SEASONAL HISTORY. 
41 
Table XVIII. — Complete life cycle of 19 grape root-worms at North East, Pa., reared 
from eggs laid during 1908; adults emerged in 1909. 
Num- 
ber o f 
indi- 
viduals. 
Dai 
Hatch- 
ing of 
eggs, 
19()8. 
e of 
Emer- 
gence of 
beetles, 
1909. 
Number 
of days 
for the 
we 
cycle. 
1 
July 16 
July 
9 
358 
1 
do 
July 
10 
359 
1 
:..do".\\. 
July 
13 
362 
1 
...do.... 
July 
15 
364 
1 
. . .do .... 
July 
17 
366 . 
4 
July 20 
July 
352 
1 
...do 
July 
8 
353 
4 
...do.... 
July 
10 
355 
2 
...do 
July 
11 
356 
1 
...do 
July 
30 
375 
1 
July 25 
July 
20 
366 
1 
...do... . 
July 
27 
367 
19 
6, 810 
SUMMARY. 
Days. 
Average 358.4 
Maximum 375 
Minimum 352 
SEASONAL VARIATIONS IN THE LIFE HISTORY OF THE GRAPE 
ROOT-WORM. 
In comparing the records for the time of emergence of the beetle 
for the three consecutive years of 1907, 1908, and 1909 a marked 
difference in the date of emergence will be found (fig. 16). This varia- 
tion is partly due to the relative lateness of the spring and partly to 
the climatic conditions prevailing during the entire development of 
the insect in the ground. 
The climatic conditions for the years 1906 to 1909, inclusive, have 
been strikingly varied and, as will be seen, the life of the insect tor 
these years has been affected accordingly. The mean temperature 
for 1906 was 1 degree above normal and the precipitation averaged 
about 1 inch below normal. August! and September being particu- 
larly dry and hot. Frost occurred June 11 and 12 ami snow on 
October 10, 11, and 12. The year 1907 was marked with an abnor- 
mally low temperature, a late spring, and an early fall, with a rather 
high precipitation for the summer months. The month of May was 
the coldest on record during a period of eighteen years. In 1908, on 
the contrary, the mean temperature was above normal and the 
summer was marked by two periods of severe drought, the dry condi- 
tions being especially felt during the end of August. In most respects 
1909 (fig. 17) was nearer the average. 
Although 1906 was a favorable season, during which the larviv 
attained a normal growth, yet owing to the late and cold spring of 
1907 the emergence of the insect was very materially delayed and 
