138 DESTRUCTIVE INSECTS OF VICTORIA: 



or kill the worms ; and from this pan I lead a pipe directly into the sack . 

 Applying heat to the pan by a lamp or by fuel introduced into the ' 

 furnace, the smoke generated from the tobacco or other substance in 

 the pan is thrown into the sack and soon fills it, coming into contact 

 with all the leaves, and either killing or instantly dislodging every worm 

 and all other insects that may be in the tree. 



This method of destroying insects on trees could not have been very 

 widely adopted. Dr. A. S. Packard, who for several years held the 

 office of entomologist to the Massachusetts State Board of Agriculture, 

 writes me that he is not aware that this method has been practised in 

 any part of the Atlantic States. I can find no reference to it, nor to 

 any similar method having been used in any of the States east of the 

 Rocky Mountains from the date of the Hatch patent up to the present 

 time. 



For several years past many attempts at destroying scale-insects with 

 gases and fumes have been made in southern California. For this 

 purpose the infested tree was inclosed in an air-tight tent, the lower 

 part of which was either fastened around the trunk of the tree or allowed 

 to fall upon the ground ; in the latter case a small quantity of earth 

 was thrown upon the lower part of it, to prevent the escape of the gas 

 or smoke. The tent was then filled with the smoke or gas experimented 

 with. 



Among the first to make experiments of this kind were Messrs. J. 

 W. Wolfskill and Alexander Craw, of Los Angeles ; Mr. John Wheeler, 

 of San Francisco ; Hon. J. DeBarth Shorb, Col. J. R. Dobbins, and 

 Mr. B. M. Lelong, of San Gabriel. The substance most commonly 

 experimented with was the liquid bisulphide of carbon (CS 2 ), but this 

 did not prove entirely satisfactory, owing to the time required for it to 

 evaporate and become diffused in the tent. 



Probably no person has spent more time and money in trying to 

 discover some effectual method for destroying the scale-insects with gas 

 than has Mr. J. W. Wolfskill, of Los Angeles. In a paper read at a 

 meeting of fruit-growers, held in this city on the 7th of October, 1887, 

 Mr. Alexander Craw gave an account of the experiments made by 

 Mr. Wolfskill and himself, from which we extract the following : 



" Previous to the year 1884 we had only the Black Scale (Lecanium 

 olece) to contend with in the Wolfskill orange groves, and these scales were 

 easily kept in check by an application of whale-oil soap in the form of 

 a spray ; one application every two years was sufficient. In the fall of 

 the year 1 884 we found a few trees on the south side of the large grove 

 infested with the Cottony Cushion-scale (Icerya purchasi) ; they became 

 infested from an adjoining grove. We prepared for war, and soon had 

 our spraying apparatus at work upon them. As we were in for 

 extermination, we made a strong solution of the whale-oil soap so 

 strong it almost defoliated the trees and upon examination it looked 

 as if we had gotten rid of the Icerya. A short time afterward, however, 

 we found that the trees were again infested, and we sprayed again, 

 using as much as 50 gallons of the solution to each tree ; but even with 



