Reports to the Board of Agriculture. 173 
The Canker Caterpillar of the Oak. 
( Tortrix viridccna.) 
The term “ Canker” or “ Blight” caterpillar is sometimes used by 
foresters and labourers when speaking of the Green Oak Tortrix 
( Tortrix viridccna ■). 
The Green Oak Tortrix occurs in great numbers some years, and 
its ravages are often persistent, lasting, as in Windsor Forest, for 
four years (1890-1894). The moth that gives rise to this so-called 
Canker worm or Oak-leaf Roller is about four-fifths of an inch across 
the expanded wings, but varies in size ; the fore wings are uniformly 
pale apple-green, with the costal edge sulphur coloured, the hind 
wings whitish grey, and all the wings have white fringes. They 
appear on the wing in June and July and fly during the day-time. 
They lay their eggs singly or in groups on the buds and pass the 
winter in this stage. The larvae hatch in April and May, and at 
once commence to feed upon the buds and leafage. When mature 
they are about three-fifths of an inch long, grey or greyish-green in 
colour, yellowisli-green posteriorly, with blackish-brown head, and 
small black spots on the back. They not only devour leaf and 
bud, but also the inflorescence. When full fed they roll a leaf up 
and pupate inside the tube, usually in the early part of June; the 
pupa is two-fifths of an inch long, black in colour. The pupie are 
also found in crevices in the bark. A habit very noticeable in the 
caterpillars is that of lowering themselves from the leaves by threads 
of silk, and by means of these silken cords they regain the foliage. 
Small trees in parks and gardens can be cleared by arsenical 
washing. No remedies can be applied in forests. The great thing 
is to protect natural enemies, namely, rooks, jackdaws and starlings, 
which feed upon the caterpillars ; tits devour the eggs. 
The caterpillars of the Dunbar Moth ( Cosmia trapezina) feed 
upon this grul}. 
Besides oak, hornbeam is also attacked by T. viridccna. 
