ENDOTHIA CANKER OF CHESTNUT 585 
Insects 
Insects are found in great numbers both in and on chestnut bark, and 
the possibility that they may crawl over sticky spore horns and carry 
spores away to deposit them in wounds, and thus start new cankers, 
has occurred to the majority of writers who have mentioned dissemination. 
It is reasonable to believe that many infections do occur in this way, 
but the mere statement of the probability without experimental data is 
not convincing; and unfortunately such data are meager in the literature. 
In order to prove that an insect — or anything else, for that matter — 
is a direct agent of dissemination, three points must be demonstrated: 
(1) that the insect is in the habit of visiting cankers and actually carrying 
away spores on its body; (2) that it deposits these spores ‘n wounds 
favorable for germination; (3) that infections do result from wounds 
inoculated in this way. To induce insects to crawl over damp spore 
horns or active perithecia and then demonstrate the presence of spores 
on their bodies, is no proof that they are in nature responsible for the 
spread of the disease. Ruggles (Penn. Chestnut Tree Blight Com., 1914) 
has shown the fallacy of this argument. After allowing ants and about 
twenty other species of insects to run over spore horns and active perithecia, 
he was able to isolate spores of Endothia from all of them. Yet he 
proved to his own satisfaction that ants are not responsible for infection. 
The following is from the summary of his work in Bulletin 9 of the 
Pennsylvania Chestnut Tree Blight Commission: “ Two rooms were set off 
in an insectary. The inner of these two rooms being thoroughly sterilized 
was called the sterile room, the outer room was called the blighted room. 
In the latter as much blight material as could be obtained of the kind 
required was kept and placed on the ant table, where three colonies of 
ants made their homes. From the table in this room the ants were allowed 
to run through a glass tube to sterile seedlings in the sterile room. 
The result of the experiment was that with the exception of a few dtied 
leaves on each tree which were chewed or worked on by the ants, the 
trees in the sterile room are as healthy as when first placed on the table 
to be run over by the ants. The indication, therefore, is that ants are 
not responsible for blight infection.” 
Studhalter (1914) also reports the presence of spores on the bodies of 
twenty-four out of seventy-five insects after they had run over cankers 
or had been taken directly from diseased trees in the field. 
Indirectly, insects may be connected with the spread of the disease 
by making wounds in the bark where spores may gain entrance after 
having been carried by some other agent. Anderson and Babcock (1913) 
and Ruggles (Penn. Chestnut Tree Blight Com., 1914) are of the opinion 
that this is the most serious way in which insects are related to blight 
