438 Wisconsin Academy of Sciences, Arts, and Letters. 
so scattered early in the season, are extremely abundant and 
practically ubiquitous. The same is true of leeches, Hydrach- 
nida, and smaller Bryozoa. Among insects the shoreward mi¬ 
gration of the larvae of Ephemera varia is of interest; that is, 
the younger larvae have lived in the sands of the plant zone dur¬ 
ing early summ^er, and the older larvae now migrate to their 
habitat in the rachion and stony shores. Among Chironomids 
Chironomus digitatus, lobiferus, fulviventris, viridis, palliatus, 
and others reach their larval maxima at this period. 
Autumnal Succession—Period of Diminution. —The ascend¬ 
ancy lasts till early September, when there is a falling-off 
throughout the lake community. While the falling temperature 
may effect this to some extent,— for instance, in the case of Core- 
thra,—it is probable that the molar agents in the form of equi¬ 
noctial storms are the most important factors. Lake circula¬ 
tion is quickened by the storms and the falling temperature, and 
the return of oxygen to the aphytal area stimulates the anaerobes 
and adjoining bottom fauna to renewed activity. 
Sialis at once migrates downward to the newly accessible 
feeding-ground. The return of the oxygen stimulates Chirono¬ 
mus tentans and Protenthes choreus to pupation and there 
follows an autumnal flight of these species. Some of the Tany- 
tarsus species of the dysphytal area are also stimulated to trans¬ 
formation, but they do not form any conspicuous element such 
as their relatives. 
Some of the autumn storms are of great violence and the havoc 
wrought by them among the plant and animal life of the lake 
is immense. Potamogeton, Najas, Vallisneria,—practically the 
entire upright vegetation is broken loose; much of it is cast 
ashore, portions are set adrift on the lake and later on sink to 
the bottom. 
Much of the faunal life of this vegetation is east on shore or 
battered to death in the surf. In November, 1914, after one 
of these storms, there was a great shore drift in Sunset Bay, 
between Picnic and Sunset Points. This drift was some 30 
meters long, about 2 meters wide and 15 cm. deep, and was com¬ 
posed almost entirely of dead Leptocellae in their cases. A 
second drift, even greater in extent, lay in the water. According 
to an estimate, there were at least flve million specimens in this 
drift. And this was only for a very small portion of the lake 
off Sunset Bay. 
