PHYSIOLOGICAL ANIMAL GEOGRAPHY 561 
The steepness of the slope makes conditions severe for plant life. 
It is only where inactivity of forces of erosion has decreased the 
steepness of the slope, that scattered plants are present. Where 
the slope is still less steep, the bluff is sometimes covered with 
forest. 
On the upland adjoining the bluff are stretches of meadow, 
woods, and sometimes pastures, all intersected by paths, roads, 
and ravines. All these furnish bare ground which apparently 
is essential to these tiger beetles. At the base of the cliff is fre- 
quently found a narrow stretch of sandy beach, which varies in 
width from 1 to 25 meters (figs. 7, 8 and 9). 
b. Loeal distribution. The adult beetles of C. limbalis are 
found on the upland near the bluff in all of the bare places just 
Fig. 10 The burrow of C. purpurea limbalis; p.c., pupal cell. One-third 
natural size. 
described, and on the steep clay bank and the sandy beach— 
about equally distributed in proportion to the area of the bare soil 
exposed (figs. 7, 8, 9). If the number be greater in any one of 
the situations, it is on the sandy beach. If the adults be about 
equally distributed on the different areas, which of these are we 
to consider the habitat of the species? Let us inquire into the 
habits of the larvae. 
3. Ecological relations of the larvae. a. Local distribution. 
I have carefully watched the larvae of this species (fig. 10) in 
their external environmental relations for five years in the vicinity 
of Glencoe. They are found almost exclusively on the clay 
bank (fig. 11). Occasionally larvae are found in bare places on 
the steep banks of the ravines. Three or four individuals were 
once found on the top of the bluff in a bare place on level ground, 
