28 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 
which they can reach near the surface of the ground. A large 
number of eggs are laid close to one another, and no doubt two or 
more females deposit their eggs so close together that they form 
one gall. The eggs are laid in August, and the galls begin to 
grow in September, but from the fall of the leaf until the spring 
they do not increase in size. In May they are full grown, but the 
gall flies do not emerge until the following April. The galls vary 
in size from about } of an inch to 3 inches diameter, and will 
be found full of small oval cells, each containing an insect. The 
flies which issue from these galls are known as Aphilotrix radicis, 
and only females appear in this generation. They are much 
larger than their parents, measuring nearly a quarter of an inch 
in Jength. They leave the galls in April or May, and deposit 
their eggs in buds which form the young shoots, causing swellings 
to appear at the base of the shoot, from which the flies emerge in 
August. This species, therefore, requires two years to complete 
the cycle of its transformation. 
The Artichoke Gall, so called from its resemblance in form 
to the globe artichoke. This is formed by an insect called 
Andricus pilosus. Both sexes appear in June, and the female 
lays a single egg ina bud, which causes it to grow into a scaly 
bract. On cutting open one of these galls the interior will 
be found of a woody texture, and partly embedded in the top 
is a small, hard, brown, oval striated gall, which contains the 
grub, This gall eventually falls to the ground, when the trans- 
formation of the insect is completed. In the woody portion of 
the outer gall may often be found cells containing grubs of 
some other species, which has laid eggs after its formation was 
begun. The perfect insects, Aphilotrix fecundatrix, bred from the 
internal galls, are about one-eighth of an inch in length, and always 
females. They appear in April, and attack the buds containing 
the male flowers, within which their eggs are laid. The galls 
which result are oval-pointed, about one-tenth of an inch in 
length, covered with stiff hairs, and of a green colour. The perfect 
insects, which are of both sexes, escape from the galls in June, 
and attack the leaf-buds as already mentioned. 
The Spangle Gall insect (Spathegaster baccarum) deposits its 
eggs on the underside of the leaf at the beginning of June, and the 
galls begin to form in July, and are full grown in September, when 
they are about three-tenths of an inch in diameter. They are flat 
and circular, with the centre raised in a flat cone. They are of a 
