BACTERIAL WILT OF CUCURBITS. 23 
DISSECTION EXPERIMENTS. 
It is clear from the foregoing that striped beetles in the active state 
are sometimes capable of harboring the wilt organism for consid- 
erable periods of time. With the idea of determining in what part 
of the body the bacteria are carried, the following beetle dissection 
experiments were carried out. 
Six 12-spotted cucumber beetles were fed for three weeks on wilted cucumber 
plants in pots and finally for five days on cut stems and leaves of wilted plants. After 
this last feeding (Aug. 8, 1917) the heads and legs of the beetles were removed sep- 
arately with sterile instruments. Then the anal region was cut off with a hot scalpel, 
and the intestinal contents were carefully squeezed out with sterile instruments on 
a sterile Petri dish, using care that none of the contents should come in contact 
with the exterior of the insect body. Young potted cucumber plants were then 
inoculated separately with heads and mouth parts, legs, intestinal contents, and repro- 
ductive systems. In each case the body parts named were pricked into the young 
leaves without moistening the surfaces. Five days later one leaf inoculated with 
intestinal contents had started to wilt. After two days more, wilt had started in one 
leaf inoculated with beetle legs and in two additional leaves inoculated with intestinal 
contents. This infection from beetle legs is not to be wondered at, as the beetles were 
allowed to feed on cut stems and leaves of wilted plants for several days prior to dis- 
section. These plants had been kept throughout the test in a large 6-foot square 
beetle-free cage (PI. II, fig. 1) and were entirely free from insect gnawings. A hundred 
or more uninoculated cucumber seedlings of the same age and variety held as controls 
in the same cage remained free from the disease. 
On August 16, 1917, the preceding experiment was duplicated, using six striped 
and twelve 12-spotted cucumber beetles. Five days later one of the plants inoculated 
with intestines and one inoculated with legs of the 12-spotted species were found with 
wilt. In this case none of the plants inoculated with head parts became infected. 
During the summer of 1918 four more sets of dissection tests were carried out. On 
June 15, after a 7-day's feeding on wilted plants, forty striped and three 12-spotted 
cucumber beetles were dissected as in preceding experiments, and separate cucum- 
ber seedlings were inoculated with heads and with intestinal contents. Ten of the 
forty striped beetles were feeding on wilted leaves when taken. The other thirty were 
not feeding when taken for dissection. In these cases the body parts were crushed in a 
drop of tap water and pricked into the cucumber leaves. In 11 days two plants arfd 
next day three more plants showed wilt starting from leaves inoculated with intestinal 
contents. Of these five wilted plants only one was infected from one of the ten beetles 
feeding on wilt when taken; the other four wilted plants were from four of the thirty 
beetles not feeding when taken. Cultures made from one of these plants gave Bacillus 
tracheiphilus, and all five showed typical wilt symptoms. No infections resulted from 
the three 12-spotted beetles. 
This experiment was repeated on June 28, using 45 striped beetles. In eight days 
two plants were wilting from beetle-intestine inoculations and the following day two 
more from intestines and one from head and mouth parts. Cultures were made from 
the first two plants showing wilt, and Bacillus tracheiphilus was isolated and proved 
to be virulent by successful inoculations. 
Sterile instruments were used and great care was taken in all these tests not to allow 
the intestines to come in contact with external body parts. However, in order com- 
pletely to eliminate all possible source of external contamination, the beetles in the 
following two tests were immersed for five minutes previous to dissection in a 1 to 1,000 
solution of mercuric chlorid in 25 per cent alcohol. The alcohol was added to facili- 
