266 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE. 
should not exceed 18 cents per acre, and should fall as far short of 
this, as possible. 
Amon^ the measures that succeed well enough on a small scale or 
under special conditions are trapping, drowning, destruction by 
domesticated ferrets, and capture in sand barrels and straw barrels 
placed over the holes. On a large scale, poisoning and fumigating 
have yielded the best results. 
POISOXING. 
By poisoning is meant the administration of a poison or combination 
of poisons by means of some article of food which the animals will 
readily eat. The poisons most in favor are strychnine and cj'anide of 
potassium. Phosphorus also has been used and is an ingredient of 
many of the poison mixtures sold in the stores. It is efficient, but its 
use is attended with danger, and it is not recommended by this Depart- 
ment. 
Cyanide of potassium.— Cyanide of potassium kills quickly, and is 
an excellent poison, but it is sometimes difficult to administer, chiefly 
on account of its odor, which is offensive to most animals. Like 
phosphorus, it is dangerous to man, and must l)e handled with great 
care. It is said to lose its power when wet or exposed to the atmos- 
phere. It has been administered in prunes and raisins, and (in combi- 
nation with strychnine) is a component of the celebrated Peters nux- 
ture for poisoning grain, in which it is disguised ]\v a coating of 
molasses, flavored with oil of anise. 
Strychnine. — Strychnine is probably, all things considered, the 
best and most satisfactory poison now known for the destruction of 
prairie dogs. It can he obtained everywhere, usually at a moderate 
price, and its use is simple. The minimum dose necessary to kill 
prairie dogs is not known, but it is safe to say that the quantity recom- 
mended in the Peters formula (3 ounces to a ])ushel of wheat) is exces- 
sive. Two ounces is doubtless sufficient, and 1^ ounces is probaljly 
enough. (For ground squirrels, 1 ounce to the bushel of grain is 
ample.) The str\xhnine sulphate should be dissolved in. v. arm water, 
in which the grain should be soaked for twenty-four or thirty-six 
hours, until all is absorbed. Some experimenters lind this sufficient: 
others prefer to sweeten the grain b}' stirring in a quart or two of 
molasses and sprinkling with enough corn meal to prevent sticking. 
Some use corn meal alone, made into pellets, without any whole grain. 
Another way to administer strychnine is to introduce small quantities 
in prunes or raisins, in pieces of apple, carrot, or turnip, or on bread 
and butter. In the last case it is said that the strychnine should 'be 
sprinkled on buttered bread and then coated lighth' with sirup, after 
which the bread is cut in small squares and placed around the burrows. 
The cost of strychnine sulphate, as customarily sold in small Western 
