12 



farmers' bulletin 932. 



«»or " s(iiiirrels aiul ''picket pins.'- They iiiliabit mainly open plains, 

 mountain valleys, and borders of wet meadoAvs, but are found also 

 in open places in the forests and sometimes high up the slopes of 

 mountains. They dig numerous deep burrows and are very de- 

 structive to nearly all crops (fig^^. 8 and 9), eating both the growing 

 plants and the ripe or ripening grain. In irrigated districts the 

 animals burrow in embankments (fig. 10) and levees and are almost 

 as troublesome as pocket gophers. 



Among the largest and most destructive of these animals is the 

 California, or *' digger," ground squirrel.^ It is gray in color and 



B9I4I 



Fig. S. — Cornfield ruined by Columbia ground squirrel-s (see title-page illustration). 



has a long, rather bushy taiL It occurs in the Southwest and West 

 from western Texas to California and Oregon.^ In parts of Cali- 

 fornia the race known as the Beechey ground squirrel is especially 

 abundant and menaces not only crops and irrigation ditches, but also 

 human life, in that it is a known carrier of bubonic plague. About 

 a dozen cases of this disease among human beings have been traced 

 directly to this squirrel and a large number of the animals collected 

 by the United States Public Health Service have been found in- 

 fected. The Health Service, in cooperation Avith State authorities, 

 has succeeded in establishing south and east of San Francisco, in the 



^ Citcllus 'beccheiji heecheyi and related races. 



2 Including the closely i-elated Citellus grammurus. 



