62 
THE GKAPE ROOT-WORM. 
the soil to make its pupal cell, this plan of cultivation has been some- 
what modified. In order to encourage the larva to come still higher 
above the roots of the vine to pupate than it would have done under 
ordinary cultural methods it has become customary to throw up a 
ridge of soil beneath the trellis at the last cultivation of the preced- 
ing summer (see PL V, fig. 2). Observations have shown that it is 
highly desirable that this ridge be formed under the trellis late in the 
summer rather than in the early spring, since in the former case the 
soil becomes of a uniform compactness by the time the larvae are 
ready to migrate nearer to the surface to pupate; whereas, if the 
ridge is formed in the spring a layer of trash and leaves accumulating 
under the trellis during the winter is sandwiched in this ridge, and in 
no case in our examinations have we found pupal cells above this 
layer of trash. In the operation of horse hoeing this spring-formed 
ridge away from the vines it frequently happens that only the layer 
above the trash is thrown away, hence the pupae, which are all 
beneath the trash, are undisturbed. 
Undoubtedly this modification in the plan of early cultivation of 
vineyards is an important aid in the destruction of this pest at a 
time when it is in its most critical stage of development. Instances 
have come directly under our observation where we have seen great 
numbers of the pupae exposed to the air and sunlight or become the 
immediate prey of birds and predaceous insects. The operation is 
probably of greater value in sandy and loose gravelly soils than in 
stiff clay soils, for in the former the earthen cells fall apart quite 
readily with the disturbance of the soil, leaving the pupae exposed; 
whereas in the clay the soil is more likely to turn over in lumps, leav- 
ing many of the cells intact. In addition to this, in soils of a sandy 
or gravelly nature the loose earth around the vines may be removed 
by the horse hoe to a much greater depth and more pupae disturbed 
than in the case of stiff clay soils, where it frequently happens that 
the operation of horse hoeing amounts to little more than a scraping 
of the weeds from the surface of the ground, especially if the season 
be a dry one. In fact, the drying out of the soil is the chief draw- 
back to placing reliance on this operation as a means of controlling 
this pest. 
It not infreque ltly happens that a dry period may occur along the 
Lake Erie Valley during the month of June which renders it difficult to 
make horse hoeing as thorough and as timely as it should be to derive 
the greatest benefit from this operation in the destruction of the 
pupae. In the summer of 1907 when the development of the pupae 
was unusually late the operation of horse hoeing was postponed by 
some vineyardists until the last of June and early July in order to 
perform it at a time when the maximum number of the insects were 
in the pupal stage, and considerable complaint was forthcoming 
