44 



the southern sections. Nitida seems even more distinctly northern, if 

 we may judge from our small collections, entirely from Aurora and 

 Algonquin, and nearly all from hazel thickets in the forest border. 



Northern-Central Species. — Three of our May-beetles, fusca, in- 

 versa, and drakii, altho most abundant northward and virtually ab- 

 sent from southern Illinois, are sufficiently at home in the central 

 district to warrant our grouping them as northern and central species. 

 Fusca, for example, which gave us 28.2 percent of all our northern 

 Illinois May-beetles, yielded also 9.4 percent of those from central 

 Illinois, but virtually none from farther south. The corresponding 

 ratios for inversa were 8.8 percent northern, 12.4 percent central, and 

 none southern ; and for the much less abundant drakii they were l.o 

 percent, .18 of 1 percent and .04 of 1 percent respectively. Otherwise 

 stated, for each 1000 of drakii taken in northern Illinois we might 

 expect, in an equal number of similar collections, 100 from the central 

 part of the state and 2 or 3 from the southern. What physiological 

 or ecological conditions limit the distribution of these species south- 

 ward it is impossible to tell without much more detailed and intensive 

 ecological work than has thus far been attempted by us. We may 

 only note that all three of these species have a diversified food habit, 

 and belong to neither of the great groups of poplar- willow or oak- 

 hickory-persimmon species. 



Central- Southern Species. — Two of our species, hirticula and 

 fervida, common to central and southern Illinois, are nearly wanting 

 to the northern part of the state. Hirticula, a decidedly general 

 feeder with an apparent preference for oak and hickory, has a much 

 larger representation in southern Illinois than in central, making 

 more than half our total collections in the former and less than 15 

 percent in the latter. Its numbers in northern Illinois we found quite 

 insignificant; altho 11.6 percent of the Galena May-beetles collected 

 by Davis in 1914 were of this species. Fervida, on the other hand, 

 was much more distinctively southern, giving us 3.4 percent of our 

 southern Illinois May-beetles and a little over 1 percent of those from 

 central Illinois, with only a single specimen from farther north. It is 

 an oak-hickory-persimmon species. 



Southern Illinois Species. — The eleven properly southern Illi- 

 nois May-beetles are all species of the southern states which find their 

 northern limit in the southern part of Illinois. They are a fairly 

 uniform group in respect to their food, as is shown by the following 

 list of their principal food-plants. 



Bipartita: willow, hickory, oak. 



Corrosa: persimmon, oak, hickory. 



Crenulata : persimmon, willow, hickory. 



Delata : oak, hickory. 



Forbesi: cherry, peach, apple. 



Forsteri: oak, hickory, persimmon. 



