64 MICHIGAN SURVEY, 1908. 



landeri Ball (80, 163, 164), Amnicola lustrica Pils, (89, 163, 164), and 

 Pisidium sp. (163, 164), and Amphipods were dredged from a depth of 

 1.5 to 2 meters near the mouth of a small stream {Fig. 22) where the 

 bottom was thickly covered with small twigs and other coarse vegetable 

 debris. From the same place the caddice fly larvae were obtained, as 

 mentioned previously. The same fauna was collected in the stream it- 

 self, but only near the mouth, where the water was deep, the cvirrent 

 slow, and the conditions in general much like those of a lake. May flies 

 probably breed in similar places. No larvae were seen, but a few images 

 were collected (No. 178). 



The fauna of the bottom shows a connection through the presence of 

 Pisidium sp. in the last case with that of the small streams in the 

 tamarack swamps and with that of the brooks, like the outlet of Siskowit 

 Lake. The accumulation of vegetable debris and the more restricted 

 amount of water are both approaches toward the conditions in the former 

 places. In Siskowit Lake, where Planorhis campanulatus, Phmorhis 

 hicarinatus ropalensis and Anodonta grandis footiana were associated 

 with Limnaea stagnalis, another transition was shown between the faunas 

 of the inland lakes and the larger lakes as typified by Lake Superior 

 itself. 



b. The Free Fauna of the Water. No species were observed except 

 fishes and leeches. The latter were abundant in Sumner Lake, especially 

 among the water lilies and in the shallow water along the shore. 



c. The Fauna of the Surface. Hardly belonging properly to this 

 groiip were the small shells, Limnaea catascopium Say (220), Physa sp. 

 (220, 221), Valvata sincera nylanderi Ball (220), and Amnicola Unwsa 

 Say (220), found abundantly on the under side of water lily leaves. Their 

 distribution is directly controlled by that of the water lilies, that is, 

 near the shore, and in the larger lakes only in the sheltered bays. Pro- 

 bably a third of the leaves had one or sometimes two shells attached 

 to them. Water stridors, Gerris remigis Say (No. 96), were abundant, 

 usually near shore in the water lily zone, but occasionally out in the 

 open water. Whirligig beetles, Gyrimis minuttis Fabr. (No. 219) were 

 also common, but not abundant on the smaller lakes. In the sheltered 

 bays of Siskowit Lake they collected in immense swarms, keeping mostly 

 near the shore among the water lilies and under overhanging brush. 

 Donacia proxima (Nos. 171, 184) and Donacia cincticornis (Nos. 171, 

 175) were abundant on Sumner Lake, resting on the water lily leaves. 

 When alarmed they would fly a short distance close to the water, making 

 a little trail behind them, and alight on another leaf. 



d. The Free Aerial Fauna. Bragonflies of several species are abun- 

 dant along all of the lakes. They usually keep close inshore or over 

 the water lilies, and fly regularly in patrols around the lake, searching 

 all the time for insects but keeping up a uniform rate of speed. Aeschna 

 sp. was probably the most abundant, and associated with it were 

 Enallagma hageni Walsh and L&ucorhinia proxima Anth. The butterfly 

 Argynnis atlantis Edw. also occurs (No. 169). 



The inland lakes may be regarded as small detached portions of the 

 main lake, cut off from it by the lowering of the level of the latter. 

 Since they are composed of stagnant water with little or no wave action, 

 where organic material may accumulate in quantity, they support a 



