40 Transactions British Mycological Society. 
in that case the controlling factor is probably climatic. On the 
other hand, in a small plantation of mulberry trees at Pera- 
deniya, it is always possible to find Sphaerostilbe aurantticola 
in the rainy season, but only on a few trees, though a large 
number of trees may be attacked by the same scale insect; in 
that case, some other than climatic factors must be involved. 
The problem which has yet to be solved by those who wish 
to control insects by means of fungi is how to create an epidemic 
at a time when such an epidemic would not occur naturally. 
The evidence indicates that it is not possible to accomplish that 
by the mere introduction of the fungus or by spraying spores 
from natural or artificial cultures. The solution of the problem 
probably depends in each case upon a study of the bionomics 
of the insect, and it is satisfactory to note that the United States 
Department of Agriculture has appointed a Myco-entomologist 
specially to investigate these diseases of insects. 
I should like to make my position on this point clear. I do 
not for one moment wish to deny that it may be possible ulti- 
mately to discover what factors govern the incidence of these 
diseases of insects, and that, in consequence of such discovery, 
it may be possible to utilise them to control insect pests. But 
I do hold that, in the present state of our knowledge, after nearly 
thirty years of investigation and experiment, there are no facts 
which would warrant the recommendation of any such means 
of control. 
Though the majority of the scale insect fungi are tropical, 
there is some work to be done on them in the British Isles. We 
require more material of Cordyceps pistillariaeformis, which has 
occurred on a Lecanium on elm. Sphaerostilbe flammea is appa- 
rently rare in Britain, but it should be sought for in the winter 
on Chionaspis salicis on willow and ash. The insect is especially 
abundant on ash, coppiced ash in hedge rows being generally 
badly infested. Fusarium epicoccum, not yet recorded as 
British, should be found in the same situation, and it might 
be possible to determine its perithecial stage. A Verticilliwm 
has recently been collected on the same host in Yorkshire; it 
forms a delicate white mould over the colony of scale insects. 
With the exception of the Cordyceps, all the scale insect fungi 
found in Britain have occurred on Chionaspis. In the tropics, 
Aspidiotus and Lepidosaphes are the favourite hosts of the 
Neciria group, and it should be possible to find species on the 
common scale insects of fruit trees in Britain, if search is made 
for them in the winter. 
