50 
THE GRAPE ROOT-WORM. 
vations with field conditions, and whenever differences have occurred 
corrections in the summary (fig. 23) have been made to approximate 
field conditions. 
SUMMARY OF LIFE-HISTORY STUDIES OF THE GRAPE ROOT-WORM. 
The life history of the beetle (see fig. 12, p. 23) may be briefly sum- 
marized as follows: The grape root- worm produces only one genera- 
tion a year; the larva feeds on the roots of the grapevine, and in this 
stage the insect is found in the ground for the greater part of the year. 
In early June the full-grown larva makes an earthen cell a few inches 
below the surface of the ground, within which it pupates about the 
middle of June ; the pupal stage lasts generally twenty days, and the 
beetle or adult begins to emerge from the ground in late June or early 
July, while a few belated beetles continue to appear in the early part 
of August. On an average the beetle feeds for from 10 to 13 days on 
the grape foliage before ovipositing. The eggs are laid beneath the 
loose bark on the canes of the vines, and hatch on an average in 12 
days; the young larva drops to the ground and soon finds its way to 
the roots of the vine ; generally the larva becomes three-fourths grown 
and sometimes attains its full growth in the fall. Previous to win- 
tering it penetrates deeper into the ground, below the roots, and there 
constructs an earthen cell in which it passes the winter. 
The diagram (fig. 23) shows the relative occurrence and the time of 
transformation of the grape root-worm in its various stages. It has 
been prepared from field observations and rearing records of 1909 and 
is a summary graphically presenting the life-history studies. 
Local variations in the times of development of the different stages 
of the insect, as described in preceding pages, may be brought about 
by various factors, such as differences in the texture of the soil, rela- 
tive abundance of food, and altitude and exposure of vineyards. 
The seasonal variations, as shown by the difference in the time of 
emergence of beetles during 1907, 1908, and 1909, and also by the 
occurrence of larvae that remained two winters in the soil, are the 
direct results of climatic influences. The insect has a strong tendency, 
however, to develop normally, even under adverse conditions. 
NATURAL ENEMIES. 
PREDACEOUS INSECTS. 
Several predaceous insects have been found feeding upon the larvae 
of the grape root-worm. During the process of digging for larvae, 
both in the spring and fall, various species of carabid beetles and their 
larvae have been found in the ground. These insects are entirely pre- 
daceous and probably feed upon the grubs of the grape root-worm 
whenever the latter come within their reach. Dr. E. P. Felt recorded 
