PHYSIOLOGICAL ANIMAL GEOGRAPHY 569 
turn toward the observer. They almost never alight on vege- 
tation. When caused to fly up from a narrow path, they fre- 
quently fly in a circle and return to a point behind a person moving 
forward. I have never seen them crawl under objects when pur- 
sued. They excavate burrows for the night and cloudy days. 
2. Kcological relations. a. Area of special study. They 
have been studied specially at the south end of Lake Michigan. 
Here the species is found only on the ridges with pines. These 
ridges were originally thrown up under water near the shore. 
By the falling of the surface of the lake, which has amounted to 
a total of 18 meters since glacial times, ridges have been left out 
of water perhaps about as fast as they were formed. We have, 
then, a series of them of different ages, arranged in order of age. 
The youngest are nearest to the shore. Their width varies from 
five to thirty meters. Long, narrow ponds of corresponding age 
occur between the ridges. As a given ridge came above the sur- 
face of the water, it often received wind-blown sand; there is little 
or no vegetation on the youngest ridges. 
b. Local distribution. C. tranquebarica is absent from the 
ridges with sparse vegetation. On the ridges on which young 
conifers are found together with various herbaceous plants along 
the pond margins, C. tranquebarica is present. Adults are nu- 
merous along the margins of the ponds and all over the ridges, 
particularly on the sandy ‘blowouts,’ or points where the wind has 
removed some of the sand and keeps the vegetation from growing 
up. The beetles frequently burrow into the sand for the night 
and for hibernation. Food is abundant on the white sand areas 
and the beetles find advantage in its conspicuousness, which no 
doubt causes them to congregate on these places to feed. 
When an area of denuded sand, in which ponds or depressions 
are present, is deposited or exposed, vegetation appears first 
nearest the water. Humus accumulates, blackening the soil and 
making conditions favorable for more plants, so that a turf is 
soon formed near the water. Similar processes are going on higher 
up on the side of the pond margin and it is soon captured by the 
plants. It is on the ridges in which the soil just above the very 
moist or sedge zone is blackened by humus, but still not completely 
occupied by the roots of plants, that we find C. tranquebarica. 
