PAPERS ON BIOLOGY AND AGRICULTURE 171 



SEASONAL CHANGES IN THE INSECT POPULA- 

 TION OF AN ILLINOIS FOREST 



(Abstract) 



A. 0. Wkesb, James Millikin University 



The observations on which this paper is based were 

 made in a tract of woodland some sixty acres in extent, 

 located about five miles from the main campus of the 

 University of Illinois, at Urbana, known as the Univer- 

 sity Woods. The higher parts of the area are well wood- 

 ed, the trees being almost entirely maple (Acer saccha- 

 rum ) , while a mixed stand, composed chiefly of maple and 

 elm (Ulmus americana), occupies the lower parts. In the 

 more open situations there is a considerable growth of 

 underbrush, largely Benzion and Asimuia. This area is 

 one of the very few remaining bits of the woodland 

 originally extending into the prairie of Central Illinois 

 along the Vermillion River and its tributaries, and has 

 of course undergone considerable modification accom- 

 panying the development of adjacent lands for agricul- 

 tural purposes. 



For a period of one year beginning July 1, 1921, meteor- 

 ological observations on the succession and stratifica- 

 tion of temperature, humidity, and the evaporating 

 power of the air were taken, and an attempt was made 

 to correlate with the data thus obtained the variations 

 in the animal population of the area studied. 



An attempt was made throughout the period of study 

 to obtain collections, or rather samples, of the animal 

 population as nearly equivalent as possible and in a man- 

 ner at least roughly quantitative. All collections were 

 made near the stations chosen for meteorological obser- 

 vation, and collections from the different strata generally 

 were made on the same day. In the table and the text all 

 collections are dated according to the last day of the 

 week in which they were made, reckoning from Monday 

 to Monday. This day was chosen for convenience because 

 the theromograph and hygrograph sheets were arranged 

 to be changed at this time. 



Because of the difficulties attendant upon quantitative 

 collection from the tree stratum no systematic samples 



