THE CANADIAN ENTOMOLOGIST. 293 



The reason for considerably more damage being done by the San 

 Jose Scale than by the Oyster-shell Bark-louse is on account of the San 

 Jose Scale producing many broods in one season, and also bringing forth its 

 young alive, whereas the Oyster-Shell Bark-louse is one-brooded and 

 winters over in the egg stage. 



The treatment to be adopted for nearly all the scales is practically 

 the same in all cases. On deciduous trees, where the scales remain 

 during the winter upon trunks and branches, and where the trees become 

 dormant, the scales are best treated during the winter. At that time there 

 is no foliage to interfere, and much stronger washes can be used than 

 would be possible during the summer, or when the tree is active. It is 

 extremely difficult to penetrate insect tissues with ordinary liquids, and it 

 has been found impossible in practice to obtain good results in the 

 destruction of scale insects, except by means of caustics. The common 

 soaps are all caustic, and, when applied in strong solutions, the scale is 

 shrivelled, lifted, and partially corroded, so that the oily mixture works 

 its way beneath into absolute contact with the insect. Or it is raised at 

 the edges and washed off by the rains, carrying with it either eggs or 

 young, as the case may be. In fact, where the eggs hibernate, winter 

 applications act only by exposing .them, so that they are easily washed 

 away by rains and scattered. 



In the case of plants which do not lose their foliage at any period, 

 or in conservatories, or where winter treatment for any reason is not 

 feasible, we must attack the insects when the larvae are crawling about, 

 and before they are fixed. At that time, whilst not protected by a scale, 

 they may be easily killed, alniost any of the contact insecticides being 

 effective. 



Remedies. — Owing to the large number of applicants who were de- 

 sirous of obtaining information on the best methods of combating the 

 Oyster-shell Bark-louse, it was decided to carry on a number of 

 experiments here, to test the efficiency of the various insecticides com- 

 monly used against scale insects. 



Of all the spray mixtures tried, the well-known lime, salt and sulphur 

 wash gave the besc results. 



The lime, sulphur and caustic soda, and the lime, sulphur and sal 

 soda v.ere also tried, but without quite such good results. The lime, 

 sulphur and caustic soda proved to be a little superior to the lime, sulphur 

 and sal soda, owing to its apparent power of better penetration. 



