THE GRAPE PHYLLOXERA IN CALIFORNIA. 89 



The experiments began June 27 and terminated September 7. Three 

 hundred and ninety-seven migrants produced a total of 143 eggs 

 from which no sexual forms developed. Thus the proportion of 

 deposited eggs to migrants in 1913 was 1 to 3.2, while in 1914 it was 

 1 to 2.75, and in 1911, 1 to 4.3. In 1914 four migrants each deposited 

 four eggs, and three eggs were deposited in nine instances, but most 

 of the eggs were laid singly. In no case could it be definitely said 

 that eggs of more than one sex occurred in individual groups. About 

 three times as many female eggs as male were deposited, and about 

 one-fourth of the eggs were intermediate in size (probably males). 

 The winged sexuparse died on the average two and one-half days 

 after they were admitted to the cages, or about four days after they 

 had transformed from the nymphal instar. 



In 1915 experiments were continued, migrants being secured from 

 June 26 to October 27. Part of these were used in stender and petri 

 dishes, part in small circular rubber cells ( T 3 <- inch high, 1^ inches 

 in diameter) mounted on microscope slides with cover glasses for 

 lids, and a few on a living vine (Riparia). In the dishes small 

 pieces of vine, bark, or leaves were placed, leaves of the Champini 

 being used mostly on account of the fact that the migrants prefer 

 to deposit eggs on a tomentous leaf. The effect of variations in 

 temperature and humidity was noted. 



A total of 1,961 migrants deposited in all 472 eggs, and 52 sexuals 

 matured. Thus the proportion of eggs to migrants was approxi- 

 mately 1 to 4.15. In the stender and petri dishes and on the living 

 vine combined, 938 migrants deposited 167 eggs, a proportion of 5.6 

 to 1, of which 16 sexuals matured. In the rubber cells mounted on 

 microscope slides, 1,023 migrants deposited 305 eggs, a proportion 

 of 3.3 to 1, and 36 sexed forms matured. The rubber cells therefore 

 gave a greater proportion of eggs per migrant. Part of these cells 

 were kept in a cellar and part inside a slide box in a room of the 

 laboratory. The egg deposition was not appreciably different in 

 these two situations, but the sexes under the almost constant tem- 

 peratures of the cellar matured better than under the fluctuating 

 temperatures of the room. Part of the dishes also were kept in the 

 cellar and part exposed to light in the room. Those in the latter 

 situation averaged more eggs per migrant, but the proportion of 

 sexes which subsequently matured was similar to that of the migrants 

 and dissimilar to that of the eggs. 



It appeared at first that exposure to light induced the migrants to 

 deposit a greater proportion of eggs and later appeared to have 

 prevented a large proportion from maturing. Judging from the 

 fact that the amount of light to which these eggs were subjected 

 during their development was not greater than occurs under natural 

 conditions, however, it would appear that this supposition is incor- 



