45 



Fraterna: oak, hickory, persimmon. 

 Micans : persimmon, oak. 

 Praetermissa: oak, willow, apple. 

 Profunda: oak, hickory, persimmon. 

 VeJiemens: food unknown. 



Comparison of the Sections of the State 



The greater diversity of surface and variety of ecological situa- 

 tion shown in southern Illinois, with its level prairies of gray silt 

 loam to the north changing gradually into the broken country of the 

 Ozark hills at the south, bordered on the west by the broad bottom- 

 lands of the Mississippi and on the south by the Ohio, create local 

 conditions whose wide diversities are reflected in the various composi- 

 tion and ratios of their insect inhabitants. Central Illinois, on the 

 other hand, has a much more monotonous topography and a May- 

 beetle population more uniformly distributed. Our May-beetles from 

 Anna in the years 1908 and 1909 were much less like those from 

 Carbondale, only seventeen miles away, than were those of Galesburg 

 like those at Urbana, a hundred and twenty-four miles apart but both 

 in the central Illinois prairie region. The five most abundant species 

 in 1908 were the same at the latter two towns, differing only slightly 

 in the order of their numbers, which amounted, at each place, to 99 

 percent of the May-beetles collected at these points in that year ; while 

 in southern Illinois only two of the five most abundant species at 

 Carbondale and Anna were common to both lists. The first and sec- 

 ond of the Anna list were ninth and tenth of the Carbondale list, the 

 third at Anna was the second at Carbondale ; the fourth was the first, 

 and the fifth was the fourteenth. 



Looking in some detail at the extension of distinctively southern 

 species into central Illinois, we find that it is especially notable at 

 points where central Illinois streams are bordered by broken wood- 

 lands — where, in other words, the ecological conditions approach those 

 of the hill country of the southern part of the state. Danville on the 

 Vermilion, Decatur on the Sangamon, and Havana on the Illinois, are 

 such locations, and here southern species were taken in 1907 and 1908 

 as follows : at Danville, crenulata, forsteri, fraterna, and vehement : 

 at Decatur, crenulata and veJiemens; and at Havana, crenulata, and 

 micans, — five of the eleven mainly southern species at one or more of 

 these central Illinois points. The real boundaries of our areas of dis- 

 tribution are, of course, not the artificial lines separating the con- 

 ventional sections of the state, but they run a highly irregular course, 

 their meanderings guided largely by the location of our streams. 

 The southern species are, however, represented, as a rule, in central 

 and northern Illinois by numbers so small that they can cut no figure 

 in the general mass of the May-beetle population of the central and 



