46 
BULLETIN 879, U. S. DEPARTMENT OF AGRICULTURE. 
all statements regarding one insect will probably apply equally well 
to the other. The work with Diabrotica duodecimpunctata was done 
in the same manner as that with 12. vittata, and the results were 
similar, as is shown in Table XIX. 
Table XIX. — Transmission of cucumber mosaic by Diabrotica duodecimpunctata in 
experiments at Madison, Wis. X 
Number 
of 
beetles 
per 
cage. 
Source of beetles. 
Method of infection of 
beetles. 
Number 
of plants 
per cage. 
Results. 
Date beetles 
were caged. 
Number 
of mosaic 
plants. 
Date of last 
observation. 
Aug. 16,1917 
Do 
35 
35 
35 
25 
25 
25 
25 
25 
Madison, Wis 
do. 
Natural infection 
..do 
4 
3 
5 
5 
5 
5 
5 
5 
3 
2 
1 
3 
3 
1 
2 

Aug. 30,1917 
Do. 
Do 
do. 
...do 
Do. 
Aug. 21,1917 
Do 
.do ... 
....do 
Sept, 20, 1917 
Do. 
do. 
..do 
Do 
do. 
....do 
Do. 
Do 
do 
.do.. . 
Do. 
Do 
do. 
...do 
Do. 
TRANSMISSION BY OTHER CUCUMBER INSECTS. 
It is quite possible that other insects attacking the cucumber may 
also transmit the disease, but they are probably of less importance. 
The tarnished plant bug (Lygus pratensis L.), being a sucking insect, 
very probably carries the disease to some extent, but the few tests 
made with this insect have given negative results. Thrips (Tlirips 
tabaci Lind.), the red spider (Tetranychus telarius L.), and the white 
fly (Aleyrodes vaporariorum Westw.) have shown no indications of 
being carriers of the disease, although greenhouse observations have 
included a large number of cases where the insects were constantly 
feeding on adjacent healthy and mosaic plants. This is in agree- 
ment with the work of Allard (5), who found that neither the white* 
fly nor the red spider acted as carriers of tobacco mosaic in the 
greenhouse. 
TRANSMISSION BY BEES. 
The cucumber and other cucurbits which blossom heavily through- 
out the season are constantly frequented by great numbers of bees. 
These insects might therefore be important agents in disease dis- 
semination, provided they carry the infection. However, the evi- 
dence thus far secured indicates that little, if any, infection is so 
carried. To test this possibility bees were taken directly from the 
blossoms of mosaic plants and then caged with healthy plants fori 
some time. Infection has never been known to occur, although 
trials have been made with 53 plants. As stated on page 33, all 
attempts at artificial inoculation through the blossoms have so far 
failed, and it is likely that if infection occurs at this point it is 
