184 



UNIVERSITY OF CALIFORNIA EXPERIMENT STATION. 



Proportion of the Sexes of Overwintering Hoppers. 



Fig. 5. Tip of abdomen of female grape leaf-hopper, 

 showing ovipositor. The black tipped appendages, 

 the cerci, obscure the other parts of the ovipositor 

 shown in Fig. 6 below. Greatly enlarged. 



It will be seen from the average percentage in the above table that 

 there is practically no difference between the numbers of the sexes, 



so that we may con- 

 clude that both sexes 

 are able to withstand 

 the winter conditions 

 equally well. 



Migrations. When 

 plowing is begun in 

 the vineyard in the 

 spring, before the 

 foliage appears on the 

 vine, the food supply 

 consisting of what- 

 ever vegetation may 

 be growing is 

 turned under and 

 most of the hoppers are obliged to look elsewhere for food. Some of the 

 insects remain in the vineyard and subsist upon what little growth may 

 be left by the plow. The larger number, however, must look elsewhere 

 for food, and this is generally found in the immediate vicinity, usually 

 around the borders of the vineyard. We have seen all the vegetation 

 growing along the roadsides of badly infested vineyards completely 

 deprived of the green coloring matter. After the vineyard was plowed 

 the hoppers continued to feed here, largely, until the vines came into 

 leaf, when they migrated back into the vineyards. These are the only 

 distinct movements we have observed with the overwintering hoppers 

 in the spring. 



Time they Attack the Vine. The first observed feeding on the grape 

 foliage at Lodi during 1907 was March 28th, on an old Mission vine- 

 yard that was considerably in advance of the other surrounding vine- 

 yards. A week or two later, however, the foliage in many vineyards 

 was far enough along to attract a good many of the hoppers from their 



