THE CANADIAN ENTOMOLOGIST - 419 



colour of the insects is much Hghter than that of other species 

 of the same size so they may be easily recognized upon the wing. 

 From time to time females appear in the swarm. The male 

 chases the female in a spiral course, the two together appear like 

 a single individual. Instead of dropping down, as some species 

 do, they mate in their spiral course toward the summit of the column 

 where they are lost to sight. From the beginning of mating till 

 they disappear in the darkness it requires about 3 minutes. 



Oviposition and eggs. — Observations were made during the 

 night of July 30, 1915, on some captured individuals. Oviposition 

 took place about 5.45 a.m. The female alighted on a leaf of 

 Elodea, raising her abdomen by drawing the hind legs close to 

 each other, then flexed her abdomen with its tip pointing down- 

 ward. On touching the leaf surface several times with the tip 

 of the abdomen, some transparent globules were exuded. This 

 was repeated after short intervals, and finally the abdomen was 

 bent in a greater degree and its tip was' pointing forward so as 

 to touch the hind legs. The space between the abdomen and 

 femora was about .5 to 1 mm. Suddenly a brown egg-mass was 

 extruded and deposited on the hind femora. This mass was much 

 condensed. The femora remain together to hold the mass on the 

 dorsal side for 2 or 3 minutes after oviposition was accomplished; 

 then by spreading the legs apart the egg-mass was thrown down 

 on the side of the glass container. The mass gradually expanded, 

 becoming fully distended upon touching the water. Later an- 

 other egg-mass was found that had been dropped on an Elodea 

 leaf by another female kept under similar conditions. The egg 

 clusters collected at the shores of pools and ponds were found 

 resting on the bottom in shallow water, floating below the surface 

 or attached to some aquatic plants, depending on how the female 

 throws the mass from her hind legs. 



Each egg measures about .33 mm. long, and .12 mm. broad. 

 It is more or less cylindrical at the middle and round at both 

 ends. Its colour is pale brown, lighter than the eggs of other 

 species, which I have observed, and hardly changes at all from 

 the time when it is first laid until hatched. It has been estimated 

 that there are about 700 eggs on the average in the whole cluster. 

 The cluster averages 9 mm. in length and 5 mm. in width, slightly 



