ECOLOGICAL SURVEYS 17 



valley sides. Many insects visit flowers in one 

 habitat but breed in another. In this sense, therefore 

 a study carried out on the animal community of a 

 single major habitat creates for working purposes an 

 arbitrary boundary which does not exist in nature. 

 To a certain extent, but a much lesser one, the same 

 is true of plants, when seed dispersal is taken into 

 consideration. 



While realizing that the usual animal community 

 surveyed is partly an artificial segment of a larger 

 animal world selected for intensive study, we may 

 next enquire how many species of animals live together 

 in such a community. This information can be 

 obtained fairly easily from the results of surveys 

 already mentioned. Only it has to be remembered 

 that these are seldom quite complete, and that they 

 work withm certain conventions. Thus soil investi- 

 gators do not usually include the soil protozoa in 

 their lists of animals. These receive separate study. 

 The same is true of ecological surveys of fresh water, 

 where the micro-fauna is tacitly omitted in many 

 instances. In the table given below, the numbers of 

 species collected in various animal communities is 

 listed. The examples have been selected at random 

 except in so far as some surveys do not give the 

 results in a way that can be summarized. No 

 parasites are included. 



The Number of Species in an Animal 

 Community 



No. of 



Habitat Survey Species 



Dry tundra (fjaeldmark), North Suminerhayes and 29 



Spitsbergen, Lat. 79= 50' Elton (1928) 



Arctic heath, West Greenland, Longstaff (1932) 82 



Lat. 64° 40' 



Arctic willow scrub, same area Do. 68 



Arctic drift-line, seashore, same Do. 25 



area 



CaZZwna heath, Oxshott Conamon, Richards (1926) 105 



Surrey, Lat. 51° 20' 



