THE GRAPE PHYLLOXERA IN CALIFORNIA. 77 



inch of soil, which was a silty loam mixed with heavier clay loam. 

 In some half-darkened cages, containing potted vines, the nymphs 

 were observed to ascend to the level of the soil surface to transform. 

 On the other hand, occasional nymphs have been found to transform 

 on the roots as much as several feet underground, and many of the 

 resultant migrants failed to reach the surface of the soil. 



HABITS OF WINGED MIGRANTS. 



Occasionally it was noticed in the jars that migrants would thrust 

 their beaks into the roots and appear to feed. While engaged thus 

 they lower the head so as to allow the beak to penetrate the tissues 

 of the root. This organ appears to issue from the mesosternum, 

 because of the curvature of the sheath. The femora are kept hori- 

 zontal, and the antennae are usually in motion. While the insect is 

 walking the antennae are in motion. The migrants, so far as has 

 been noted, never feed after they issue from the soil. At all times 

 they exhibit strong positive phototropism. When placed in a room 

 they seek to crawl toward windows, and their activity is greatly 

 increased when placed in the direct sunlight. If placed in a petri 

 dish in the sunlight, they travel very fast and often take to flight, 

 and are capable of keeping up a walking gait for hours. If the 

 surface upon which they are standing becomes heated, they quickly 

 die. If a vine leaf or other shade-giving object is placed in the dish, 

 the phylloxera? will finally settle on the shady side of the object. 

 In the vineyard most of the winged phylloxeras were observed to 

 issue from the soil by creeping up the stumps of the vine. On arriv- 

 ing at the surface many of them passed to the soil and crawled 

 around aimlessly. Others crawled up the vine, and when they 

 reached a point of vantage, such as the end of a cane, they spread 

 and vibrated their wings, as though inviting the wind to bear them 

 off. Finally they launched themselves into the air and if they struck 

 a wind current were borne off. Often after spreading their wings 

 once or twice they turned about and crawled down the stalk, and 

 frequently when they launched themselves into the air no current of 

 wind caught them, and they half fell and half flew to the ground 

 in an oblique direction, but at other times they flew off strongly 

 without the aid of the wind. The migrants are capable of traveling 

 by flight and with the wind, as is evidenced by the experiments con- 

 ducted with sticky papers. (See Diffusion of phylloxera, p. 100.) 

 They have been taken on such papers at least 80 feet from the near- 

 est infested vine, and undoubtedly they may travel much farther. 



In order to ascertain whether the migrants returned to the soil by 

 crawling down the stem of the vine, 26 migrants were placed on the 

 upper foliage of a small American vine (9 inches in height), on 



