1909] REIFF — FLACHERIE 103 
the two groups of trees had been badly infested and injured by Gypsy Moth cater- 
pillars the previous season, as was evidence by the unhealthiness of the leaves during 
the summer of 1909, and the caterpillars had become predisposed to the disease on 
account of the resulting decrease in the value of their food. As a second very im- 
portant factor may be mentioned the extremely dry weather, which by its desiccating 
effect on the leaves served to render the food for the caterpillars still worse. On this 
account, from the beginning there was a decreased vitality in the tissues and digestion 
was disturbed. In short, the caterpillars were already very susceptible to the disease 
at the time I introduced it among them. Conditions were therefore most suitable for 
the spread of flacherie. Apparently in the places that have been injured by Gypsy 
Moth caterpillars in previous years, there is also a predisposition on the part of cater- 
pillars of the following year toward flacherie, and the organisms of the disease from 
the introduced dead and sick caterpillars will act readily upon the more healthy ones. 
Infection will take place even in cases where a locality is first badly infested by the 
caterpillars, because one can always find a large number of weakly specimens which 
lend themselves more readily to treatment. ‘Then, as the disease progresses, it ac- 
quires such virulence that the previously healthy specimens become susceptible. If, 
however, unusual climatic conditions prevail the disease will find the environment 
already suitable for its dissemination. ‘This ought to be particularly true, if the 
organisms causing the disease should be fungi. In the production of a purely bacte- 
rial disease the climatic conditions would hardly play such a highly important réle. 
There are some other peculiar habits of the larvee which may be important factors 
in the spread of the disease under conditions like those of the third experiment. 
Since the caterpillar is very active just before beginning to feed, and since it likes, when 
half or full-grown, to crawl up and down the tree trunk, it is forced to pass over the 
ring surrounding the trunk and infection results. Serving also to hasten their 
destruction is their peculiar desire to suck the juices of other caterpillars which have 
died of flacherie. They are also very fond of sucking the ring placed on the tree 
and so imbibe directly the diseased material. In cases of extraordinarily dry weather 
one may renew the ring after about two days. The probability of infection between 
caterpillars themselves is also always very:great. ‘The disease is transmitted particu- 
larly during resting periods, for it very commonly happens that the caterpillars become 
gregarious at such times. Then the disease continues to spread when a healthy cater- 
pillar feeds on that part of a leaf which has been previously tasted by a diseased one. 
The excrement of the diseased caterpillars is very moist on account of their digestive 
disturbances, and this infected matter commonly adheres to the leaves and twigs, 
where it readily comes in contact with healthy caterpillars, not to mention the fact that 
