

 counted. 



Percent- 

 age of 

 clusters 

 hatched. 



July 30. . . 

 Aug. 4... 

 Aug. 12.. 

 Aug. 19.. 

 Aug. 26 . . 

 Sept. 2... 



41 



70 

 67 

 90 

 103 

 78 



39 

 42 

 70 

 91 

 97 

 100 



July 30... 

 Aug. 13.. 

 Aug. 19.. 

 Aug. 26 . . 

 Sept. 2. . . 

 Sept. 9. . 

 • Sept. 16.. 



48 

 56 

 76 

 66 

 97 

 98 

 87 



10 

 40 

 60 

 77 

 81 

 92 

 100 



THE LARVA. 

 VITALITY OF THE NEWLY HATCHED LARVA. 



On hatching, the minute larva drops to the ground and makes its 

 way to the roots of the vine through cracks and crevices in the soil 

 and by burrowing. In this struggle to reach the food supply there 

 is probably always a high percentage that perishes, for the number of 

 eggs deposited is much larger than the number of larvae found later 

 in the ground. 



The power of the young larva to exist for a time without food, 

 liowever, is remarkable. In the breeding of the insect a number of 

 newly hatched larvae, confined in a glass tube, were kept alive for 8 

 days without food or moisture. Interesting experiments showing 

 the burrowing and traveling powers of the young grub were carried 

 out by Dr. E. P. Felt in 1902. This gentleman found that one larva 

 had traveled a distance of over 47 feet in 7 hours, or an average of 

 6 feet an hour. In another experiment he found that 14 young 

 larvae out of 40 penetrated through loose earth in a glass tube 17 

 inches long in a period of 4 days. This tube was one-half inch in 

 diameter and bent so that 4 inches were vertical. In our breeding 

 cages young larvae were found to feed upon the humus of the soil 

 before reaching the root fibers; therefore it is not surprising that 

 many larvae do penetrate to the roots, even under unfavorable con- 

 ditions, and that they are found in vineyards in compact clay soil. 



FEEDING AND DEVELOPMENT OF THE LARVA BEFORE WINTERING. 



During the summer and until late fall the larvae feed extensively, 

 and on an average attain three-fourths the full size and frequently 

 full growth before wintering. 



The young larva feeds mainly upon the finer roots and root fibers 

 of the grapevine. Later it attacks the larger roots, devouring the 

 bark in longitudinal furrows, as shown in Plate III. Sometimes the 



