THE LIFE OF DEVILS LAKE 99 



great difference in tolerance for salt concentration shown by various 

 species of both plants and animals in the Devils Lake complex, and 

 need not consider it further here. 



The stickleback occurs in both Main and Stump Lakes and 

 probably in other lakes of the complex, as well as in fresh waters. 

 It was formerly common in Main Lake, but appears to be much less 

 so at present. In the summer of 1914 several were found dying 

 in the lake, for a reason which could not be ascertained. The tem- 

 perature of the water at the time was not higher than probably oc- 

 curs frequently in lakes where the stickleback abounds, and bacteri- 

 ological examinations made a few hours after death gave no evi- 

 dence of pathogenic bacteria in the fish. 



In 1912 also the sticklebacks were found dead in large numbers 

 on shore in spring about the time of opening of the lake. The cause 

 of this fatality also is obscure. It is possible, altho it seems un- 

 likely, that the fish may have been trapped in the ice and frozen 

 to death. Lack of oxygen will hardly account for it, since it al- 

 ways appears to be ample, thru the greater part, at least, of the 

 water stratum. 



The freezing of a layer of water a metre thick in a lake only 

 6 or 7 metres deep necessarily causes a great concentration of salts 

 in the remaining water, and it is possible that the weaker stickle- 

 backs were unable to withstand this increased concentration; and 

 further that their death in summer may have been due to salt con- 

 centration, coupled with high temperature. 



In recent years their death has not been noted, altho they ap- 

 pear to be present in considerably diminished numbers. 



They breed in the Ruppia, nests with eggs having been found 

 during late June and early July. 



AMPHIBIA 



Two amphibians occur in Devils Lake, the pickerel frog (Rana 

 pipiens) and the salamander (Amblystoma tigrinum). 



The former of these is occasionally common about the edges of 

 the lake and has been taken in Stump Lake, while the latter is a 

 regular inhabitant of its waters. Neither species, so far as known, 

 breeds in the lake. 



The salamander was reported by Pope (1908) as Crytobranchus 

 allegheniensis, and later reported by me (Young 1912) as Ambly- 

 stoma. They occur both as larvae and adults. Some of the adults 

 are unusually large, measuring 25 to 28 cm in length. 



There are numerous small fresh water ponds, ditches and 

 swamps in the Devils Lake complex, which in spring are usually 

 full of water, and which probably serve as breeding grounds for 

 both frogs and salamanders. In one of these, near the south end 

 of Stump Lake, the salamanders breed abundantly. 



