200 Bulletin 157. 



the leaf where they can be easily gotten at with a spray. Several 

 of the grubs usually work on the same leaf, continuing to eat 

 small irregular holes, through or nearly through the leaf until it 

 is pretty well riddled like the one shown in figure 18, when they 

 seek new pastures. Where the grubs are numerous, all of the 

 leaves on a branch may be riddled, as in figure 19. page 205. 



As the grubs increase in size they have to shed their skin from time to 

 time, at least two or three times. In shedding their skin or moulting, the 

 old skin splits down the back, about a third of their length, and the grub 

 with its new suit quietly crawls out, leaving its old suit stretched out on 

 the leaf resembling somewhat one of the grubs which might have gotten 

 too warm and had simply unbuttoned its coat down the back a little way to 

 cool oflF. One of these cast-off suits is shown magnified, at b in figure 14. 



The grubs continue to feed upon the upper surface of the 

 grape leaves for three or four weeks before they attain their full 

 growth. The full grown grub is represented in figure 13. 

 They are then scarcely a third of an inch long and their general 

 color is considerably lighter than wdien young, so that the dark 

 markings are more easily distinguished. Owing to their small 

 size, the grubs of this grape pest are not often noticed by the 

 grape-growers ; in fact we fear that but few^ who suffer from this 

 insect are familiar wdth it in the grub state. However, the w^ork 

 of the grubs is easily seen, and grape-growers should learn to 

 know them, for one of the most effective methods of controlling 

 the insect depends upon this knowledge. In New^ York the 

 grubs are to be found at w^ork during the first three weeks in 

 June. 



The pupa stage. — When the grubs have fed sufficiently they 

 drop from the grape leaves, and after working their way for 

 from one-half an inch to two inches in the ground, they twist 

 and roll themselves about until a small smooth cavity is formed 

 around them. In this cavity they change in a few days to the 

 inert stage in their existence — the pupa. In New York many of 

 the grubs were full grown by June 15th, 1898, and a few days 

 later most of them had left the vines and disappeared in the 

 ground. By June 27th most of them were in the pupa state in 

 their little earthen cells. 



One of these pupae is showm, much enlarged, at a in figure 14, 



