THE GRAPE PHYLLOXERA IN CALIFORNIA. 43 



On the Muscadine the phylloxera upon hatching from the eggs 

 refused to settle or feed. The nonresistant varieties were infested 

 throughout summer and autumn, and on their roots the phylloxerse 

 entered into hibernation from September 20 to the beginning of No- 

 vember; in the case of the Champion, they hibernated as late as 

 December 1. On the Catawba and Champion, the most heavily in- 

 fested, the aphids began hibernation earlier; on the less infested 

 Delaware, Isabella, and Lenoir, somewhat later. 



Aphids became active about the middle of February, and all 

 hibernants were adult by April 13. This spring activity was some- 

 what in advance of that occurring in vineyards, but was similar to 

 that which occurred on the caged vinifera vines. On all nonresist- 

 ant varieties it was observed that the hibernants massed on tuberosi- 

 ties, nodosities, and the normal surface of the roots; and in cracks in 

 a manner similar to that observed to occur on vinifera vines. 



On the resistant hybrids repeated inoculations during summer 

 and autumn failed to produce more than an extremely light in- 

 festation. The phylloxeras settled to hibernate during October, and 

 at the end of that month all were hibernants. They were situated 

 on side rootlets and on the normal surface of the root, but on the 

 Rupestris St. George hibernants occurred also on nodosities which 

 they had caused to form shortly after they settled. 



Hibernation on American vines in pots, 1912-1915. — A large series 

 of 2-year-old vines (from cuttings) planted in 6-inch pots, originally 

 used in resistance experiments and comprising resistant vines, we^e 

 examined during the years 1912 and 1913 for hibernant observations. 

 It was found that hibernation took place during the last half of 

 October and first half of November and that the spring awakening 

 proceeded from about March 10 to April 15. These vines were 

 planted in light sandy soil. The hibernants settled chiefly on nodosi- 

 ties and to a smaller extent on the surface of the larger rootlets. In 

 the spring there was a great variation in the growth of the vines. In 

 the majority of instances the phylloxerse on the early leafing vines 

 molted sooner than those on the more backward plants. No tempera- 

 ture records were kept with this series, but it is probable that the 

 records taken 2 feet below the soil surface (Table XII) approxi- 

 mated that which occurred in the pots in the winter of 1913-14. 



A further series (1914) of rooted vines in 9-inch pots, comprising 

 Agawam, Isabella, Lenoir, Delaware, Catawba, and Champion, 

 showed that with the exception of the Delaware, which was lightly 

 infested, hibernation proceeded from about October 1 to November 

 1, nearly all the insects being hibernants on the latter date. On the 

 Delaware none of the phylloxeras were hibernants on October 30, 

 and the roots were on that date still running strongly in sap, while 

 the sap flow in the other varieties was weaker. The temperature in 



