No. 4.] INJUEIOUS INSECTS. 161 



many of the small terminal twigs as possible, and all of these 

 twigs should be burned. 



The gas treatment, or fumigation, as it is called in Cali- 

 fornia, consists in covering the tree or plant with a tent or 

 cover of some kind, to prevent the escape of the gas, keep- 

 ing it covered from fifteen minutes to an hour. This tent 

 should be made of duck, and receive two coats of linseed oil 

 and lamp-black, the former to render it air-tight and the lat- 

 ter to exclude the actinic rays of light, as otherwise it would 

 injure the foliage. It would be better, however, to perform 

 this work by night, or on cloudy days. After putting the 

 tent over the tree, raise the windward side from the ground 

 and place an earthenware bowl, containing one fluid ounce 

 of sulphuric acid (66°) and three fluid ounces of water, on 

 the ground inside of the tent, and with a long-handled dip- 

 per or ladle pour one ounce of refined potassium cyanide 

 (98 per cent) into the bowl, and immediately close the tent. 

 This amount is sufficient for one hundred and fifty cubic feet 

 of space within the tent. The chemicals react and form 

 hydrocyanic acid gas, commonly called " Prussic acid," 

 which is one of the deadliest poisons known, and must there- 

 fore be used with the utmost care. 



It is a well-known fact that our nurserymen do not raise 

 all the stock they have a call for, and to fill many orders 

 they are frequently obliged to purchase from outside parties, 

 and in this way they are liable to handle and sell infested 

 stock unintentionally, even when their own nurseries contain 

 no scales. Messrs. Southworth Bros., nurserymen in Salem, 

 realizing this difiiculty, have constructed a fumigating box 

 twelve feet long and three feet high and wide, in which they 

 propose to treat small lots of stock ; but larger lots will be 

 treated in their storage cellar, which is twenty-nine feet long, 

 seventeen feet wide and eight feet deep. These gentlemen 

 propose to carry out this plan, in spite of all obstacles. 



Pure kerosene, applied either with a sprayer or brush, is 

 the latest insecticide that has been recommended for the San 

 Jose scale. Prof. F. M. Webster first called attention to it 

 at the meeting of the Association of Economic Entomologists, 

 held in Bufialo, N. Y., in August, 1896 ; and quite recently 



