232 
BULLETIN OF THE BUREAU OF FISHERIES. 
Systematic description of Fairport species — 
Continued. Page. 
Thermonectes 291 
T. basilaris 291 
T. ornaticollis 296 
Acilius 299 
A. semisulcatus 299 
Dineutes 302 
D. americanus 302 
Gyrinus 308 
G. ventralis 308 
G. limbatus 308 
Berosus 309 
B. striatus 309 
B. pantherinus 311 
B. peregrinus 312 
Hydrophilus 314 
H. obtusatus 314 
Systematic description of Fairport species — 
Continued. p Bge . 
Laccobius 315 
L. agilis 315 
Enochrus 316 
E. nebulosus 318 
E. diffusis 320 
E. perplexus 321 
Tropisternus 321 
T. lateralis 321 
T. glaber 326 
T. mixtus 329 
Hydrous 332 
H. triangularis 332 
Donacia 332 
D. sequalis 332 
Cap attachment on egg case 332 
Bibliography 334 
INTRODUCTION. 
IMPORTANCE OF WATER BEETLES. 
The beetles are far more numerous than any other order of insects and are 
very cosmopolitan in their distribution. Every natural pond, river, and stream 
is peopled with them, and if one constructs an artificial fishpond in all probability 
beetles will constitute its first and most permanent insect inhabitants. Pondfish 
culture, therefore, in order to prove successful, demands sufficient acquaintance 
with the water beetles to yield a workable knowledge of their economic relations 
to the fish. The following paper is a beginning toward such an acquaintance and 
endeavors to suggest lines of research that may prove both interesting and profit- 
able to the fish-culturist. 
IGNORANCE OF AMERICAN SPECIES. 
Unfortunately, while our American water beetles are fairly well known to the 
systematist, so that they appear in museum collections and lists of species, very 
little is known about their life histories, their habits, and their economic impor- 
tance. According to Comstock (1912), at least 300 species of carnivorous diving 
beetles (Dytiscidse) occur in this country, 40 species of whirligig beetles (Gyrinidae), 
and 150 species of water scavenger beetles (Hydrophilidae). Moreover, there are 
25 species of herbivorous water beetles (Haliplidae) , a family only briefly mentioned 
by Comstock. Out of this total of more than 500 species, which is probably far 
below the actual number, the habits and complete life histories of only about 20 
are known. The partial development of 15 other species has been recorded, chiefly 
the egg cases and newly hatched larvae of hydrophilids by Richmond (1920). This 
excellent paper also gave valuable keys for the identification of the egg cases, larvae, 
and pupae of the Hydrophilidae, but nothing of the sort has been published for the 
other families. 
Abstracts of one or two of these published life histories, which are important 
from the standpoint of fish culture, are included in the present paper, and in addi- 
tion those of 20 other common species are presented, together with the economic 
relations of the entire group. 
