Agriculture Reference
In-Depth Information
Fig. 331
Pear & cherry slugworm,
Caliroa cerasi
(x8).
Fig. 332
Adult hazel sawfly,
Croesus septentrionalis
(x4).
face. There are usually two, sometimes more,
generations each year.
over the head (a posture common to many spe-
cies of sawfly larvae). Fully fed larvae enter the
soil where they spin brown cocoons. In favour-
able districts, where there is a second generation
of adults in August, larvae may be found from
mid-June to early autumn. Second-generation
larvae overwinter in their subterranean cocoons
and pupate in the spring.
DESCRIPTION
Adult
4-6 mm long, black and shiny.
Larva
up
to 10 mm long;
body
pyriform, distinctly swollen
anteriorly
(Fig. 331),
greenish-yellow to orange-
yellow but covered in a shiny olive-black slime;
thoracic legs
inconspicuous;
abdominal prolegs
seven pairs present.
DESCRIPTION
Adult
8-10 mm long;
head, antennae and thorax
black;
abdomen
mainly reddish-brown;
legs
black, the hind basitarsus and apex of hind tibia
greatly expanded
(Fig. 332)
.
Larva
up to 22 mm
long;
body
pale yellowish-green to bluish-green,
and partly suffused with yellow on the first tho-
racic and apical abdominal segments; prominent,
black, rounded patches along either side of the
body;
head
shiny black;
abdominal prolegs
seven
pairs present
(Fig. 333).
Croesus septentrionalis
(L.)
Hazel sawfly
This generally common sawfly attacks a wide
range of deciduous trees and shrubs (including
Alnus, Betula
and
Corylus).
The larvae often
cause extensive damage to young ornamentals
and can rapidly defoliate the branches; they are
also minor pests in cob nut, filbert and hazel
plantations.
BIOLOGY
Adults appear in May and June. Eggs are then
deposited in small slits made in major leaf veins
of host plants. After egg hatch, the larvae feed
gregariously and voraciously. They rest in
groups, with each larva grasping the leaf edge
with the thoracic legs and arching the abdomen
Dolerus haematodes
Schrank
This sawfly is a minor pest of grasses and cereals,
including wheat and barley. The larvae graze
openly on the leaves and typically devour the
tissue from the tip downwards. Affected leaves
often appear severed and frequently attract
