RED-OAK ASSOCIATION 



233 



d) Tree stratum. — The black oak (137) is attacked by a large, light- 

 green larva which has a narrow yellow stripe down its back (Nadata 

 gibbosa). It is also attacked by several slug caterpillars which we have 

 been unable to identify. The beautiful prominent larva with a saddle 

 of red is occasionally taken. Commonly feeding on the juices of 

 the leaves are several species of leaf-hopper (Typhlocyba querci var. 

 bifasciata), the common grapevine leaf-hopper, and the white black- 

 marked leaf-hopper which occurs also on the hickory. The oak tree- 

 hopper (Telemona querci) (Fig. 212) is a common leaf-sucker. Squirrels 

 are probably occasional visitors as they come to feed upon acorns. The 

 acorns are also often attacked 

 by weevils. 



In such a set of graded 

 forest stages as we are dis- 

 cussing it is possible to note 

 many stages. The stage 

 which we have just de- 

 scribed passes more or less 

 rapidly into the next, the 

 rate of change depending 

 upon the height above 

 ground water and the degree 

 to which the sand is shifted 

 by the wind. On the parallel 

 ridges, the next and perhaps 



most notable forest stage contains white oak and red oak and is found 

 in places on the Tolleston, Calumet, and Glenwood beaches. The 

 ecological age of the forest is determined by the height above ground 

 water. Ridge 93, inside the Tolleston Beach, is low and forest has 

 progressed as far as on the older beaches. 



Fig. 2ii. — The lacebugs common on the oak 

 and wild cherry in the dune region (Corythuca 

 arena ta) (from Washburn after Comstock): 

 a, adult; b, young. 



V. Mesophytic Forest Formation (115, 170) 



I. HYALIODES OR BLACK OAK-RED OAK ASSOCIATION 



(Station 63, also near stations 27 and 65; Tables L, LIII, LVI, LIX) (115) 



This is represented at several points. 



a) Subterranean-ground stratum. — In this stratum the woodchuck 

 or groundhog is common (142). Earthworms have begun to appear. 

 The root-borer Prionus (155) and several species of ants are common, 

 while the numerous digger-wasps of the earlier stage have largely dis- 

 appeared. The depressions which contain water in spring are typical 



