164 Aphides and Sauwflies [CH. 
underground as well as on the shoots. In this case in 
addition to spraying the trees it is necessary to inject 
carbon disulphide into the soil in order to kill those on 
the roots. If the root forms are not killed the tree 
soon becomes infected by them. Painting the affected 
parts with methylated spirit or paraffin or spraying 
with paraffin emulsion has proved useful in keeping 
down woolly aphis. 
Carelessness among certain nurserymen in allowing 
their young stock to become infected is responsible for 
a large amount of damage done by this pest. 
Various winter washes have proved effective in 
reducing fruit aphides by preventing the eggs from 
hatching. 
Sawrflies. 
Sawflies are not true flies as they possess two pairs 
of wings. They belong to the same family as bees and 
wasps. 
Corn Sawfly (Cephus pygmaeus). 
This pest rarely does much damage in this country. 
It attacks wheat and oats. 
The eggs are laid in the stems of young plants and 
the larvae which hatch out feed on the soft substance 
inside and eat their way through the knots. About 
harvest time the maggots are fully grown and they 
make their way to the bottom of the stem where they 
eat a ring almost round it. The attacked plants may 
be picked out as the shoots die and the dead ears are 
easily seen among the ripening corn. 
Unlike the larvae of most sawflies the maggots seem 
to be legless: as their legs are too small’ to be-seen. 
