ANIMAL PESTS AND DISEASES. 427 



stems. The dozer is filled with water and coated 

 with a film of kerosene. It is used in the warm part 

 of the day because then the hoppers are decidedly 

 most active. 



When it is drawn forward through the infested 

 field, the hoppers spring to get out of its way and 

 most of them may land in the water and be de- 

 stroyed by contact with the kerosene. If enough 

 turkeys and guineas are kept hoppers will be much 

 reduced in numbers. 



Ants. Webworms, army worms, fall army 

 worms, cutworms and blister beetles all occasionally 

 injure alfalfa more or less. Mound-building ants are 

 troublesome in western fields. The ants are readily 

 destroyed by use of bisulphide of carbon. Taking 

 note that the ants are canny and carefully guard 

 their homes, Prof. Headlee thus comments : 



On the approach of a storm a large force is employed and the 

 gateways are closed in haste, but when it has passed they are re- 

 opened and the ants return to their work. 



The ant colonies are too few to decrease the yield seriously, 

 although occasionally they will destroy the alfalfa on from one 

 to two per cent of the total area of a badly infested field. Their 

 claim to rank as alfalfa pests lies principally in the increased 

 difficulty of harvesting the crop when they are present. 



Extended experiments have shown that the ants can most 

 easily and efficiently be controlled by fumigating the nest with 

 carbon bisulphide as follows: Set fumigation only when gateways 

 are open; invert a galvanized iron vessel, such a common wash- 

 tub, over one or more of the openings, covering as much of the 

 mound as possible; firmly pack soil over such holes as the* tub 

 will not reach; introduce under the tub and near the holes a 

 shallow dish containing from one to three ounces (depending on 

 the size of the nest) of carbon bisulphide; set the tub down and 

 quickly pack soil about the rim, making it as nearly air-tight as 

 possible; allow to stand for five hours. The forming vapor, being 



