224 A NATURALIST IN THE GREAT LAKES REGION 



and fallen logs. Harvest spiders or daddy longlegs are abun- 

 dant. Among butterflies the wood nymph and wood satyr are 

 conspicuous by their numbers. The forked-tail and round- 

 winged katydids are prevalent (Fig. 322). 



The ground stratum is thickly populated. The most con- 

 spicuous denizen is perhaps the green tiger beetle, and Shelford 

 names the oak-hickory association, on its animal side, the green 

 tiger-beetle association. This brilliant tiger is only one of several 

 predatory ground beetles common on the forest floor. They 

 are about the same as found in the wood frog association. . The 

 commonest inhabitants of the leaf litter are the myriopods, of 

 which various species of "thousand legs" (millipedes) of the 

 genus Polydesmus and "hundred legs" (centipedes) of the genus 

 Lithobius are most prevalent. Thirty or forty to the square 

 yard may often be found when the leaf litter is carefully looked 

 over. They are an important factor in the transformation of 

 the dead leaves to leaf mold. Occasionally one finds the other 

 myriopods common in the wood frog association in the litter, 

 but they are more often under loose bark on old logs; they are 

 not as common as in the beech-maple forest. The same thing 

 may be said of the slugs and snails. The camel cricket (Fig. 307) 

 and the short-winged locust are fairly abundant. The nymphs 

 of cicadas are common, discovered on their way from the soil 

 stratum, where they live, to the trees where they emerge as 

 adults. In dry seasons the nymphs protect themselves from 

 excessive evaporation by building a closed clay chimney up 

 through the leaf mold, rising sometimes an inch or two above 

 the surface. In this they lie until they are ready to accomplish 

 their transformation on the nearby tree trunk. 



There is a constantly changing association in the trunks of 

 the trees, beginning with the standing trunk still in its prime, 

 continuing through the dead standing timber, the fallen log, in 

 its various stages of decay. The rustic borer (Fig. 308) works 

 in the wood of the hickory, oak, and beech trunk even when 

 the tree is robust. The elm borer (Fig. 309) begins work on 



