786 



THE MONTHLY BULLETIN. 



absorbent ball about the size of a hen egg is made of jute wrapped in 

 cheesecloth. Place about 65 of these in a vessel and pour over them 

 one gallon of the carbon disulphid. As the liquid is very volatile, it is 

 necessary to have a lid on the vessel which fits tightly. Drop one of 

 these saturated balls into each burrow and after two minutes light 

 with a match or torch, being careful to keep the face away from the 

 opening. Then tightly close up the burrow. The cost of treating an 

 area the first time with the carbon disulphid is greater than with the 

 poisoned grain; however, the percentage of animals killed is usually 

 higher, which offsets to some extent the difference. ' It is good for 

 follow-up treatment after using poisoned grain. A combination of the 

 two methods is often cheaper than either used alone. 



Similar investigations have been made by the Biological Survey in 

 California on the problems of controlling pocket gophers, jack rabbits 

 and other destructive rodents, and reliable methods have been devised. 

 In the case of pocket gophers, the main difficulty lay in placing the 

 poison where the animal would find it. A close study of the habits 

 of the animal and its underground home has resulted in a method so 

 practical and effective that these costly pests can be quickly eliminated 

 from any given area. 



RECORD OF OPERATIONS IN CALIFORNIA. 



Minor operations against squirrels, gophers and seed-eating rodents 

 were carried on in California from 1911 through 1912 on the Tahoe, 

 Santa Barbara, Angeles and Shasta national forests. The season of 

 1913 marks the beginning of the extensive work in this state against 

 ground squirrels on the Monterey, San Benito, Santa Barbara and 

 Sequoia national forests. From this time on to the present season the 

 operations have steadily grown in extent until some of the forests have 

 now been entirely covered once and parts retreated a second and a third 

 time to complete extermination. The California forest has been prac- 

 tically entirely treated, also the more heavily infested areas of the 

 Modoc, Sierra, Sequoia, and Monterey forests. Extensive work on the 

 Santa Barbara forest and the outlying public lands in San Luis Obispo 

 County are planned for the coming season. 



The total acreage treated for ground squirrels on the various forests 

 and public lands in California up to the beginning of the 1918 season 



is as follows: 



California National Forest 446,385 



Modoc National Forest 53,000 



Monterey National Forest 37,000 



Sequoia National Forest _ 93,645 



Sierra National Forest 7,607 



Santa Barbara National Forest 11,525 



Tule Indian Reservation 3,700 



Public Lands in San Benito County 4,610 



For Pocket Gophers. 



Sequoia National Forest 1,280 



Tahoe National Forest 1,100 



659,852 



194 



