82 . MARINE AND FISHERIES 



5 GEORGE v., A. 1915 



is at its height during the second week in July and is over before the end of the 

 month. July 23 is the latest date on which we have taken this species. 



N. yamaskanensis is abundant and of general distribution in this locality and 

 probably throughout the Muskoka and Parry Sound Districts. I have received 

 exuviae from various parts of Muskoka and from the Shawanaga and French Rivers, 

 collected by Mr. Paul Hahn. They are not known north of the French River. 



Epicordulia princeps (Hagen) Selys. 



This large insect is very common about Go Home Bay, where it is the species 

 most frequently observed flying far over the open water. 



The nymphs live among the bottom debris of shallow bays and inlets and the 

 larger ponds, associated with Tetragoneuria. They are quite often found clinging 

 to the undersides of stones. None were reared in 1907 but tenerals began to appear 

 on June 25 and in a few days became quite numerous. They appeared at the 

 same time in 1912, the first imagoes having been observed on June 26th, this being 

 also the date on which the first specimens emerged in the laboratory. In the first 

 week or so of their imaginal life, they no not fly very swiftly and rest frequently 

 so that they are easily captured, but later they wander far from their breeding- 

 places and during the day in fine weather they seem to be in constant flight from 

 early morning until dusk. During the evening they may be seen flying, usually 

 rather high, in pursuit of mayflies like Neurocordulia. 



This is one of the later Cordulines to remain on the wing, individuals being 

 met occasionally as late as Aug. 6. 



In specimens from Georgian Bay the dark wing markings are usually greatly 

 reduced as compared with specimens from the Upper Austral Zone (Toronto and 

 southward). While in some females these spots are almost as large as in southern 

 specimens, in the great majority of both sexes they are all much smaller. The 

 nodal spot is frequently a mere trace or it may be absent altogether, as indeed is 

 generafly the case in the males. The apical spot is also frequently a mere trace 

 and such individuals look much like large Tetragoneurias. 



Tetragoneuria spinigera (Selys) Selys. 



When we arrived at the station in 1907 (June 16) this species was already flying 

 in considerable numbers in the open woods of the mainland near a small lake, and 

 the season for emergence was apparently over, though that of T. cynosura simulans 

 had scarcely begun. We therefore watched for the appearance of spinigera in 

 1912 as we were at the Station before the period of emergence for either species had 

 begun. 



On May 29th a single Tetragoneuria exuvia was found on the shore of Big 

 Island and on June 1 we found large numbers of them clinging to the reeds and 

 floating on the water in the open marsh at the outer end of Galbraith Lake. No 

 imagos were found except a single crippled teneral with its exuvia. This was a 

 male, however, and could be diagnosed with certainty as T. spinigera. Much 



