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These insects are injurious by piercing the sap vessels 

 with their probosces, sucking the juice of the tree, 

 and causing wounds which ulcerate and finally destroy 

 the branch attacked by corroding through all the sap 

 vessels. The excrescences or knobs attendant upon the 

 attacks of these insects are really caused by the 

 efforts of the tree to repair the injuries. The cottony 

 matter is abundant, and, wafted to other trees, proba- 

 bly conveys to them infection, by bearing with it the 

 eggs or embryo insect. But this is not the exclusive 

 mode of diffusing the disease, for although the females 

 are usually wingless, yet, like many other insects, 

 some are probably produced with wings at the season 

 propitious to colonization. The males are uniformly 

 winged. In the winter these insects retire under- 

 ground, and prey upon the roots of the apple-tree. A 

 tree thus ravaged at all seasons will soon be killed, if 

 prompt and vigorous remedies are not adopted. The 

 affected roots may be bared and left exposed for a few 

 days to the cold, and the earth, before returned, be 

 saturated with ammoniacal liquor from the gas works. 

 In early March the branches should be scraped, and 

 scrubbed with the same ammoniacal liquid, or a strong 

 brine of common salt ; but whatever liquid is em- 

 ployed, the scraping and hard bristles of the brush 

 should penetrate every crack in the bark. This treat- 

 ment, repeated and persevered in so long as the least 

 appearance of the insect is observed, never fails of a 



