Article I. — An Associational Study of Illinois Sand Prairie. 

 Bv Arthur G. Vestal, A.M. 



Introduction 



Three reports on the biology of the sand areas of Illinois have ap- 

 peared in earlier numbers of this Bulletin. The report of Hart and 

 Gleason ('07) is a discussion of the plants and animals in the par- 

 ticular region in which the present studies were made; that oc 

 Gleason ('10) gives an account of the plant associations of the inland 

 sand areas of the state; and that of Gates ('12) discusses the plant 

 associations of the sand area of the Lake Michigan shore near the 

 northern boundary of Illinois. The present study is restricted to the 

 grassland associations of sand in the Illinois River valley, and the 

 emphasis is placed upon the animals of the region. The unit of study 

 is here the association, or community of organisms: the social aggre- 

 gate of plants and animals, which, living in a common environment, 

 come into various relations one with another. In the sand prairie of 

 the river valley several types of areas may be distinguished, each 

 characterized by a definite set of physical conditions, by a particular 

 association of plants, and by a particular assemblage of animals. In 

 this report the plant and animal assemblages are considered together, 

 and inquiry is made into the relations which obtain between them, and 

 between them and the physical environment. 



The field work was done at Havana, Mason county, Illinois, on 

 the Illinois River, during the summer of 19 10, and during short 

 periods in early fall in 1910 and early spring in 1911, — nearly all in 

 an area of almost pure sand east of Havana, locally known as the 

 Devil's Hole, somewhat less than two miles distant from the river. 

 Several excursions were made to the Devil's Neck, a similar but much 

 larger sand area north of Topeka, and to various other points in the 

 valley. More attention was given to the insects than to any other 

 group of animals, this partiality being justified by the fact that thev 

 are the most numerous and the most conspicuous forms in the animal 

 life of the sand prairie. 



Acknowledgments 



The preparation of this report would not have been possible with- 

 out the aid of many persons. Dr. C. C. Adams, under whose direction 

 the work was done, has been of very great assistance in many ways. 



