GALLS CAUSED BY MITES 
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at maturity. They are usually present in great numbers, 
and project almost equally from both surfaces of the leaf. 
The aperture is in the centre of a depression in the con¬ 
vexity on the upper surface. I found these galls in great 
abundance on Berry Head, Brixham, in June, 1909; about 
the same time they were taken by the late Edward Connold 
at Hastings. They are not common, and had not, to my 
knowledge, been observed hitherto in Britain. 
Yew buds are not infrequently attacked by Eriophycs 
psilaspis. Affected ones become swollen (Plate XXL, 
Fig. 9), attaining 8 mm. in diameter. They do not unfold, 
are often tinted with yellow, and minutely granulated. The 
mites are very numerous, and congregate between the scales. 
This gall was first noticed in Britain in the spring of 1875, 
when it occurred in great numbers in Yew hedges near 
London. It is frequent on trees and bushes that have been 
clipped. 
Eriophyes viburni causes small red pustules (about 5 mm. in 
diameter) to appear on the upper surface of the leaves of the 
Mealy Guelder Rose (Plate XXL, Fig. 5). The pustules are 
usually coalescent, often occurring in such numbers as almost 
completely to cover the leaf, which, however, is never greatly 
deformed. These galls are covered with tufts of short, stiff 
hairs. The opening is on the lower surface, and is surrounded 
by a felt of hairs; the interior is lined with hairs, amidst 
which the mites may be found in hundreds. Various aspects 
of the gall under low magnification are shown in Plate XXL, 
Figs. 6 and 7. The Mealy Guelder Rose is frequent in the 
large wood on the hill to the north of Weston-super-Mare. 
A careful examination in June, 1910, revealed only two bushes 
afflicted with the mites. These were growing side by side, 
and the majority of their leaves, excepting the young 
ones, bore the characteristic galls in enormous numbers 
(Plate XXL, Fig. 5); closely adjacent bushes were quite 
free. The limitation of the mites to two bushes only, in a 
large wood containing hundreds of these bushes, is of great 
interest. The non-infection of the majority cannot be 
