1916-17.] The Family Chermesidse. 375 
were frequently so numerous as to whiten the larch needles. To repair 
the damage, the dwarf shoots and dormaht buds began to grow. These, 
together with the elongating terminal shoots, provided new and succulent 
food for the succeeding generations of progredientes. Thus the struggles 
of the host to free itself only resulted in its more complete subjugation. 
4. Control. 
The high parthenogenetic developments of the species of the genera 
Chermes and Cnaphalodes on both spruce and larch make it impossible 
that any considerable benefit would result from attempting to eliminate 
either host from any particular plantation. As the species of the Cher- 
mesidse quickly increase on any decline in the health of their hosts, great 
care should be taken that the planting area is clearly suitable to the conifer 
which it is desired to plant. The author is convinced that there is no 
practical method of controlling the pests after a plantation has been formed. 
Specimen trees may be sprayed as suggested by Burdon(12). 
During his observations two facts impressed the author, namely : — 
(a) The species of Chermesidse are frequently widely present in forest 
nurseries. 
( b ) These pests often do serious damage to their hosts immediately 
after a plantation has been formed. 
These facts suggested that it would be exceedingly advantageous if the 
conifers used in the formation of a plantation were free from Chermesidse. 
The author considered that the most practical and thorough method to 
ensure this was the fumigation of the nursery stock immediately before 
dispatch to the planting area. The fumigation of certain classes of nursery 
stock is compulsory in some countries and is practised in many others, but 
not to any great extent in this country. 
The methods employed in carrying out the fumigation experiments have 
been described under “ Technique,” I, 4. They were as simple as possible, 
and will have to be elaborated to ensure complete success. The plants were 
much more seriously infested than would be normally met with, hence this 
method of control was rigorously tested. 
The details and results of the experiments have been embodied in the 
following table : — 
[Table 
