THE 



NATURE-STUDY REVIEW 



Vol. 15 November, 1919 No. 8 



The Burrowing Spider of the Dunes and its Chief 



Enemy 



Elliot R. Downing 



F*rofessor of Biology, School of Education, Chicago University 



The prevailing storm winds over Lake Michigan come out of 

 the northwest. The consequent surf and the currents pile up 

 the sand in bars along the southeastern shores, then fill in the shal- 

 low lagoons behind them and so extend the sandy beach. These 

 same winds pick up the sand as soon as it is dn,- and earn,' it inland, 

 piling it up in great drifts or dunes. These continue to move, 

 encroaching on fields and forests, filling ponds and streams until 

 new dunes built up nearer the lake protect them from the fiuy 

 of the wind. Fig. i . The movdng dimes then become stationary. 

 This fixation of the dune is helped along by the growth of plants 

 upon it — sand-binding grasses, \'ines, shrubs and trees, whose 

 interlacing roots hold the sand and whose tops check the velocity 

 of the sand-laden air currents. So stretching back from the lake 

 is a region covered with dunes and interdunal valleys, all more 

 or less parallel to each other and to the shore. The dunes farthest 

 inland are well covered with woods, those near the shore are 

 moving hills of sand while between these extremes there are all 

 stages of the process of fixation and forestation. 



This dune country, beginning at the very gates of Chicago and 

 extending around the south end of the Lake and well up the east 

 shore, is a wonderful region. Its plant and animal life is a strange 

 mixture of northern and southern forms. You may pitch your 

 tent in a grove of jack pines with an undergrowi:h of jimiper, 

 bearberry, prince's pine, checkerberry and imagine yoiirself five 

 hundred miles farther north, the vegetation is so characteristc 

 of the higher latitudes. The ruffed grouse and many other north- 

 em birds nest here. There are great sphagnum moors, fringed 

 with tamarack, where grow leatherleaf, pitcher plants, sundew 



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