56 AX ECONOMIC STUDY OF FIELD MICE. 
OTHER MECHANICAL DEVICES. 
Mechanical methods of destroying voles have long been in use, ant 
sometimes are effective. In some countries where the animals are 
abundant, considerable reliance is placed upon the efforts of laborers 
armed with spades and other digging tools and assisted by dogs. In 
this manner thousands arc sometimes killed. 
Trenching also is a favorite method of catching both mice an< 
moles. Trenches a foot and a half deep are dug at intervals about th( 
infested lands. They i re Avider at the bottom than at the top, or ha 1 
perpendicular sides. The animals fall into these pits and are unabh 
to climb out. Men and dogs regularly make the rounds and despatcl 
the animals thus caught. This method was used effectively in Deal 
and New Forests in 1813 and 1814 and in the later vole plagues o: 
Great Britain and central Europe. 
Inundation with water and fumigation with sulphur have been em 
ployed to some extent in killing field mice. All these mechanica 
methods involve much labor and are slow and often expensive. 
POISONING. 
As the laying out of poison for wild animals is attended by dangei 
to other animals and to human beings, it should never be intrusted to 
the ignorant or careless. In some countries the laying of poison 
forbidden by law, and several of our own States have enactment 
regulating the practice or forbidding it. The majority of States have 
no legislation prohibiting the use of poison, and the matter is usually 
left to the judgment of the individual farmer, to whom attaches re 
sponsibility for any damage that may result through his carelessness 
Strychnine. 
All things considered, strychnine is the most satisfactory poison for 
field mice. Although a very deadly substance, it is less dangerous to 
handle than either phosphorus or potassium cyanide. Its extreme 
bitterness renders it less liable to be mistaken for a harmless drug. 
Nevertheless, every precaution should be taken in handling it. The 
strychnine salt most used commercially is strychnia sulphate. This is 
the best for poisoning purposes, since it is soluble in boiling water, 
while the alkaloid requires the presence of an acid for its solution. 
To disguise the bitterness of the poison when employed for rodents, 
sugar is used, or the strychnine may be mixed with its OAvn bulk of 
commercial saccharine. 
For poisoning field mice various baits ma} 7 be recommended, such 
as wheat, oatmeal, and corn, among the grains, and seeds of various 
plants, as the tomato, dandelion, sunflower, and others. The bait 
should be soaked over night in a poisoned sirup, which may be pre- 
pared as follows: 
