44 
THE GRAPE ROOT-WORM. 
Table XIX. — Percentage of 2-year-old larvae of the grape root-worm as recorded in 
vineyards in the vicinity of North East, Pa., in the fall of 1909. 
Vineyard in silt soil in the valley. 
Vineyard on loamy soil in the 
valley. 
Vineyard on gravelly loam on 
the hill. 
Date of 
digging. 
Num- 
ber of 
vines 
exam- 
ined. 
Total 
num- 
ber of 
larvae. 
Per- 
centage 
of old 
larvae. 
Date of 
digging. 
Num- 
ber of 
vines 
exam- 
ined. 
Total 
num- 
ber of 
larvae. 
Per- 
centage 
of old 
larva?. 
Date of 
digging. 
Num- 
ber of 
vines 
exam- 
ined. 
Total 
num- 
ber of 
larvae. 
Per- 
centage 
of old 
larvae. 
Aug. 17 
to 
Oct. 12 
| 32 
328 
3.0 
Aug. 10 
to 
Sept. 20 
} ^ 
449 
0. GG 
Sept. 2 
to 
Oct. 7 
} " 
517 
5.0 
The percentages of twice-wintering larvae in Table XIX represent 
only records of early observations when a number of larvae had not 
yet been hatched. It is of interest to note that the percentage of 
2-year-old larvae was largest in vineyards located on the hill, owing 
to the prevailing shorter season on the hill as compared with the 
season in the valley. The time of transformation of the insects in 
other stages has similarly been affected by the climatic conditions of 
the past three years. 
In Table XX is shown the relative number of maturing insects and 
twice-wintering larvae which were reared from eggs deposited at 
known dates in 1908. 
Table XX. — The relative occurrence of transforming and twice-wintering larvae of the 
grape root-worm reared from eggs laid in cages in 1908, at North East, Pa. 
Date of hatching 
1908. 
Number of 
beetles 
emerging, 
1909. 
Number of 
larva? win- 
tering, 1909 
July 16 
July 20 
July 25 
July 28 
Total 
5 
12 
0 
12 
0 
0 . 
3 
19 
15 
In the rearing experiments other factors beside climatic conditions 
have influenced the results and no direct conclusion should be drawn 
from these observations beyond the point of establishing the fact that 
under unfavorable conditions individual insects of this species do 
remain two years in the ground before maturing. 
REARING AND EXPERIMENTAL METHODS. 
The underground habits of the larvae of the grape root-worm have 
made the rearing of this insect comparatively difficult, and certain 
obstacles have been overcome only by persistent and continued 
experimenting. The rearing work in most cases has been planned 
