List of the Insect Fauna of the County. 147
considerably lengthened. The gall is single-celled, and when
mature in June falls with the catkin, but the gall-fly does
not emerge therefrom until the succeeding spring. Andricus
quadrilineatus, Hartig. (Fig. 47.)
Fig. 47. Andricus quadrilineatus.
Salix alba, L. Leaf. The bean-shaped galls on the leaf
are very common, and generally well known. They are oval
or bean-shaped, and occur four or five in
a row on each side of the midrib (with
which, however, they have no con-
nection), but sometimes only singly;
the galls are thick and fleshy, projecting
both from the upper and under surface
of the leaf, but more so from the under
side; here they are generally green or
whitish-green and pubescent, above they
are bright red. Only one larva lives in
a gall, eating the fleshy walls to a mere
shell, when it bites a hole through and
falls to the ground, where it pupates in
a thick brown cocoon. The sawfly ap-
pears in May and September, being
double - brooded. Nematus gallicola,
Westwood. (Fig. 48.)
The galls of this species occur com-
monly on Salix fragilis, L.; those on
S. Caprea, which are similar, but not so Nematus gallicola.