586 BULLETIN 347 
dissemination. Ruggles states that in some places in eastern Pennsylvania, 
86 to 93.8 per cent of all infections were in wounds produced by the seven- 
teen-year cicada. The bast-miner larve, which are present in great numbers 
on smooth-bark trees, have often been said to be responsible in this way. 
Ruggles states that fifty per cent of the infections in smooth-bark trees 
originated in the exit holes of these insects. He also suggests their respon- 
sibility for the numerous crotch infections, since they oviposit near 
crotches. Anderson and Babcock, on the other hand, were unable to 
produce infection by making inoculations in exit holes of these insects, 
The pustules of the fungus are often eaten by some insects, the most 
common of these being Leptostylus maculata; but experiments have 
proved that the spores, after being eaten, are digested and do not serve 
to spread the disease. Craighead (1912) reports five different species of 
insects which he found eating the pustules, but believes that they con- 
tribute to the control of the disease rather than to its spread. The United 
States Bureau of Entomology has made much of these discoveries and 
has suggested that these beneficial insects may be a large factor in the 
final control of the disease (Pennsylvania Chestnut Tree Blight Commis- 
sion, 1914). Ruggles, however, shows that the insect mentioned above, 
Leptostylus maculata, carries enormous numbers of spores on its body, 
and suggests that it is more injurious as a disseminator of spores than 
beneficial as a destroyer. 
Metcalf and Collins (1911) state that in many parts of the country 
the two-lined chestnut-borer (Agrilus bilineatus) is directly associated 
with ninety per cent of all cases of the disease. It was to the so-called 
bast-miner, however, that they referred, rather than to the borer mentioned 
(Ruggles, 1913). 
Davis (Penn. Chestnut Tree Blight Com., 1913:48) attributes to ants 
seventy-five to ninety per cent of the cases of infection in the locality 
where he was working. The grounds for the statement are the fact that 
, no summer nor winter spores could be found and yet the disease continued 
to spread, and also the fact that ants were found carrying mycelial threads 
of the fungus. The anomalous condition of trees in an affected area not 
producing any spores, and Davis’ proof that the mycelium carried by the 
ants was really that of Endothia parasitica and that it was deposited in 
‘wounds favorable for infection, require further explanation. 
Rain 
‘Rain dissolves the mucilaginous matrix of the spore fiaens: and the 
pycnospores are washed down the trunks where they lodge in wounds 
and produce cankers. They may also be splashed to other trees that 
are in close proximity to diseased ones. This accounts for the fact that 
