78 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 



August 17, 1914. Around the base of the vine stem were placed 

 sticky papers, and the stem was encircled with glue. The vine was 

 kept indoors and was not exposed to wind currents. Six hours after 

 the phylloxerse were placed on the leaves, eight individuals were 

 caught on the paper. After 24 hours, 17 winged phylloxera were 

 on the paper and 3 dead on the leaves, none having been caught in 

 the circle of glue on the stem. Thus the phylloxeras had either flown 

 or dropped down and none had descended the full length of the stalk. 

 Since none of the individuals on the papers were over 4 inches from 

 the stem it would appear that they dropped rather than flew from 

 the vine. 



On August 22, 1914, 34 winged phylloxeras were placed on the 

 foliage of a riparia vine, 12 inches in height. This vine was potted 

 and sunk in the soil and exposed to field conditions. Around the base 

 an area of sticky paper 30 by 36 inches was laid. After two days an 

 examination of the paper showed on the leeward side eight winged 

 phylloxeras, occurring 16^, 16J, 16, 16, 12, 10, 6, and 1^ inches, respec- 

 tively, from the stem, and one winged phylloxera on the windward 

 side 2 inches from the stem. The remaining 25 were not recovered, 

 and probably flew off or were blown beyond the paper. The location 

 in which this experiment took place was subjected to wind that blew 

 from one direction only. It is obvious that the wind was a factor in 

 the distribution of these phylloxerse. 



In the observations on the flying of the migrants it was found 

 that individuals would fly both in the sunlight and in the shade, 

 that very frequently they refused to launch themselves even in 

 bright sunlight and in all varieties of wind currents, and that they 

 appeared to take no definite direction in launching themselves. As 

 a general rule, the winged forms fly more abundantly in the sun- 

 shine than in the shade, and they are the more active the hotter and 

 drier are the conditions of their environment. 



PRODUCTION AND RELATIVE ABUNDANCE OF MIGRANTS. 



In 1911, in the course of rearing experiments conducted in the 

 laboratory cellar, the first winged forms were secured on August 2. 

 These had been raised on a heavily infested piece of vinifera root 

 and were part of the third generation of that year. In five localities 

 in central California nymphs were collected in vineyards from 

 August 3 to 19 and, judging from observations made in years fol- 

 lowing, it is possible that nymphs had been developed earlier in 

 that season. In the laboratory the production of migrants proceeded 

 until the end of November, but in the latter half of October and in 

 November only a few developed. 



In 1912 no record was made of the earliest appearance of nymphs 

 and migrants, but they were found abundantly on young potted 



