122 



In return the ants secure honeydew and wax from the lice. A closely 

 related aphid, Schizoneura corni Fabr. lives from "September until 

 June on the dogwood (Comas) , and from June until September on the 

 roots of certain grasses" (Forbes, 1. c, p. 89). This insect, upon the 

 original prairie, was probably an inhabitant of the forest margin, or 

 lived near moist places where dogwoods abounded. (This point should 

 be determined at some favorable locality. ) In such a complex, inter- 

 woven community as that of the prairie it is immaterial where one 

 takes up the thread of relations, for if followed carefully without 

 interruption it will lead one about, from one animal to another suc- 

 cessively, until the intimate life of every animal and plant in the com- 

 munity has been reached, and influenced to some extent. Thus the 

 animals living in the soil, at the surface, and among the vegetation are 

 bound together, not only by their changes of habitats, as when a sub- 

 terranean maggot matures and becomes a flower fly, but also by their 

 movements, as when an active wasp or grasshopper burrows in the 

 soil, so that there is a complex interpenetration of relations w T hich ex- 

 tends to all depths, to all horizontal relations, and binds together the 

 entire social community. 



In this discussion only the invertebrates have been considered, but 

 this phase of the subject should not be concluded without emphasiz- 

 ing the fact that all the organisms of a region form a single biotic com- 

 munity, each member of which is related to all the others and to the 

 physical environment. 



IV. The Forest Associations 



1. Introduction 



In a study of forest animals their relation to the physical and vege- 

 tational environment must be kept constantly in mind, in order that 

 their progressive changes may be clearly understood. If the woodland 

 animals and associations are considered broadly, it is possible to study 

 the progressive transformation of the habitats and associations by 

 agencies which erode the land and thus develop the drainage, and to 

 combine with this a study of the successive changes in the vegetation 

 (including vegetable products). In the Charleston region this trans- 

 formation includes the progressive invasion of the prairie by the for- 

 est. From this standpoint it is also possible to arrange the forest as- 

 sociations in a genetic series. 



There is little doubt that this entire region was once treeless or 

 prairie, that in time the forest invaded it, mainly or almost exclusively 

 along the streams. Even at the time of settlement the forests had not 

 spread far from the larger streams ; but by normal forest extension and 



