136 Survey of Soil Fauna of Agricultural Land 



little attention, apart from the valuable work of a small number of 

 investigators. In America something has been done to formulate the 

 principles and methods of animal ecology by Adams, Forbes, Shelford, 

 Vestal and others. In this country almost the only serious attempt at 

 this problem is due to Cameron. The present paper is an endeavour to 

 extend his investigations on soil-insects from grassland to other types 

 of agricultural land. 



It is by no means easy to find the distribution in space of the associ- 

 ation if the definition of Forbes is accepted (1907). 



Cameron has suggested (1916) that a difference in the fauna of two 

 areas possessing different soil-types and vegetative coverings is due to 

 different environmental conditions. 



The fauna in an area may exist, however, without any ecological 

 connection between the different species. They may not form an asso- 

 ciation. If the fauna in two areas come together without any ecological 

 relationship {i.e. by chance) it is not possible to state in what degree 

 environmental conditions operate since this chance occurrence may take 

 place under very diverse environmental conditions. Even if an associ- 

 ation occurs it may be largely composed of areas of associated species 

 without any ecological connections. There may be also environmental 

 differences within the association allowing of the presence of a different 

 type of fauna. At the same time the species most frequently found seem 

 to occur irrespective of soil-type and the majority of species, being 

 adapted to general feeding, are not restricted to particular plant species 

 or vegetative covering. 



If the definition of the association is followed it seems that it 

 operates over broad tracts of country comparable with climatic regions, 

 thus, to the isolated worker to whom the investigation of more than a 

 strictly limited area is impossible, the association has a theoretical 

 rather than a practical value, and it therefore becomes necessary to 

 find some smaller or more practical basis for his research methods. 



An attempt therefore has been made in this investigation to stan- 

 dardise the soil-types as far as possible. If instead of taking an area 

 with a varied number of soil-materials, one soil-type is used, more 

 accurate information can be obtained as to the physical condition of 

 the soil, water-content and aeration. In this way the environmental 

 conditions may be expressed to some extent in terms of the soil-type. 

 It is felt that if the results from a number of individual surveys are linked 

 together to cover large areas the solution to the whole problem may be 

 found. 



