Hydro philidac 451 



Family hydro philidae 



HYDROPHILIDAE* 



METHODS OF COLLECTING 



THE majority of these beetles live at the water's edge and, if the soil, 

 grass, or other vegetation is stirred rapidly or washed briskly with 

 the water, the Hydrophilidae will soon be released and will come to 

 the surface. They may then easily be gathered by the hand. They do 

 not become submerged immediately as do the Dytiscidae, but swim 

 about on the surface until they regain shore or find some plant to aid 

 them in descending. An examination of the banks adjacent to the 

 collecting grounds at the time of transformation will offer good collect- 

 ing because often the larval skin, pupal skin, and the adult may be pro- 

 cured in the pupal cell at one time. Some of the species are attracted by 

 arc lights during warm nights and, in fact, it is there that Hydrous is 

 most frequently obtained. 



METHODS OF REARING 



The isolation, according to species, of adults, which readily lay eggs 

 in captivity, proved the best method of acquainting oneself with the 

 immature stages. Newly hatched larvae are thus easily obtained. The 

 most advisable temporary aquarium for such work seems to be a small 

 stender dish. A small stone, half submerged in the water and draped 

 with Cladophora gave excellent conditions for egg laying, especially for 

 smaller beetles which, as a rule, lay their eggs in moist places and not 

 directly in the water. 



For larvae, larger containers produce better results. Moreover, they 

 should be arranged as aquaria-terraria, for many of the adults and larvae 

 spend most of their time on shore. In preparing this, it is best to get 

 some mud from the bottom or edge of a pool and, after placing it in the 

 container to the depth of about an inch, slope it up gradually so that it 

 forms a miniature bank. The bank end should normally be high enough 

 so as to be a little dry on the surface. Cladophora and money-wort make 

 the best plant materials because of their cleanness and lasting qualities. 

 As a rule, the container should be filled so that the bank is covered and 

 then placed in the sun. In a few days, the time depending on the con- 

 ditions in the pool where the mud was obtained, numerous entomostra- 

 cans destined to be food for the future larvae will be present. The vege- 

 tation is then added. 



The larvae, when fully grown, seem restless and try to crawl out. If 



♦Abstracted from an article in Bull. Amcr. Mus. Nat. Hist. 42:1, 1920, by E. Avery 

 Richmond, Pennsylvania State College. 



