264 
BTT T.T.E TTN OF THE BUREAU OF FISHERIES. 
Distribution in the Fairport (Iowa) fishponds according to beetle families. 
Pond number and 
series. 
Hali- 
plidae. 
Dytis- 
cidae. 
Gyrini- 
das. 
Hydro- 
phuidae. 
Total. 
Pond number and 
series. 
Hali- 
plidse. 
Dytis- 
cidae. 
Gyrini- 
use. 
HydrO- 
philidse. 
Total. 
12B 
2 
6 
! 
8 
17 
7D 
4 
,12 
3 
9 
28 
13B 
2 
2 
2 
5 
11 
8 D 
4 
12 
3 
7 
26 
I4B 
2 
5 
1 
5 
13 
9D 
3 
1 
4 
11 
15B 
2 
2 
1 
5 
10 
IE 
2 
7 
1 
5 
15 
16B 
2 
5 
1 
8 
16 
2E 
4 
15 
3 
9 
31 
ID 
3 
7 
0 
5 
15 
3E 
3 
11 
3 
10 
27 
2D 
3 
13 
3 
13 
32 
4E 
3 
10 
3 
5 
21 
3D 
3 
10 
3 
9 
25 
IF 
2 
3 
3 
4 
12 
4D 
3 
4 
12 
2F 
2 
6 
6 
17 
5D 
6 D 
4 
1 
18 
0 
3 
14 
4 
39 
3F 
1 
4 
2 
5 
12 
SOURCE OF MATERIAL. 
In the summer of 1916 Geo. B. Lay collected and identified the various insect 
forms found in the Fairport fishponds, and in 1917 Dr. R. A. Muttkowski checked 
the species thus obtained and, with Mr. Lay, completed their identification. Both 
made out reports of their work, containing in addition to the check list some notes 
on the habits of certain of the insects in relation to fish breeding. The writer 
has used their check list in its entirety as the basis of the one here presented, 
chiefly because it was prepared during the same years that Mr. Schradieck was 
listing the food of the fish and Dr. Emmeline Moore was studying the plant fauna 
of the ponds. For this reason the beetle list, the plant list, and the fish-food list 
exactly supplement one another. The first shows the kinds of beetles found in the 
ponds from which the fish were taken, the second explains the relative abundance 
of the beetles in the different ponds on the basis of their plant environment, and 
the third indicates the choice the fish made of the beetles that were available. 
Every species in this beetle list has been verified by the present author during 
the years 1918, 1919, and 1920, and to it have been added other species that either 
escaped capture in 1916 and 1917 or have appeared more recently in the pond 
fauna. These additions are indicated by a star (*) following the species name and 
include only two forms that are anything more than occasional interlopers, namely, 
Hdli'plus borealis and Thermonectes ornaticollis. 
INFLUENCE OF ENVIRONMENT. 
Dr. Muttkowski called attention in his report to the remarkable difference in 
both the quantity and the quality of the population of the various ponds. This 
is the more noteworthy because of the contiguity of the ponds. Those in the same 
series are separated from one another by narrow banks of earth, 12 to 15 feet in 
width, and pond 4E is separated from pond 5D by a similar narrow bank. Pond 
6D is very small and is used as a natural aquarium in which to keep the large bass 
to prevent them from eating other fish. They are so hungry most of the time 
that they keep the pond cleared of all animal food throughout the summer. This 
accounts for the meagerness of its insect fauna, and it can not be fairly considered 
in comparison with the others. Ponds 1 and 2D are contiguous, are about the 
same size and depth, and are surrounded with the same vegetation. They were 
