BIOLOGICAL SURVEY. 239 



JACK RABBITS. 



Demonstrations were held and campaigns organized during the 

 winter to combat jack rabbits in infested farming communities of 

 southern Idaho, central and eastern Oregon, southwestern Utah, 

 northern Nevada, western Texas, and in smaller areas in California. 

 Snowshoe rabbit repression was also undertaken on the Manti 

 National Forest of Utah. Weather conditions were favorable for 

 successful poisoning operations and a great number of these very 

 destructive pests were thus disposed of. Many communities were 

 organized for systematic campaigns for the coming winter. 



PRAIRIE-DOGS. 



Prairie-dog repression has been carried on with exceptional vigor, 

 and the areas freed of this pest on National Forests and other public 

 domain during the past fiscal year were more than double the total 

 area of previous years. From July 1 to the end of the season 1915, 

 heavily infested Government land had been poisoned to the extent of 

 886,429 acres, and 164,755 acres previously poisoned had been gone 

 over a second time. From the opening of the poisoning season in 

 April to June 30, approximately 470,000 acres were treated, making 

 a total of 1,356,429 acres of Government land covered during the 

 fiscal year. Of this area 504,393 acres are public lands of eastern 

 Wyoming and southwestern South Dakota, and the remainder is on 

 National Forests in Arizona, New Mexico, Colorado, and Montana, 

 including the Crow Indian Reservation of Montana. The cost of 

 this work varies from 1 to 2 cents an acre in the more lightly 

 infested areas, from 6 to 8 cents an acre where the prairie-dog holes 

 run from 10 to 20 to the acre, or an average of 5 cents an acre. The 

 efficiency of the poison used has averaged from 85 to 90 per cent for 

 one application. Mortality following the use of the poison in the 

 northern States has been much higher, however, being placed at 98 

 per cent after a careful examination of the areas covered on the 

 Custer National Forest and the Crow Indian Reservation of 

 Montana. 



POCKET GOPHERS. 



During the fall, 5,390 acres of very heavily infested areas of fine 

 grazing lands were cleared of pocket gophers on the Ochoco National 

 Forest of Oregon, and also 1,280 acres on the Sequoia and 1,100 acres 

 on the Tahoe National Forest of California. Methods of controlling 

 this pest were demonstrated among farming communities in Tulare 

 County, Cal. ; in the Rio Grande Valley, Tex. ; and in the Mescalero 

 Apache Indian Reservation, N. Mex. 



LAND CRABS. 



Experiments to determine economic methods of controlling land 

 crabs were conducted in the vicinity of Cocoanut Grove, Fla. These 

 pests were estimated to have destroyed 60 per cent of the tomato 

 plants of the locality, as well as quantities of other garden truck. 

 They also damage coconut groves by their numerous burrows. It 

 was found that the crabs could be exterminated by introducing 5 



