AQUATIC INSECTS IN THE ADIRONDACKS 



491 



to T e t r a g o n e 11 r i a is, therefore, an inference : it is sufficiently justi- 

 fied by the following considerations. 



i) Tetragoneuria was the only Hbellulid sufficiently common at 

 the pond to have produced the enormous number of eggs observed there. 

 I think one might easily have filled a barrel with the clusters that could 

 have been picked up at the surface of this pond : the cluster shown in 

 the figure (which was smaller than the average) contained about 110,000 

 eggs (counted in part, and estimated), and with its enveloping gelatin 



Fig. 19 Eggs of Tetragoneuria hung on submerged twigs near surface of the water 



would have about filled a half pint measure. These clusters are doubtless 

 the work of a number of females ; the separate strings are often indicated 

 by the ends left hanging free. These are undoubtedly libelluhd eggs : none 

 of our larger Libellulinae lay their eggs in strings; nor do the smaller 

 Cordulinae, but the European genus E p i t h e c a , not distantly related 

 to Tetragoneuria, does so. 



No other Cordulinae were common at this pond. I did not get more 

 than a single nymph or imago of any other save Cordulia shurt- 

 leffi, and of that less than a dozen in all, there. But Tetragoneurias 

 were abundant above all that I have ever seen elsewhere. They were 

 scattered all about the margin excepting, perhaps, the bare shores of part 

 of the north side, and were apparently rather uniformly distributed. I 

 counted the number of cast skins of Tetragoneuria, without regard 

 to species, clinging to the thin grass tussocks and fallen twigs along the 

 water's edge for a distance of several rods at two places : at the north 



