Hubert ML Morris 153 



As has been mentioned above, the difference in temperature between 

 tbe upper and lower levels of the soil appeared to have little effect on the 

 insects. 



Thus the first three conditions were distinctly unfavourable to deep 

 penetration of the soil by the insects in this case, while the fourth con- 

 dition was found to have little effect on the depth to which insects 

 descended. 



Of the four factors given above, the first, the occurrence of the 

 particular food required by the insect, is largely controlled by the flora 

 of the area, while the second and third, aeration and moisture respectively, 

 are largely controlled by the texture and composition of the soil, which 

 in turn influences the flora. Other factors the influence of which on the 

 insect fauna must be considered are light, wind, rainfall, atmospheric 

 pressure, altitude, exposure and slope. In the present instance these 

 factors do not require to be considered in detail as they would be prac- 

 tically uniform over the district of which the area under observation was 

 selected as being typical. 



11. Discussion of Previous Work. 



It is noticeable that in this investigation many fewer species were 

 met with than were recorded by Cameron (1917) in his investigation in 

 the same district. This difference is largely accounted for by the fact 

 that in the present instance care was taken to select an environment as 

 uniform as possible, in which little invasion by insects not belonging to 

 the area under observation would occur. In the former case the area was 

 of a very composite nature and included a small wood and fields under 

 various crops. In addition, his two pastures were much "rougher" than 

 that now dealt with, containing a much larger proportion of weeds, and 

 patches of long grass. In his earlier work (1913), Cameron also dealt with 

 an area which was not uniform, and included a field which had been 

 artificially levelled and a small orchard, with several decaying logs and 

 vegetable refuse. 



In both the above cases there was a much greater variety of food 

 available, and consequently many more species of insects were present, 

 and there was also considerable variation in the texture of the soil in 

 different parts of the area. 



It is rather remarkable that a greater number of individuals should 

 have been found in this field than in either of the fields in the same dis- 

 trict examined by Cameron, which are marked Lc and N on the map. 



