THE MOSAIC DISEASE OF CUCURBITS. 57 
THE RELATION OF STRIPED CUCUMBER BEETLES TO OVERWINTERING. 
The work of Rand (23) on the Diabrotica species as possible carriers 
of the bacterial wilt organism (Bacillus traclieipMlus Smith) has 
already shown that these insects are an important factor in the over- 
wintering of one of the diseases of cucurbits and strengthened the 
hypothesis that they might bear the same relation to mosaic over- 
wintering. The striped cucumber beetle (Diabrotica vittata) and the 
12-spotted beetle (D. duodecimpunctata) both overwinter in the adult 
stage, emerging from hibernation in the spring, and thus offer a more 
definite possibility of overwintering the disease than the aphis, so 
that the later experiments have all been with the Diabrotica species. 
Artificial hibernation experiments. — The work with beetles was done 
by the writer in cooperation with Mr. Neale F. Howard, of the 
Bureau of Entomology, United States Department of Agriculture. 
Mr. Howard took entire charge of the collection and caging of the 
' beetles and of all work pertaining to the actual hibernation and life 
history of the insects, and the writer conducted the tests relative 
to disease transmission by these insects. 
In the fall of 1916 some 8,000 beetles, chiefly Diabrotica vittata, 
were collected from fields about Madison, Wis., where mosaic was 
prevalent. The beetles were placed in hibernation cages of various 
sizes and types (PL IX, B) and fed on mosaic cucumber vines and 
fruits as long as such material was available. Most of the cages 
were kept outdoors in various places during the winter, a few being 
in more sheltered locations than others. The base of each cage 
contained from 1 to 3 feet of soil and trash, to furnish favorable 
conditions for hibernation. The number of insects varied with the 
size of the cage, but at least 200 were placed in each cage. During 
the winter some of the smaller cages were brought into the green- 
house at intervals and observed for the possible appearance of the 
beetles. Only three emerged during the winter, however, and no 
infection resulted when they were placed on healthy cucumber 
plants. Aside from these few insects, none appeared from any of 
the cages either in the early spring or in June and July, so that 
no data on beetle overwintering of the disease was obtained from 
these tests. 
During the fall of 1917 these tests were repeated at Madison, Wis., 
on a larger scale, about 35,000 insects, both Diabrotica vittata and 
Diabrotica duodecimpunctata, being used. The beetles were collected 
during September and October and placed in various outdoor loca- 
tions, most of the cages being near points where beetles had appeared 
early that spring. Fifteen cages were used in these experiments, 
each having from 500 to 5,000 insects, most of them containing 
from 2,000 to 3,000. The cages were usually made with the base 
extending deeply into the soil but open at the bottom; the soil 
