THE GRAPE PHYLLOXERA IN CALIFORNIA. 79 
vines (mostly resistants and American nonresistants) during Sep- 
tember and October, and some were reared in the cellar during 
August. 
In 1913 the first nymph was observed, July 9, on the root of an 
xVmerican vine, and at about the same time others appeared on 
young resistant hybrids in pots. On the severed pieces of vinifera 
roots kept in jars in the cellar nymphs occurred as early as July 12, 
and on July 17 the first migrants appeared. This was the first year 
in which experiments were conducted with living vines in cages, 
and on these the earliest nymphs and migrants were reared on 
July 20 and 28, respectively. In the experimental vineyard (Zin- 
fandel) migrants were first collected about August 1, but some 
nymphs were found on July 25 in a vineyard at Napa, Calif. In 
general, migrants continued to develop until November, but after 
the middle of October their production was scanty, and in the vine- 
yard very few were found later than September. 
In 1914 nymphs were first observed on June 16, both in the ex- 
perimental vineyard at Walnut Creek and on roots kept in the 
cellar. On June 18 a migrant was reared from a nymph collected 
in the vineyard two days previously. On the roots of the vines 
growing in cages nymphs were reared June 23. Throughout July 
and August nymphs and migrants were abundant in the Zinfandel 
vineyard. In September the numbers fell off rapidly and none were 
found in October. In infested vines in pots migrants were secured 
in considerable numbers throughout August and September, but 
were much more scarce in October. 
In 1915, in the material reared under cellar conditions, the first 
nymph was observed on June 14. The day following, a nymph oc- 
curred on the root of a young vine planted in a section cage. In the 
cages containing living vines, the first nymph was reared June 23, 
and in the experimental Zinfandel vineyard, nymphs were collected 
June 22 and evidently occurred as early as June 15. In the vineyard 
the production of migrants continued until the end of September, 
and was abundant v from July 15 to the end of August. In the ma- 
terial in the cellar jars, abundant migrants were secured throughout 
the months of July, August, and September, and the production con- 
tinued until November 8. 
In summing up, it may be said that in California the period in 
which migrants are developed in vineyards extends from the middle 
of June until the end of October ; that these forms appear in great- 
est abundance from the middle of July to the middle of September 
(the hottest time of the year) ; and that the production is very 
limited in June and October. In small vines in pots, especially if 
consistent irrigation is practiced, the October production of migrants 
