June, 1919] 



Fauna of Rock Bottom Ponds 



455 



species were insects. The other inhabitants were rather evenly 

 distributed through five groups. In these groups plankton and 

 pelagic types were by far the most numerous. 



TABLE 17. 

 Summary of Species in Ten Year Pond. 



Group 



Species 



Station 



Goleoptera 



Hydroporus concinnus . 

 Agabus disintegratus . . 



Diptera larvEe 



Chironomus dux 



Chironomus modestus. 

 Psychodid 



Ephemeridse 

 nymphs 



Heptagenia variabilis . 

 Blasturus sp 



Hemiptera 



Gerris conformis . 



Tricoptera 



Polycentropus sp . 



Entomostracan 

 Crustacea 



Cypris sp 



Asellus attenuatus. . . . 



Diaptomus sp 



Cyclops ater 



Bosmina lonc^irostris . 

 Nauplius (cyclops) . . . 



Mollusca 



Physa heterostropha. 



Planorbis parvus 



Ancvlus shimeki 



Annelida 



Glossiphonia stagnalis 



Glossiphonia nepheloidea. 



Rotifera 



Cathypera luna. ... 

 Triarthra longiseta. 

 Rotifera neptunis . . . 



Nemathelminthes 



Nematode. 



Coelenterata 



Hydra fusca . 



Protozoa 



Pleodorlna sp 



Ceratium longicorne. 



Chilomonas sp 



Euglena viridis 



Vertebrata 



Lepomis cyanellus . 

 Ameiurus na talis. . , 

 Tadpole (Rana) 



Algae 



Merismopedia . 

 Pediastrum. . . 

 Scenedesmus . . 



Total number of species . 



19 



The only forms which were well represented in point of 

 numbers were the midges and the mayflies. Two factors are 

 probably mainly responsible for the scarcity of other species. 

 The fishes are the factor operating to reduce the pelagic insect 

 population, whereas the almost total absence of vegetation and 

 debris may be held accountable for the poor representation in 

 other groups. 



