Rejuedial Measures and Insecticides . xv 



consideration in comparison with the damage that may be effected 

 by a single imported pest. What, for instance, must have been 

 the pecuniary loss to the colony from the ravages of the ' green 

 bug' — a loss that, in all probability, might have been prevented. 

 And compare this loss with the value of all the delicate plants that 

 have ever been imported into Ceylon ! But, for such tender plants, 

 it is possible to employ other treatment than is recommended for 

 hardy shrubs and trees. 



For wholesale fumigation of plants and fruit there is nothing 

 to equal hydrocyanic acid gas, generated by mixing cyanide of 

 potassium, water, and sulphuric acid in certain proportions. This 

 treatment is cheap and effectual. The gas is of the most deadly 

 nature, and will penetrate every crack and crevice, and do its work 

 thoroughly. The application is quite simple. All that is required 

 is a close-fitting chamber, provided with a flue for the escape of 

 the gas after the operation. The more air-tight the chamber, the 

 more complete will be the work. It should be fitted with racks to 

 receive removable trays, upon which fruit may be spread. The 

 objects to be fumigated are placed into position ; the chemicals 

 are mixed in a leaden or earthenware pan and placed on the floor, 

 the door shut, and the room kept closed for from half to three- 

 quarters of an hour. The flue is then opened, and, after a sufficient 

 time (about half an hour) has been allowed for ventilation, the door 

 is unlocked, and the plants, &c , removed. It is not advisable to 

 take the subjected plants directly into the open air if the sun is 

 shining. They should be kept for a few hours under shade, which 

 will greatly lessen any danger of damage. 



Mr, C. P. Lounsbury, official Entomologist at Cape Town, has 

 kindly supplied me with full particulars of the work of the 

 Fumigatorium at that place. From his letters and reports I have 

 extracted the following directions and suggestions : — 



For each 300 cubic feet of space enclosed (and in proportion 

 for greater and smaller spaces) i ounce of 98 per cent, potassium 

 cyanide, i ounce of sulphuric acid, and 2 ounces of water will be 

 required to generate gas of sufficient strength to kill the insects. 

 Double this strength, or the same amount of materials to 150 cubic 

 feet enclosed, may be used upon woody plants without danger of 

 seriously injuring them. The greater strength should be employed 

 whenever practicable, as it will ensure the death of the eggs as 

 well as the active insects. 



Imported plants are usually in a more or less dormant condi- 



