would be of interest to have figures from the two lakes over com- 

 parable periods of time, but it is obvious that the density of 

 population is much greater in Lake Erie. 



In their brief study of Lake Michigan, Stimpson (1870) 

 and Hoy (1872) found no mayfly larvae. Smith (I87I and I87I4) re- 

 ported only a single specimen from the bottom of Lake Superior, and 

 noted the relative scarcity of cast skins as compared with the lower 

 lakes, Nicholson (1872) found the mayfly larvae rare and confined to 

 shallow water in Lake Ontario, In a small group of samples taken in 

 the same lake in 1922, Adamstone (I92U) found no mayflies. Clemens 

 (1915) made a study of the mayflies of a small area in Georgian Bay, 

 Lake Huron, but gave no data on their abundance relative to other 

 groups. 



In Lake Nipigon, according to Adamstone (192U), the 

 Ephemerida were less abundant than five other groups of animals, 

 Hexagenia was the most abundant mayfly and it reached its greatest 

 concentration (3li per square meter) where the water was less than 

 two meters deep. Muttkowski (I9I8), in his study of the littoral 

 bottom fauna in Lake Mendota, found the mayflies less abundant than 

 the Trichoptera and Chironomidae, and certain groups other than 

 insects. Hexagenia was not recorded for this lake. Baker (I918), 

 working in Lower South Bay, Oneida Lake, in July, found the mayfly 

 larvae rather rare at that time, but enormous flights of adults had 

 been reported for June. Baker stated that Hexagenia nymphs descended 

 to a depth of about 15 feet ([i,5 meters). Three of the Finger Lakes 

 studied by Birge and Juday (1921) had few if any Ephemerida at the 

 depths investigated, although the depths were greater than mayflies 

 usually select, Juday (1922) reported no mayflies in five samples taken 

 in the deeper water (20 meters or more) of Lake George. Ephemerida 

 made up only a small part of the bottom fauna of Green Lake, Wisconsin, 

 even in the littoral zone, where they were found in the largest numbers 

 (Juday, I92U), According to Scott, Hile, and Spieth (1928), mayflies in 

 the littoral zone of Lake tVav;asee, Indiana, were rather abundant, but 

 less so than Amphipoda and Chironomus. Rawson (1930) found the 

 Chironomidat* by far the most abundant group in Lake Simcoe, with the 

 Ephemerida fifth in order of abundance. The mayflies as a group were 

 most abundant where the water was less than five meters deep, but 

 Hexagenia was most abundant at 1$ meters. EggleTon (1931, page 2^9) 

 found only occasional Ephemerida in his study of Douglas Lake and 

 Third Sister Lake, Michigan, and Kirkville Green Lake, New York. 



265 



