132 



"Now, a clearing made in the midst of a dense forest forms a natural 

 hothouse, the soil receiving much more warmth on such places than in 

 the shadv woods. We should thus not wonder to see the Cicada ap- 

 pear earlier on such cleared spaces than in the woods." There is there- 

 fore reason to expect the season to be more advanced in glades than 

 in the surrounding woods. 



The peculiar fossorial fore legs of the cicada nymphs are marked 

 structural features associated with the subterranean habitat. Very 

 naturally, too, cleaning reactions are correlated with such a burrower, 

 whose legs become begrimed with the soil. 



Near the surface of the soil the variety of animal life is greatly in- 

 creased. Not only forms which inhabit the soil regularly are present, 

 but many live here for short periods as adults or during some imma- 

 ture stage. It is not possible to draw a sharp line between the soil 

 community, the humus layer community, and the community of the 

 decayed and solid wood for these reasons : the slightly decomposed 

 organic debris on the surface is progressively renewed by leaves, 

 stems, branches, and animal remains, and is transformed below into 

 the humus layer; this also grades upward by all degrees, through 

 decaying wood into solid wood, and on to the living trees. The acid- 

 ity of leaves during the early stages of decay and their alkalinity at 

 an advanced stage is a fact of great importance, as has been shown 

 by Coville ('14). This suggests the paucity or absence of animals 

 in dense matted layers of decaying leaves. 



In considering the animals that live on or near the surface of 

 the soil in Bates woods, certain species seem more characteristic of 

 rather bare mineral soils, others are more representative of open 

 oak-hickory woods, and still others are representative of much 

 humus. The acridiid locusts found in these woods, such as CJilocaltis 

 conspersa and Melanoplus mnplectcns, are woodland rather than 

 prairie in their haunts, and are commonly found near the bare soil and 

 oviposit in it. Here live the woodland cricket ApitJius, the tiger-beetle 

 Ciciiidcla unipunctata, the scavenger Geotrupes splendidus, the mutillid 

 ant SpJiccrophtJialnia, the wasp Psammochares ccthiops and Lycosa; 

 and Ammophila abhreviata buries its eggs here in the soil. 



Among the loose litter harvest spiders (Liolmnuin) were found 

 running about, although they are not confined to these conditions, for, 

 like Calosoma scrutator, they climb trees. The crickets Nemobius 

 found here seem to avoid bare soil. The larva of the beetle Mcra- 

 cantha contracta was found among decaying leaves. 



The animals living in the humus layer of the soil, and in the much 

 advanced stages of decayed wood, are not wholly identical, because in 

 the humus layer roots of living plants and fungi are so often available 



