WATER BEETLES IN RELATION TO PONDFISH CULTURE. 
233 
With our present meager knowledge outside of the Hydrophilidae it is not safe 
to name the larvae and pupae of any species, even tentatively, by basing our judg- 
ment on the known farm a of the pond from which the specimens were taken, on 
their size, or on any likeness they may show to European forms. All but one of 
the species here presented has been reared from the larva to the imago, thus making 
its identity certain. 
LAKES VERSUS FISHPONDS. 
Attention should be called to one very pronounced difference between the 
fauna of a lake and that of an ordinary fishpond. In the former water beetles 
are almost entirely lacking; in the latter they are one of the most abundant groups 
present. 
Muttkowski (1918, pp. 413, 414), in discussing the fauna of Lake Mendota, said: 
With all their manifold adaptations to an aquatic life, aquatic beetles, except for a few species, 
are scarce in the lake complex * * *. The Hydrobiidae, Dytiscidae, Hydrophilidse (except Berosus), 
Donaciinse, and Gyrinidse, the latter despite the water-breathing larvae, are practically absent from the 
lake community. The typical lake Coleoptera are the Haliplidae in the vegetation zone and the Dry- 
opidae in the rocky and gravelly areas, while several species of adult Dytiscidae are locally abundant 
* * *. The difference between the lake and other aquatic communities is very marked in late sum- 
mer, when sheltered water, such as the lagoons in the parks and the several ponds and creeks about the 
lake, teem with young dytiscid larvae of several species, while such larvae are conspicuously absent 
from the lake. 
Baker (1916, p. 308), in his discussion of the relations of mollusks to fish in 
Oneida Lake, N. Y., gave a list of the plants and animals found associated with 
the mollusks. There were included only two species of dytiscids, one haliplid, 
three gyrinids, and two hydrophilids. Of these, two species were found only in 
the stomach of the painted terrapin, leaving six species for the fauna of a lake 21 
miles long and 5.50 miles wide. 
Sherman (1913, p. 44), in summing up the habits of the Dytiscidae, said: 
In the larger bodies of water it is very difficult to locate any beetles, and in them, whether swamps, 
ponds, or rivers, the beetles seem to occur only in very limited spots, which are usually separated from 
the main sheet of water, such as the eddies or small pools along the shore. In fact, the small water 
bodies are always best, and the time most favorable for collecting is when the water is low or almost 
dried up. 
In marked contrast to this scarcity in large bodies of water is the abundance 
of beetles in the smaller ponds. The largest of the Fairport ponds is but a trifle more 
than an acre in area, and yet in the fauna of them all beetles are among the most 
numerous insects both in number of species and in individuals. Pond 5D, just 
an acre in area, yielded 39 species, while 2E, only 0.13 of an acre, contained 31 
species, and 12B, less than 0.02 of an acre, contained 17 species. 
METHODS. 
All the different beetle larvae that could be obtained were first studied in detail 
until they could be easily recognized. When the larva leaves the water in order 
to pupate, it either buries itself in the mud or constructs a pupal chamber, and on 
transforming throws off the old larval skin. As a part of this skin the chitinous 
covering of the head remains entire, with the antennae and mouth parts still 
