14 MAMMALS IN THEIR EELATION TO SPOTTED EEVER. 



Fig. 4. — Columbian ground squirrel 

 (Citellus columhiamis) . (About g 

 natural size.) 

 [Cir. 821 



150 and 200 " picket pins " were 

 examined, and practically all those 

 taken in good " tick country " were 

 found to serve as hosts for the 

 younger stages of Dermacentor 

 venustus. On many of them were 

 several dozen nymphs or seeds; 

 from one, 62 nymphs were taken, 

 and from another over 100 seeds.- 

 No adult ticks were found on them. 

 It is probable that this ground 

 squirrel raises more young fever 

 ticks than does any other species, 

 possibly more than all other species 

 of animals combined. Nymphs and 

 seeds were found on ground squir- 

 rels taken from under stables and 

 unoccupied cabins, and it is prob- 

 able that they often drop engorged 

 ticks under such buildings. The 

 fact that practically 100 per cent of 

 these squirrels artificially infected 

 with spotted fever in captivity 

 have contracted the disease in mild 

 form is significant. 



One of the most important and 

 fundamental steps in the control of 

 the fever is unquestionably a deter- 

 mined and concerted effort to 

 lessen the number of picket pins, 

 especially in pastures and around 

 dwellings. These animals are so 

 destructive to crops that any ex- 

 pense incurred in destroying them 

 will be well repaid by the resulting 

 freedom from their depredations. 



* SIDE-STRIPED GROUND SQUIRREL. 



(Callospermophihis lateralis cmerascens.) 



The little side-striped ground 

 squirrels are abundant on the lower 

 slopes of the mountains on both 

 sides of Bitterroot Valley through- 

 out its length. They seem to prefer 



