232 



BULLETIN OF THE BUKEAU OF FISHERIES. 



Systematic description of Fairport species — 



Continued. Page. 



Thermonectes 291 



T. basilaris 291 



T. ornaticolHs 296 



AciUus 299 



A. semisulcatus 299 



Dineutes 302 



D. americanus 302 



Gyrinus 308 



G. ventraHs 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. pcge. 



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 (Haliplidse) , 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. 



