26 First Report on Economic Zoology. 
may be bought. Numbers of these fruit trees are introduced and the 
scales may be also brought over with the plants. If the scale is- 
seen the plants should be fumigated or destroyed. 
The Brown Currant Scale ( Lecanium ribis ) has also been found 
on plum trees, especially in gardens when the trees are grown 
against walls. 
Sprayers. 
For bush-fruit the best sprayers are the “Knapsack sprayers/' 
the “Eclair,” the “ Notus,” the “Anti-pest,” and others. 
Ordinary syringes are of no use in washing plants. The 
insecticide must be sent out in the finest possible spray. 
Paraffin emulsion should be used first in April for currant scale 
and repeatedly every two weeks for at least two months ; for 
mussel scale in May, and likewise onwards. 
It is advisable to try caustic alkali wash alone for the first year. 
This need not be put on by a “ mistifier,” as the object is to saturate 
the tree, not to spread a fine even layer of the wash over it as when 
Paris green or emulsions are used. 
The Apple Bark Louse or Mussel Scale. 
( Mytilaspis pomorum, Linn.) 
Several correspondents of the Board of Agriculture have reported 
damages to apple trees by the mussel scale, namely, from liomsey, 
Tarporley, Hayling Island, and other places previously mentioned. 
One correspondent thought the scale connected with thrips and 
canker fungus. 
The best way to destroy this scale is to use the caustic alkali 
wash in winter, and spray in the spring and early summer with 
paraffin emulsion. 
A full account of this pest is given on page 75. 
Eggs on Apple Trees and a further Remedy 
for Mussel Scale. 
(i) Apple shoots sent to the Board of Agriculture from South 
Norwood were covered with the eggs of (1) the Red Spider ( Bryobia- 
'pruni ), (2) the Apple Sucker ( Psylla mail). The former are red 
globular eggs, the latter are elongated oval and white. Two only of 
the Psylla eggs could be detected. The majority of the Bryobia eggs 
