List of the Insect Fauna of the County. 149
These galls are multilocular; the larva; pupate in the gall,
and the imagos emerge therefrom in May. Cecidomyia
Salicis, Schrank.
Salix Caprea, L. Leaf. Small, hard, pustular galls,
occurring on the side veins of the leaf, often in considerable
numbers ; they are about the size of a small hemp-seed when
single and mature; are conical in shape, projecting both on
the upper and under side of the leaf; are hard and woody,
and pale greenish in colour. The gall is single-celled, but
we very commonly find large numbers confluent together;
sometimes the gall takes the form of a much-thickened, hard
midrib, extending the whole length of the leaf, and occupying
half its extent; often yellowish or red in colour. Such galls
are frequently left attached to the twigs during winter, and
then show the numerous small round holes from which the
larvae have emerged; they leave the galls in autumn and
pupate in the earth, the flies appearing in May. Hormomyia
capreae, Winnertz.
Salix Caprea, L. Leaf. Bound, hairy, green, rarely
reddish, thin-walled, succulent galls, occurring on the under
side of the leaf, attached only at
one point, and showing as a dis-
coloured spot above. In rare cases
the gall is produced on the upper
side of the leaf, and then is smooth
and rosy. Each gall is tenanted
by a single larva, which eats a
small circular hole through, and
quits it in September; it pupates
in a cocoon in the earth, and the
sawfly appears in May or June.
Nematus viminalis, Linne. (Fig. 50.)
We probably have other "pea" Fig. 50. Nematus viminalis
gall-makers in the county, but
these closely-allied Nemati and their distinctive galls are but
indifferently known in this country. The sallow "rosette"
galls are also probably distinct from those above referred to,
as occurring on S. alba, S. fragilis, &c.