THE CANADIAN ENTOMOLOGIST 175 



All I could identify were constricta, and I felt satisfied that they 

 would have appeared in much larger numbers had the weather 

 been favorable. The Holland River is the principal source of 

 Lake Simcoe and winds for many miles through wide prairie-like 

 stretches of open marsh. I believe, therefore, that this river is 

 the chief breeding-place for both species of ^shna S/ud that the 

 vast majority of individuals which spread over the countryside 

 during their foraging excursions, ultimately return there to oviposit. 

 I received reports of the occurrence of immense numbers of large 

 dragonflies, presumably i^shnas, from the neighbourhood of Big 

 Bay Point, almost ten miles north of De Grassi Point, and I am 

 strongly of the opinion that these also came in large measure from 

 the Holland River. ' 



On the basis of this habit of wandering many miles from their 

 breeding-places an explanation may be offered of the prevalence 

 of these species of /Eshna at De Grassi Pt. and other localities 

 during warm seasons, and their scarcity during cool seasons. Warm 

 weather induces activity in dragonfiies and on hot, sunny days 

 yEshna is frequently in almost ceaseless flight, while in cool, dull 

 weather it scarcely flies at all. Hence, in warm seasons they 

 spread to localities, more or less remote from their breeding-places, 

 which under other conditions they do not reach at all. It is thus 

 qufte probable that the actual number of dragonflies which emerge 

 from their breeding-places is not appreciably affected by the 

 temperature of the surrounding air. It is also possible, however, 

 that their numbers after emergence may be more rapidly decimated 

 by their enemies in cool seasons than in warm, owing to their 

 relative inactivity under these conditions. 



The nomadic habits of i^^shna may also be illustrated by the 

 following instances of occasional or sudden appearances at De Grassi 

 Point of species of this genus, other than canadensis and con- 

 stricta. 



On Sept. 9, 1916, I spent part of the afternoon at Wilson's 

 Creek, watching the ^^shnas patrolling the marshy banks of the 

 stream near its mouth. I had supposed they were all canadensis, 

 but on capturing one I was surprised to find that it was A. eremita 

 Scudd, a common northern species, which I had never taken here 

 before. My next capture was also eremita, both being old males 



