INTRODUCTION. 
toms of mud, or silt, or sand, and riffles with bottoms of stones 
or gravel. 
Most of the large streams of the region have their origin in 
summit marshes, whose drainage often enters two different water- 
sheds. These marshes have bottoms of deep black muck, and are 
covered with dense growth of vegetation. Alders form almost 
impenetrable tangles and sedges and grasses, and sometimes bog 
moss, sphagnum, grow in thick mats under foot, helping to impede 
the off-flow of water. Through these soft muck bogs the streams 
meander, their waters always shaded by overhanging alder thickets, 
supporting hardly any living vegetation. These upland bogs har- 
bor many forms of animal life that are characteristic of such situ- 
ations, and of the more northern Canadian fauna. 
The largest upland swamps are the McLean Bogs and Michi- 
gan Hollow, whose southern drainage flows into the Susquehanna 
River, and whose northern drainage forms Buttermilk Creek, 
flowing into Cayuga Lake. 
More work for the present paper was done in the McLean 
Bogs than in all other situations together. These bogs are situ- 
ated along, and near, Beaver Creek, an affluent of Fall Creek, 
about fifteen miles from Ithaca. They offer not only typical bog 
conditions, with areas of sphagnum, areas of sedge, and areas of 
alder swamps, but also several cold swamp streams, an open pond, 
and numerous large springs. 
Since the early days of Cornell, when the hills surrounding the 
bogs were covered with an impressive growth of huge hemlock 
trees, till the present time, they have been a favorite collecting 
ground for students in all fields of biology. 
There are also several small lakes in the region. Of these we 
are concerned with but a few. Beebe Lake, a dilation of Fall 
Creek, which serves as a reservoir for Cornell University, is con- 
venient to the Campus, but is not very prolific of insect life. Michi- 
gan Pond, at the northern end of Michigan Swamp, has soft mud 
bottom and a profuse growth of aquatic plants. It is a rich col- 
lecting ground for aquatic insects. Spencer Lake, in the Susque- 
hanna drainage south of Michigan Swamp, is a beautiful little 
lake which offers a great variety of aquatic situations. It is rich 
in caddis-worms, especially the Leptoceride. 
With these various kinds of aquatic situations within con- 
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