66 RODENTS OF IOWA 



its bulk of barium carbonate and sufficient water to form a thick 

 dough is easily handled and distributed. The poison may also be 

 fed in the form of a dough made of four parts flour or meal to one 

 of the poison. It may also be spread upon moistened toast, fish, or 

 bread and butter. Such baite may be placed in small pieces along 

 and in the runs. If the first application does not bring the desired 

 results another bait should be tried. This poison has a corrosive 

 action upon the stomach lining. 



Powdered white arsenic (arsenious acid) has long been used as 

 a poison for rats, but while some rats may be killed by it others 

 will survive and once recovered they will seldom be attracted a 

 second time. The baits mentioned above for use with barium car- 

 bonate or strychnin may be used with arsenic. A successful method 

 of using this poison is to take twelve ounces of corn meal and one 

 ounce of the arsenic to which are added the whites of enough eggs 

 to form a heavy dough. 



Phosphorus is a commonly used poison, and the writer has used 

 it with a considerable degree of success. However, the phosphorus 

 pastes which may be obtained at the drug stores vary to such 

 a great extent in the proportion of phosphorus present that they 

 can scarcely be relied upon, while in some the amount of phosphorus 

 present renders the paste highly inflammable. Home-made prepara- 

 tions are liable to result in conflagrations. Phosphorus paste does 

 not prevent decomposition of the body of the animal which has 

 eaten it, neither do the animals leave the premises before dying. 

 On the whole phosphorus paste is not a satisfactory poison for ro- 

 dents, and its use in this respect is not encouraged. 



Where rats infest buildings and yards occupied by poultry the 

 poisoned baits may be placed in a small wooden box over whieh is 

 set a considerably larger box, bottom upward, with one or more 

 holes in the sides sufficiently large to admit the rats. The pests 

 thus have access to the poison whil the fowls cannot reach it. 



Fumigation with carbon bisulphid is effective in destroying rats 

 in burrows in fields and along river banks and levees. Carbon 

 bisulphid is a highly inflammable liquid which evaporates rapidly 

 upon exposure to the air and gives off a poisonous vapor. It can 

 be used in fumigation only where the fumes can be confined suf- 

 ficiently so that the animals are asphyxiated, and for this reason is 

 not effective in most buildings. To fumigate rat burrows take a 

 wad of cotton or other absorbent material, saturate thoroughly with 

 the liquid and push into the burrow as far as possible with a stick. 



