248 THE CANADIAN ENTOMOLOGIST 



nymphs of eight species were taken and imagos reared, three of 

 which are new species and the nymphs of the other five have not 

 previously been described. The Heptagenia nymphs were the 

 dominant forms in the swift waters and along the exposed shore. 

 Their bodies are very much flattened, legs spreading, femora flat- 

 tened, claws pectinated, gills placed dorsally in an overlapping 

 series, and eyes on dorsal surface of head, and so are adapted to a 

 life in the swiftest water. They are able to cling very tightly, for 

 when they are lifted from a stone, quite a resistance can be felt. 

 The clinging habit is very strong, for if a number are placed in a 

 vessel of water without anything else to cling to, they begin clinging 

 to each other and are sooii all in a mass. They are quite active and 

 are able to scurry over the surface of a stone, even going sideways 

 and backwards. Their food consists of the various algal forms on 

 the stones to which they cling. 



A Heptagenia probably completes its life cycle in a year. It 

 spends all its life in the water except for four or five days as subi- 

 mago and imago. The egg hatches in about 40 days. This calcu- 

 lation is based upon the fact that about two months after the ap- 

 pearance of the imagos of H. iripimctata the small nymphs of the 

 next generation were found, and this is the time required for the 

 eggs of Hexagenia bilineata. The nym.phs moult about once every 

 two weeks, and as the time of emergence approaches, they probably 

 migrate into quieter water. I have not observed the emergence of 

 a Heptagenia subimago in the oi3en, but in the laboratory the 

 nymphs would crawl up the sticks placed in the jars for the purpose 

 and transform just above the water lc\-el. The subimago stage 

 usually lasts a day, but occasionally only a few hours and in the 

 early part of the season it frequently lasted three or four days. 

 Temperature and humidity seemed to be important factors. The 

 imagos commenced their flight shortly after sundown along the lake 

 shore, dancing in their rhythmic up and down manner at a height 

 of from 12 to 20 feet. The females deposited their eggs by flying 

 over the surface of the water and brushing ofT the eggs into the 

 water as they appeared from the openings of the oviducts. Of the 

 eight species the first to appear was H. tripunctata about June 1, 

 and the last, H. liiridipennis, September 2. 



