HOW TO DESTROY RATS. 



17 



Ferrets. — Tame ferrets, like weasels, are inveterate foes of rats, and 

 can follow the rodents into their retreats. Under favorable circum- 

 stances they are useful aids to the rat catcher, but their value is 

 greatly overestimated. For effective work they require experienced 

 handling and the additional services of a dog or two. Dogs and 

 ferrets must be thoroughly accustomed to each other, and the former 

 must be quiet and steady instead of noisy and excitable. The ferret 

 is used only to bolt the rats, which are killed by the dogs. If un- 

 muzzled ferrets are sent into rat retreats, they are apt to make a kill 

 and then lie up after sucking the blood of their victim. Sometimes 

 they remain for hours in the burrows or escape by other exits and 

 are lost. There is danger that these lost ferrets may adapt them- 

 selves to wild conditions and become a pest by preying upon poultry 

 and birds. 



Fumigation. 



Rats may be destroyed in their burrows in the fields and along 

 river banks, levees, and dikes by carbon bisulphid. A wad of 

 cotton or other absorbent material is saturated with the liquid and 

 then pushed into the burrow, the opening being packed with earth to 

 prevent the escape of the gas. All animals in the burrow are asphyx- 

 iated. Fumigation in buildings is not so effective, because it is dif- 

 ficult to confine the gases. Moreover, Avhen effective, the odor from 

 the dead rats is highly objectionable in occupied buildings. 



Chlorin, carbon monoxid, sulphur dioxid, and hydrocyanic acid 

 are the gases most used for destroying rats and mice in sheds, ware- 

 houses, and stores. Each is effective if the gas can be confined and 

 made to reach the retreats of the animals. Owing to the great dan- 

 ger from fire incident to burning charcoal or sulphur in open pans, a 

 special furnace provided with means for forcing the gas into the com- 

 partments of vessels or buildings is generally employed. 



Hydrocyanic-acid gas is effective in destroying all animal life in 

 buildings. It has been successfully used to free elevators and ware- 

 houses of rats, mice, and insects. However, it is so dangerous to 

 human life that the novice should not attempt fumigation with it, 

 except under careful instructions. Directions for preparing and 

 using the gas may be found in a publication entitled Hydrocyanic- 

 acid Gas against Household Insects, by Dr. L. O. Howard.^ 



Carbon monoxid is rather dangerous, as its presence in the hold of 

 a vessel or other apartment is not manifest to the senses, and fatal 

 accidents have occurred during its employment to fumigate vessels. 



Chlorin gas has a strong bleaching action upon textile fabrics, and 

 for this reason can not be used in many situations. 



» Circular 46, Bureau of Entomology, U. S. Dept. of Agric, 1907. 



369 



