Insects - Pests of Ornamental Trees, Shrubs and Flowers - page 260

Ditula angustiorana (Haworth) ( 655-656 )
A locally common and polyphagous pest of trees, shrubs
and herbaceous plants, including ornamentals such as
beech ( Fagus sylvatica ), common box ( Buxus
sempervirens ), juniper ( Juniperus ), larch ( Larix ), bay
laurel ( Laurus nobilis ), pine ( Pinus ), flowering cherry
( Prunus ), Rhododendron and yew ( Taxus baccata ).
Widely distributed in Europe; also present in parts of
North Africa and North America.

Larva: up to 10 mm long; yellowish green; head light
brown; prothoracic plate brown to black; thoracic legs
brown. Pupa: 7-8 mm long; reddish yellow or dark
yellow.

LIFE HISTORY
Adults occur in July and August, eggs being deposited
on the bark of the shoots and small branches of host
plants. Eggs hatch in the following spring. Larvae feed
from May to June, each in a shelter formed from two
leaves spun together. When fully fed, individuals pupate
in the larval habitation or in a folded leaf. There is just
one generation annually.

DESCRIPTION
Adult female: 14-18 mm wingspan; fore wings pale
ochreous brown, marked distinctly with dark purplish
brown and black; hind wings dark brown. Egg: pale
yellow, flat and almost circular; laid in a scale-like
batch. Larva: up to 18 mm long; slender, pale yellowish
green to brownish green or greyish green, but darker
above, with light green pinacula; head greenish yellow
or yellowish brown, marked with blackish brown;
prothoracic plate yellowish green, light brown or dark
brown; anal comb greenish or brownish, with four teeth;
thoracic legs green, tipped with blackish brown;
spiracles small, the hindmost twice the diameter of the
others. Pupa: 8 mm long; light brown; cremaster
elongate, with eight tightly hooked setae.

DAMAGE
Larvae cause minor damage to the leaves but
infestations on cultivated plants are unimportant.

Croesia forsskaleana (Linnaeus) ( 654 )
syn. C. forskaliana (Haworth)
Larvae of this widely distributed species feed from
September to May or June on field maple ( Acer
campestre ) and sycamore ( A. pseudoplatanus ); after
hibernation individuals attack the unfurling leaves and
flowers and, later, inhabit a longitudinally rolled leaf.
Although infestations are often common in parks and
gardens, damage caused to cultivated plants is
unimportant. Larvae (up to 10 mm long) are yellow,
with small, pale pinacula, a yellowish-green head and
anal plate, and a greenish prothoracic plate. Adults
(12-15 mm wingspan) are mainly yellow, the fore
wings reticulated with brownish yellow, partly bordered
with black, and more or less suffused centrally with
dark grey. They occur in July and August.

LIFE HISTORY
Adults occur in June and July, the males often flying in
sunshine. Eggs are laid on the leaves in moderately
large batches, and hatch in August. Young larvae feed
on the foliage but in the autumn, whilst still small, they
spin silken cocoons on the buds or spurs. They then
hibernate. The larvae reappear early in the following
spring. They then attack the buds and young leaves,
each spinning tissue together with silk to form a shelter.
The larvae are very active if disturbed, wriggling
backwards and dropping to the ground. Pupation occurs
in May or June in a cocoon spun in a folded leaf, in
webbed foliage or amongst dead leaves on the ground.

654

DAMAGE
Attacked leaves are either grazed on one surface or
bitten right through; attacked young growth is also
distorted but attacks on ornamentals are rarely
sufficiently numerous to cause economic injury.

654 Adult of Croesia forsskaleana .