ANIMAL ECOLOGY OF JOHNSON COUNTY — 25 
to insects, that no attempt will be made to summarize it here.’’ 
The decaying wood habitat demands attention in this connec- 
tion on account of the increase in fallen limbs, twigs, and even 
standing and fallen dead trees. The decay of wood begins as 
soon as moisture and fungi succeed in entering the plant tissue. 
From this point on the animal habitats afforded by the decaying 
wood pass through a regular ecological series. In a fallen log 
decay usually begins in the sap-wood layer just beneath the 
bark. This causes the bark to loosen, providing a home for many 
insects, such as the adults and larvae of wood-eating beetles 
(Pyrochroidae, Tenebrionidae, and certain Elateridae) and ants, 
as well as mollusks and myriapods. Once a foothold is thus 
gained, the activities of the insects and the fungi which become 
established act upon the wood beneath until in a few years or 
many years, depending upon the kind of wood—in oak, many 
years—the whole is reduced to a mass of thoroughly rotten wood 
ready to be worked into the humus. There is, of course, a cor- 
responding change in the kinds of animals which are to. be 
found as the process of decay advances. Among those forms 
encountered in the advanced stages of decaying wood are Cole- 
optera, larvae of Lucanidae, and certain Scarabaeidae, as well as 
numerous adult scavenger beetles. Mollusks, particularly the 
slugs, are common. Such places provide the most favorable 
hibernation refuges for the female bald-faced hornet. 
Oak timber with undergrowth. This formation differs from 
the preceding chiefly in the fact that the undergrowth gives an 
added density to the vegetation. Here we find a further in- 
erease in shade and humidity. The sub-habitats are quite similar 
to those of the pastured oak timber save that there is a quite well 
defined shrub or undergrowth stratum. This stratum consists, 
vegetationally, of many annual flowering plants, ferns to some 
extent, and such woody shrubs as the hazel. The undergrowth 
provides an abundance and wide variety of food plants, which 
therefore make for a corresponding variety of animal forms de- 
pending upon living tissue for their food, a large number of 
individuals being, in this case as in the others, insects. For 
example, the walking-stick, while not limited to this particular 
sub-habitat, is most frequently met among the twigs of the small 
