THE GRAPE PHYLLOXERA IN CALIFORNIA. 



119 



In a fourth experiment 26 eggs were placed in water in a stender 

 dish. Two days later all but four eggs had sunk, but subsequently 

 all eggs hatched and none of the resultant larvae settled on the roots 

 provided for them. 



Table XXXVI indicates the results of experiments bearing on the 

 behavior of newly hatched larvae in water. 



Table XXXVI. — Behavior in loater of newly hatched larvae of the grape 

 phylloxera, Walnut Creek, Calif. 





Number of indi- 





Number of indi- 







viduals 





viduals after 







that — 





submersion. 





Date 





Length 

 of sub- 









placed 











Remarks. 



in water. 





Re- 



mersion. 











Sank. 



mained 

 on 



surface. 





Alive. 



Dead. 





May 12 



5 



3 



Days. 

 1 



8 







In stender dish without cover. 



12 



4 



2 



2 



6 







In small vial — uncorked. 



27 



2 







2 



2 







Do. 



15 



4 



2 



3 



2 



4 



In small vial— uncorked; sunk aphids dead. 



19 



5 



1 



3 



1 



5 



Do. 



June 1 



4 



2 



4 



1 



5 



In small vial — uncorked; sunk aphids alive. 



May 24 



1 



1 



5 



1 



1 



Do. 



June 1 







4 



6 



3 



1 



In small vial — uncorked. 



16 



5 



1 



7 



5 



1 



In small vial — uncorked; sunk aphids alive, but 

 none subsequently fastened on root. 



16 



5 



2 



7 







7 



In small vial — corked. 



1 







4 



9 



1 



3 



Do. 



July 15 



6 



2 



4 



8 







In small vial— corked; one aphid subsequently 

 matured Aug. 12 on severed root. 



15 



6 



2 



4 



•8 







In small vial— uncorked;- one aphid subse- 

 quently matured Aug. 11 on severed root. 



Note. — In all except the first experiment, distilled water was used; in the first experiment, tap 

 water. 



Prior to June 16 the phylloxera? were not followed up after 

 their submersion to see whether they would fasten to the pieces of 

 roots provided for them because the experiments were made only 

 to ascertain how many of the larvae would be alive after submersion. 

 It may be noted that in some cases the larvse which sank were found 

 to be alive when removed from the water and in others those that 

 floated were living when removed. The phylloxeras survived as 

 many as nine days on the surface of the water, and as many as 

 seven days when submerged, and at the bottom of the vial. The 

 experiments, however, did not continue beyond nine days, and there 

 is no reason to believe that the insects could not live in the water 

 many days longer than that period. The fact that they did survive 

 as long as a week was sufficient evidence of the importance of their 

 resistance to water. The two experiments of July 15-19 demon- 

 strated that after four days in water the young larvae could settle 

 on pieces of roots and later mature. In the seven-day experiment, 

 none settled on the roots. In all except one of the vials distilled 

 water at about 64° F. was used. The behavior of the young phyl- 

 loxeras in water was characteristic. Those on the surface were active. 



