374 Proceedings of the Royal Society of Edinburgh. [Sess. 
2. Damage to Spruce. 
(a) Genus Chermes s. str. 
The species of this genus attack strong growing spruce, hence the 
damage is primary. Under normal conditions such damage is unim- 
portant, but, allied with unsuitable soil or atmospheric conditions, the 
work of this genus may play an important part in killing the host. On 
the area under observation the generations of the non-migrating species 
did the much greater damage. 
(6) Genus Cnaplialodes. 
The species of this genus only attack thin shaded branches, hence the 
damage, as regards spruce, is secondary. Shaded spruce, however, are 
quickly killed as the galls terminate the twigs. Thus the damage would 
be important where, in thinning a wood, the shaded spruce were left for 
soil protection. As before, the non-migrating species was found to be the 
more dangerous. 
3. Damage to Larch. 
The damage to larch by the species of the two genera Chermes s. str. 
and Cnaplialodes has undoubtedly been greatly increased by the planting 
of that conifer in localities and under conditions very different from those 
of its natural habitat, with a consequent weakening of the tree. The 
species of both the genera are usually present on the same tree. 
(a) Genus Chermes s. str. 
The species of this genus is principally a bark-feeder as regards larch, 
hence the damage is difficult to estimate. Frequently the bark is whitened 
by the “ wool ” and cast skins of the colonici ; later the bark turns black. 
The feeding of these numerous colonici, at a time when growth should be 
at a maximum, must have a weakening effect on the host. The punctures 
are small, but they are made at a time when girth is increasing, so that 
they will be greatly increased in size and become a possible source of 
infection by wound parasitic fungi. The damage resulting from the 
feeding of the sexuparse is unimportant, as its duration is short. 
( b ) Genus Cnaplialodes. 
The species of this genus is a twig- and leaf-feeder on larch. The 
colonici do damage similar to that by colonici of Chermes s. str. In the 
author’s opinion the principal damage is done by the progredientes. They 
