THE LIFE OF DEVILS LAKE 95 



They probably occur in most of the lakes of the complex, but these 

 are the only records. 



Sympetrum corruptum breeds in Lake P, but apparently not 

 in other parts of the complex. 



Arctecorixa sp. Common and widely distributed in all lakes 

 of the complex and in fresh water. 



Corixa sp. A common species. Reported from Main, Stump, 

 East and Spring Lakes and Lakes A and P. 



Corixids are both thermo — and phototropic. I have found them 

 numerous in the open water along shore in spring, when most of 

 the lake was frozen and the shore water was several degrees warmer 

 than that beneath the ice. They are attracted by the light of a 

 lantern, but their manner of response appears to be that of trial and 

 error, not direct. 



They are present at all seasons of the year, but while occa- 

 sional in the plancton samples are not sufficiently numerous to ad- 

 mit of any definite conclusions regarding their seasonal distribution. 

 While occurring in all zones and at all levels, they appear to be more 

 numerous near shore and in the Ruppia zone. I have observ^ed them 

 copulating in August and September and have found immature 

 specimens in July and August. In a laboratory they do not live 

 long. Whether this is due to a natural bre\aty of life, or to the 

 artificial conditions of their environment I cannot say. 



Notonecta sp. Prior to 1914 the back-swimmer was occasionally 

 taken in Main Lake. It was present thru the summer and beneath 

 the ice in March. 



Notonecta undulata. Reported in Lake 0, also in fresh water. 



Biienoa niargaritacea. A single specimen from Lake P about 

 September 5, 1919, is the only record of this species. 



Triaenodes flavescens. Larvae were found in Lakes C, and 

 P and in fresh waters. 



Limnophilus rhomhicus L. This widely distributed species is 

 the commonest caddis fly in the region. Present in Minnewaukan 

 Bay and in fresh waters (1921). 



Phryganea sp. A few caddis fly larvae were found among 

 algae near shore in Main Lake in 1922 by my assistant, Miss 

 Stegenga. This record is of considerable interest because of the 

 very unusual occurrence of caddis larvae in other than fresh water.* 

 Apparently these larvae are not of regular occurrence in Devils 

 Lake, for this is the only record of their presence here. Larvae of 

 P. interrupta occur rather rarely in fresh water lakes in the vicinity 

 of Devils Lake. 



♦See p. 102. 



