ECOLOGY OP ISLE ROYALB. 15 



is clearly seen that among these there are several elements of the 

 Balsam, White Spiruce and Birch forest society, which tends to ulti- 

 mately possess the ridge. 



The fauna of the ridge is quite diversified, and there is a general 

 faunal correlation corresponding with these successions of the vegetation. 

 Thus during the Lichen-Heath stage, ants and spiders, certain shells, 

 and grasshoppers are abundant. As the soil becomes thicker or the 

 crevices deepen, a subterranean fauna, consisting of myriapods, earth- 

 worms, etc., develops. As shrubs and trees encroach in patches, the 

 animals frequenting the open tend to perpetuate themselves mainly at 

 the open margins. Prom this condition on, so far as the fauna is con- 

 cerned, it is largely a question of an ''opening" or a forest environment. 

 So long as this habitat remains open, the grasshoppers, ants, spiders, 

 butterflies, flies, and certain Hymenoptera, Hares and Bats are character- 

 istic, and this condition tends to continue as long as the trees are 

 scattered. The Cicada is very characteristic of the Jack Pine stage, 

 and although it occurs elsewhere in young Birches it is not so character- 

 istic as on these hot ridges. With the advent of the Balsam-Birch society, 

 which is slowly encroaching upon the ridges, the forms frequenting the 

 open will disappear, or linger in the open spots where local conditions 

 have retarded the advance of the forest. Only a few birds were seen 

 here, but Hares had been numerous, as was shown by the large amount 

 of excrement, and there was similar evidence of the occurrence of the 

 Lynx. A bat was flushed from under a stone at the edge of the escarp- 

 ment. 



Station I, 6. Tamarack-Spruce Bog. This is a very small bog located 

 ai the base of the north slope of the Jack Pine Eidge (I, 5), and roughly 

 estimated as about 250 by 300 feet in extent. The central part is 

 covered with sphagnum, Cassandra, and a scattered growth of Labrador 

 Tea. Widely scattered throughout the bog occur Tamaracks and Black 

 Spruces, small Birches, Dwarf Cranberry, Cotton Grass and alders. No 

 standing open water was found in this area, nor was the bottom quaking. 

 Bordering the sphagnum zone is one of alders, willows, and a tall grass 

 which merged into a zone of Tamaracks, willows, alders, Cassandra and 

 Balsam:, Fig. 14. Along the western end a narrow strip of water, a 

 few inches deep, was found, which flowed through a ravine across the 

 ridge. Along this outlet the deeper soil and moisture has permitted 

 tl>e development of Balsam, Birch, Small-toothed Aspen, Mt. Maple, 

 Ground Hemlock, Ground Cornel, Large-leaved Aster, and a few Black 

 Ash trees. 



The fauna, like the vegetation, was not studied in detail, but the fol- 

 lowing general relations were observed. In the open central Sphagnum- 

 Cassaudra society were numerous large aiut nests. A Toad was ob- 

 served here; and the following birds: Golden-crowned Kinglet, White- 

 throated Sparrow, Cedar Waxwing, and Black-throated Green War- 

 bler. 



Station I, 7. Light-house Clearing. This was a small clearing which 

 has been made about the Light-house: it connects by a path to the fish- 

 ing camp on Bock Harbor. It covers about half an acre, and Avas origi- 

 nally, in all probability, a Balsam and Spruce forest like the surround- 

 ing forest. A sod covered much of the ground, and there were numerous 



