GRAPE ROOT WORM. 231 



larva drops to the ground and makes its way to the roots of the 

 vine through cracks in the soil and by burrowing. Tliese larvae are 

 very tenacious of life and can exist for over a week without food, 

 though prior to finding grape rootlets they may feed upon humus in 

 the soil, and they have been known to travel for several hours at the 

 rate of six feet an hour and to burrow through nearly a foot and a 

 half of soil in four days. However, probably many of them perish 

 before finding the roots of their food-plant. The young larvae feed 

 first upon the finer roots and root-fibers, and later, as they become 

 large, furrow and notch the larger roots. They work within two or 

 three feet of the crown of the vine, and at a variable depth in the 

 soil. During the latter summer and until quite late in the fall the 

 larvae feed extensively, doing much harm and completing about 

 three-fourth of their growth. When cold weather arrives, that is by 

 latter October and early November, they go down deeper into the 

 soil, usually slightly below the roots of the vines, and there con- 

 struct an earthen cell in which they spend the winter. 



Grape-root worms sometimes fall prey to preaaclcus grouna 

 beetles and their larvae, and are eaten to a very liriiited extent by 

 white grubs. The eggs of this species are attacked and destroyed 

 by mites, lady-beetle larvae, lace-winged fly larvae and ants. They are 

 also parasited by two minute species of hymenopterous egg parasites 

 and a dipterous egg parasite. Natural enemies, however, do not 

 seem to be a very potent factor in controlling this pest, and when 

 favorable conditions occur they increase to such an extent that 

 artificial means of control are essential. 



In the artificial control of the grape-root worm the insect is most 

 vulnerable in the pupa and beetle stages. The egg clusters are so 

 effectually concealed and protected in their position under the bark 

 of the grape canes that it is practically impossible to reach them with 

 a killing wash, especially as the vines are in full leaf at the time 

 the eggs are laid. Attempts to kill the larvae in the soil have like- 

 wise proved a failure, either because of total ineffectiveness, pro- 

 hibitive cost or injury to the vines. 



We have seen, however, that in the spring, as the time for pupa- 

 tion approaches, the larvae approach the surface of the soil ani form 

 their pupal cells at a depth of only two to four inches, and that this 

 pupating normally begins about the second week in June, reaching a 

 maximum about the middle of June, and gradually decreasing 

 toward the end of the month. The vineyardist can readily discover 

 the pupas about this time by removing a few inches of soil from 

 about the bases of the vines. When pupation is found to have 

 commenced, the soil beneath the trellis should be removed to a 

 depth of three or four inches with a horse hoe, and the soil immedi- 

 ately surrounding the base of the vine then thoroughly cultivated with 

 the hand hoe. The pupal cells are thus broken up, and the delicate 

 and helpless pupas, being unable to reconstruct them, perish form 



