THE GRAPE PHYLLOXERA IlsT CALIFORNIA. 45 



In 1913, between June 26 and November 14, a series of observations 

 on fecundity under adverse food conditions was made. Among a 

 large number of aphids, on two occasions only were as many as six 

 eggs deposited in one day by a single individual. In the cellar, 431 

 eggs were deposited in a total of 331 days (1.3 eggs per diem per 

 aphid) , and in an electric incubator, wherein a slightly higher 

 temperature was maintained, 787 eggs were laid in a total of 463 days 

 (1.7 eggs per diem per aphid). These averages were considerably 

 less than corresponding ones found to result in the 1911 series, yet the 

 insects raised in the incubator were subjected to higher temperatures 

 than were those in 1911, raised in the cellar. 



Egg deposition on living vines. — During the years 1913, 1914, and 

 1915, series of generations were raised on living vines in cages. These 

 vines were all vinif erge, and comprised the following varieties : 

 Muscat, Zinfandel, Mission, Burger, Thompson's Seedless, and Gren- 

 ache. The principal object in this work was to check up on the 

 previous 2-year study of root cuttings under cellar conditions. The 

 initial inoculations in 1913 were made with eggs laid by adults of the 

 overwintered generation on Zinfandel vines in the vineyard, and thus 

 no record of the egg production of the overwintered adults was 

 secured in the cages. Of the first generation, records of 10 indi- 

 viduals were taken, but a complete record of only one was made, and 

 this adult, between June 25 and July 14 (20 days) , deposited 121 eggs, 

 the largest number in a single day being 12. The 10 adults deposited 

 482 eggs in 95 days, or an average of 3.1 eggs per diem per adult. 



Most of the individuals died early, and it is assumed that if they 

 had been allowed to lay their full complement of eggs, the period 

 of decline would have reduced this average. These adults were pro- 

 duced, 7 on Burger roots and 3 on Mission roots. It appeared that 

 those on the Mission were the more prolific. On both varieties 

 some were situated on lesions they had caused to form. These aver- 

 aged better in egg production than the others situated on the nor- 

 mal root surface. Records for 14 adults of the second generation 

 were taken. On a very healthy Mission root, living on lesions, 4 

 adults averaged 4.5 eggs per adult per diem. On two less healthy 

 Mission roots of the same cage vine, 6 averaged 2.4 eggs per adult 

 per diem. On a very healthy Burger root 4 averaged 3.9. The 

 longest egg-laying period for any adult of this generation was 26 

 days and the maximum eggs per day 15. In all, 489 eggs were laid 

 in 136 days, 3.6 eggs per adult per diem. 



The egg-laying period of this generation ran from July 8 to 

 August 15, with an average temperature of 68° F. Four adults of 

 the third generation deposited 284 eggs in 88 days, at an average 

 of 3.2 eggs per diem per adult; the longest egg-laying period was 

 28 days and the maximum number of eggs per diem was 8. These 



