SCALE INSECTS 49 
making an infusion of quassia chips. But excellent 
insecticides can be purchased already prepared, which are 
guaranteed to be safe and effective, and being of uniform 
strength, they may be used with confidence if the instruc- 
tions given with the preparations are observed strictly. 
Avoid using paraffin and emulsions of paraffin, for it 
is dangerous, not only to the plants sponged with it, but 
to all the plants in the house, for it affects the atmosphere. 
SCALE INSECTS 
These appear much less in collections now than for- 
merly, because the old large specimens are replaced by 
young and vigorous plants. Thirty or forty years ago, 
it was a usual thing to spend several days every year 
scraping the brown scales from tall plants of Aérides 
odoratum, Vanda tricolor, and other specimen Orchids, 
and what was called “cleaning” was going on all the 
year round. Now there is much less need of such work, 
although scale will appear in its various species on one 
section of plants or another. In the periodical inspections, 
all plants attacked by it should have the insects removed 
by a piece of stick blunted at the edge and point, sponging 
the leaves afterwards with some diluted insecticide. Syring- 
ing with an insecticide, or dipping the plants in the liquid, 
should be avoided, for the quantity applied is likely to 
saturate the material in which the plants are potted and to 
run into the centres of the young growths and cause injury. 
By means of a sponge, it may be applied lightly or heavily, 
but the operator has command in each case over what he 
is doing. 
D 
