APPENDIX 



METHODS 



General methods of ecological investigations are treated in various refer- 

 ence works (Abderhalden's Handbuch, 1925-1931; Adams, 1913; Shelford, 

 1913, a; 1929, a), and only a few features of procedure with reference to 

 animals are presented. 



Let us assume a sample catch of all the organisms from 10 square kilo- 

 meters of primeval grassland (or a similar area of sea bottom). The grassland 

 catch would include everything from the bison to the soil bacteria and 

 Protozoa. The community function of these various organisms could not be 

 determined from inspection. Some of them would be relatively large and con- 

 spicuous, others numerous and made noticeable by their numbers and ex- 

 tension over large areas. Quantitative methods are absolutely necessary. 



On the basis of size and abundance, various degrees of influence and domi- 

 nance may be roughly recognized, but the actual community functions still 

 have to be determined by long study, both field and laboratory; but no matter 

 what the results may be, the abundance of any organism is a matter of 

 first importance, though often very difficult to ascertain. 



After all the dominants, subdominants, and influents of various grades 

 have been evaluated as far as is ordinarily practicable in a field investigation, 

 there may remain many small organisms to which no relative value can be 

 assigned. These are small herbs, insects, fungi, bacteria, protozoans, lichens, 

 and various invertebrates. The more abundant of these still have to be called 

 predominant or prevalent among their kind. After evaluation in one locality 

 is completed, organisms have further to be evaluated as to their geographical 

 extent, uniformity of distribution, and stability of mnnbers. This further 

 evaluation is usually accomplished in connection with the recognition of the 

 largest communities of which the local ones are a part. Abundance is always 

 a prime consideration, though ideally the force exerted by the populations 

 is the fact required and sought. 



In terrestrial communities two principal methods are used in dealing with 

 smaller invertebrates. Placing an inverted can over a known area at the time 

 of minimum activity and killing and recovering the organisms (Wolcott, 1918; 

 Shelford, 1929, a; Beall, 1935) is one standard method. The use of the sweep 

 net to secure invertebrates from the vegetation is a general one and has been 

 discussed especially by Zubareva (1930), Gray and Treloar (1933) and Beall 

 (1935). Gray and Treloar selected an alfalfa field because of its uniformity, 

 but their results indicate that the insect population is more heterogeneous 

 than that of a climax vegetation, and this is to be expected because of the 



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