341 - 
were probably unfavourable to the growth of the Coccus. Thus 
drought and mild winters would appear to provide the exact 
conditions under which it is possible for the Coccus to thrive, whilst 
enfeebled health of the trees (due primarily to drought and in some 
cases accelerated by old age) makes them peculiarly susceptible to 
insect attacks. 
From what we can learn, however, the Coccus appears to cause 
very little real harm by sucking the juices of the trees, though 
doubtless, if an already enfeebled tree is badly infested, a certain 
amount of further injury must take place, for it is not in a 
condition to spare even the small amount of food-substances which 
the insect requires, 
The insect may thus be regarded as doing a small amount of 
harm by extracting sap from the outer bark, but any injury it may 
cause would be infinitesimal when compared with Saw-flies and 
other leaf-eating insects and with various fungoid pests. 
That the Coccus has not assumed an epidemic stage is apparent 
everywhere, for, though scores of trees may be found carrying traces 
of Coccus, it is only a tree here and there that is badly affected, and 
those trees are usually far apart. 
In much that has been written on the subject, it appears to have 
been taken for granted that the Coccus eventually kills the trees on 
which it finds a home, and the same opinion prevails largely amongst 
foresters and other people. But there is very little evidence to 
prove that careful observations have been taken of particular trees, 
to ascertain whether death can be traced directly to the insect, or 
whether some other less conspicuous agency may not have played 
the responsible part and been wholly or partially the cause of death. 
Further, it is difficult to obtain reliable information as to the length 
of time a tree, which is said to have been killed by Coccus, lived 
with a considerable amount of Coccus on the bark, Some people 
assert that a period of seven or eight years is required to kill a tree 
after the disease has obtained a footing ; others maintain that three 
or four years is quite long enough, whilst still others have known 
trees to be thickly covered for a period of from 12 years upwards, 
and be vigorous still, as in the case of the tree mentioned in 
Mr. Brotherston’s article. Trees at Kew have been known to bear 
Coccus for at least 20 years, and no serious effects have been traced 
O it. 
The conclusion we have arrived at is that while the Coccus is 
doing very little harm, certain fungoid pests account for a serious 
amount of injury, which is usually credited to Coccus. On all the 
dead trees pointed out to us as having been killed by Coceus, we 
found destructive parasitic fungi present, which alone would account 
for the death of trees. The same fungi kill or injure other kinds of 
trees on which the Beech Coccus does not oceur. 
wo parasitic species were common. In cases where the trees 
had broken off 15 or 20 feet from the ground, in the region where 
the fructification of the fungus (the wound parasite, Nectria 
ditissima, Tul.) was most prevalent, patches of a dull red colour were 
seen on the bark. They were not conspicuous and might be easily 
overlooked. The patches were due to numerous minute, red, 
granular lumps, which form the fructification of the fungus. The 
21218 B 
