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 Fic. 211.—The lacebugs common on the oak 
and wild cherry in the dune region (Corythuca 
to which the sand is shifted arcuata) (from Washburn after Comstock): 
by the wind. Ontheparallel  ¢, adult; }, young. 
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. 
V. Mesopuytic 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.—tIn 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 
