27 



Acknowledgments 



My grateful acknowledgments are due to the considerable num- 

 ber of assistants who made the collections upon which this study is 

 based. Those to whom I am indebted on this account are James A. 

 West, John J. Davis, George E. Sanders, Wesley P. Flint, Horace F. 

 Hudson, Lindley M. Smith, Alexandre A. Girault, David K. Mc- 

 Millan, Charles A. Hart, and George B. Howard. To Dr. Wm. A. 

 Nason, of Algonquin, McHenry county, I am under obligations for 

 twenty-three collections (1280 specimens) obtained at lights in 1907. 

 I am also particularly obliged to John J. Davis, of the U. S. Bureau 

 of Entomology, for data of collections made in northern Illinois in 

 1914, by means of which I have been enabled to distinguish with 

 certainty the species of May-beetles which were chiefly concerned in a 

 general and serious injury to farm crops by white-grubs in that part 

 of the state in 1912. The determination to species of the large mass 

 of materials brought together was almost wholly the work of another 

 group of assistants, viz. : J. Douglas Hood, James Zetek, Harry C. 

 Severin, and Robert D. Glasgow, and of John A. Grossbeck, of New 

 Jersey, assistant at the time to Prof. John B. Smith, of Rutgers Col- 

 lege. 



Discussion of the Species 



In the following summaries of my data concerning our Illinois 

 May-beetles, I have taken the species up in the order of the numbers 

 collected, the most abundant species first, and have given for each 

 such information as I have concerning their numbers in different years 

 in each of the three main divisions of the state, the places from which 

 the principal collections were made, the periods of their occurrence 

 in the beetle stage, and the plants on which they were taken, with the 

 numbers or ratios from each kind of plant. 



Pliyllopliaga Mrticula Knoch 



Hirticala, aKho nearly wanting in our northern Illinois collec- 

 tions,* is much the most abundant May-beetle in the state, comprising 

 nearly 38 percent of all our specimens. Only 81 of our 43,439 speci- 

 mens of the species came from northern Illinois, and this is only about 

 half of 1 percent of all our May-beetles from that section of the state. 

 In central Illinois, on the other hand, nearly 52 percent of our col- 

 lections, and in southern Illinois about 14 percent, were of this species. 

 In central Illinois, indeed, we found it nearly three times as numerous 



* Among 4,794 May-beetles obtained by J. J. Davis at Galena, in northwestern 

 Illinois, May 28 and 31, 1914, were 758 specimens of hirtieula. It is possible that 

 this central and southern species extends farther north along the Mississippi than 

 elsewhere, a supposition consistent with what is said on another page concerning 

 the extension of southern species into central Illinois along the watercourses. 



