THE GRAPE PHYLLOXERA IN CALIFORNIA. 101 



feeding insects. This form generally occurred on resistant vines, 

 but also on viniferae along with the sexuparous migrants. The indi- 

 viduals exhibited much diversity in development, ranging from those 

 with large wing pads to others bearing no vestige of wing pads, but 

 having more fully developed eyes than the typical adult radicicoles. 

 In nearly every case their eggs were parthenogenetic, the resultant 

 larvae becoming root feeders. This form has been styled " inter- 

 mediate," in that it is intermediate in structure between the, radi- 

 cicole and the winged form. Observations indicate that it occurs 

 rather infrequently in California. It has been discussed under the 

 heading " Nymphicals or intermediate forms" (p. 82). All the 

 fully winged individuals observed in California which deposited eggs 

 were sexuparous. 



To sum up, it is not believed that in California there is diffusion 

 through the winged form. It is perhaps worth while to record 

 some observations upon the behavior of the insects of this form in 

 the vineyard. During July and August, 1914, these occurred in a 

 Zinfandel vineyard badly infested with phylloxera. Previously 

 roots of many of the vines on lighter soil had been dug up, and it 

 had been found that a large production of migrants was developing, 

 especially on vines having the external appearance of not being badly 

 phylloxerated. The condition of the roots on this type indicated 

 that phylloxeration had not been in progress more than two years 

 and the tuberosities had not reached a stage of advanced decay ; but 

 phylloxerae were abundant, and it was evident that another year 

 would find the vines much less thrifty. Sticky paper, tacked to 

 boards, was placed in the vineyards, both on the surface of the 

 ground in a horizontal position and in a vertical position. The hori- 

 zontal papers were placed beside infested vines at distances varying 

 from 6 inches to 5 feet from the trunks. The vertical boards were 

 placed throughout the infested part and outside of the vineyard 

 and extended from the soil surface to a height of 7-J feet. More 

 winged migrants were obtained on horizontal boards than on the 

 vertical boards in proportion to a given area of paper. The majority 

 of migrants caught on the horizontal boards were found at the 

 edges, indicating that they reached the papers by walking rather 

 than by flight. In some cases where individuals were found in the 

 middle of the sticky papers it appeared that these might have 

 fallen down from canes of the vine above, but in many instances the 

 phylloxeras obviously had reached the papers by flight or had been 

 blown thither by the wind. Those on the vertical papers had either 

 been borne by the wind or had flown voluntarily. On the vertical 

 boards facing away from the prevailing wind no migrants were 

 caught. Vertical boards with sticky paper were placed in the vine- 

 yard on the following dates: June 20; July 7, 10, 13, 21, 24, 31; 



