July i, 1925 Overwintering and Dissemination of Cucurbit Mosaic 
5 
not an agency which can be considered important as a means of over¬ 
wintering the mosaic disease. Only one case of apparent seedling 
infection has occurred in trials with approximately 22,000 cucumber 
plants grown from seed from mosaic plants, and none in the less 
extensive trials with muskmelon, squash, and pumpkin. Aside from 
this single instance there have been perhaps five instances of possible 
seedling infection from commercial cucumber seed and perhaps one 
in the case of the muskmelon. In such cases, however, there has 
usually been considerable doubt as to the actual source of infection. 
In any case, the rarity of such infection has been demonstrated and, 
in view of the prevalence of other sources of primary infection, the 
seed of the cultivated curcubits seems a negligible factor. It should 
be noted, however, as will be shown later, that the seed of the wild 
cucumber, Micrampelis lobata , is an important agency in overwinter¬ 
ing the disease. 
THE STRIPED CUCUMBER BEETLE AS A FACTOR IN OVER¬ 
WINTERING MOSAIC 
Studies of the striped cucumber beetle, Diabrotica vittata , in re¬ 
lation to the overwintering of mosaic, which had been in progress 
prior to 1919 ( 8 ), were continued during 1919 and 1920. The 
major portion of this work was in cooperation with J. E. Dudley, 
jr., of the Bureau of Entomology, United States Department of 
Agriculture. The collection and studies of the hibernation and 
life history of the insect were under his direction, and the studies 
of the beetles as possible carriers of the mosaic virus were conducted 
by the writers. 
TRIALS WITH BEETLES FROM HIBERNATION CAGES 
During the fall of 1918, several thousand beetles were collected 
by Dudley and placed in hibernation cages at various points. The 
beetles were fed on mosaic-diseased leaves and fruits of cucurbits 
as long as such material was available. In the latter part of April, 
1919, 392 beetles which survived the winter were obtained from two 
of these cages and allowed to feed on healthy cucumber plants placed 
under cheesecloth cages in the greenhouse. Fifty small cages were 
placed over individual plants and a single beetle was placed in each 
cage. The remaining beetles were divided into lots of 25 to 80 and 
f daced in larger cages containing several cucumber plants. In a 
ew of the cages, young plants of Micrampelis lobata were included 
with the cucumbers. The beetles thus fed on 120 cucumber plants 
and 21 plants of Micrampelis. The plants were removed from the 
cages after an interval of four to eight days and held for at least 
two weeks for observation, but no signs of mosaic infection developed 
in either species. 
EXPERIMENTS WITH BEETLES COLLECTED IN THE OPEN 
At the time the beetles emerged from hibernation in the spring of 
1920, a considerable number were collected in the open fields and 
fed on healthy cucumber plants under cages in the greenhouse. 
Between April 21 and May 10, 292 beetles were thus obtained and 
allowed to feed in cages containing 85 cucumber and 22 Micrampelis 
plants. No sign of mosaic appeared on any of these plants, although 
they were under observation for four weeks. 
