VICTOR E. SHELFORD. 



Cercopidae (bug) Clastoplera obtusa Say. 



Tettiginidse (leaf hop) .Gypona octolineala Fitch. 



Leaf hopper Jassus obliturus Say. 



Ichneumonidae Thalessa atrata Fabr. 



Lace wing Crysopa rufialbris 



Lace bug Gargaphia tilice Walsh. 



Ichneumonidae Trogus vulpinus Cb. 



Pentatomidae Banasa calva Say. 



Lampyrid beetle Podabrus basilaris Say. 



Lycosidae Wala mitrata Hentz. 



Theridiidae Notionella inter pres Cam. 



Lampyridae Telephorus tubercolatus Lee. 



Harvestman Qligolophus pictus Wood 



IV. DISCUSSION OF DATA. 



An examination of Table I. and the lists of ground and sub- 

 terranean animals, shows that we have on and under the ground 

 a change in species as we pass from the youngest to the oldest 

 stage of forest development. We note also, where data permit 

 estimation of relative abundance, that as we pass from the 

 youngest to the oldest stage, a species is first few in num- 

 bers, then common and later decreasing again. Examination of 

 Table II. and the lists of animals inhabiting vegetation, shows 

 the same phenomenon though the delimitation appears somewhat 

 sharper, possibly because these animals are related to plants and 

 the differences in physical conditions are accompanied by quite 

 different plants. 



We note that in general, with the change of conditions accom- 

 panying the development of forest upon sterile sand or other 

 mineral soil there is also an almost complete change of animal 

 species. This change is comparable to that associated with the 

 development of a stream (Shelf ord, 'n 1 ) and the filling of a pond 

 (Shelford, 'n 2 and 'n 4 ). This change in mores, if viewed at 

 the oldest point in the environmental series, is ecological succes- 

 sion. For example at station $A where beech forest occurs on 

 sand dunes the cottonwood community has probably been suc- 

 ceeded by the pine community; the pine community by the black 

 oak community; the black oak community by the red oak com- 

 munity which has given way to the present beech community. 



