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 Aerides 

 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 



