LLUSTRATIONS. 
PLATES. 
Page. 
Plate I. Ticks and spotted fever in the Bitter Root Valley, Montana. Fig. 1. — 
View in Lo Lo Canyon, which leads into the Bitter Root Valley, 
showing conditions under which ticks thrive. Fig. 2. — Camp 
laboratory near Florence, Mont., in one of the most heavily in- 
fested localities known 8 
II. The Rocky Mountain spotted-fever tick (Dermacentor venustus). 
Fig. 1. — Adult female unengorged, dorsal view. Fig. 2. — Adult 
male, dorsal view. Fig. 3. — Adult female unengorged, ventral 
view. Fig. 4. — Adult male, ventral view. Fig. 5. — Adult female 
in act of depositing eggs 20 
III. Spotted-fever tick (Dermacentor venustus) and Dermacentor albipictus. 
Fig. 1. — Adult spotted-fever tick which has deposited eggs. Fig. 
2. — Larva of spotted-fever tick. Fig. 3. — Engorged nymph of 
spotted-fever tick. Fig. 4. — Same, ventral view. Fig. 5. — Adult 
male of Dermacentor albipictus. Fig. 6. — Adult female of Derma- 
centor albipictus, unengorged 20 
TEXT FIGURES. 
Fig. 1. Map showing area in which the spotted-fever tick occurs 16 
2. Diagram showing possible seasonal history of spotted-fever tick 27 
3. Dipping vat 38 
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