206 Trans. Acad. Sci. of St. Louis 
some which came as visitors remained at the bank to 
nest. It is this latter group which prevents one from 
definitely drawing the line between visitors and resi- 
dents; the parents of all the occupants must at one time 
have been visitors, but not all visitors were occupants. 
Reptiles. 
On October 3 I noted a snake (Fig. 16) at:the base of 
the bank, with a small portion of its body still within 
the rodent burrow, which I suspected was its home. It 
lay all day long in one position, as figured, but escaped 
when I attempted to capture it. At that season of the 
year, with food scarce, it probably had to wait a long 
time for a morsel, but if this creature had its home at 
the base of the clay bank all summer, it was no doubt 
a considerable factor in the control of the insect popula- 
tion during the season. 
Common lizards or swifts. 
During the entire summer of 1917 several common 
gray lizards made their home among the piled wood on 
top of the bank, and were undoubtedly a factor in reduc- 
ing the life of the group. They, too, had enemies, prob- 
ably larger ones, which I was unable to discover, and 
these all attacked the lizards in the same way, in the 
cases observed. During the summer, three dying lizards 
were found there at different times, all with torn ab- 
domens and entrails protruding, as shown in Fig. 17. 
They were always found in the early morning hours, 
which indicated that the attack had been made during 
the dark hours of the night. 
It was strange that these gray lizards did not appear 
