GRASSHOPPERS IN RELATION TO PLANT ASSOCIATIONS. 163 



Mixed conditions within the area of a habitat also tend to 

 confuse. This is particularly well shown in open forest. Mela- 

 no plus fasciatus and Chloealtis conspersa, of the species studied, 

 are found in open forest with a number of other grasshoppers, 

 but appear to be the only two for which forest conditions are 

 really necessary. All the others are grassland species, and are 

 present because of the grassland environment of the ground 

 stratum. Grassland species may be found in very small sunlit 

 grassy patches within a closed forest. These sunlit patches are 

 not to be considered as part of the closed forest habitat. Prob- 

 ably very few insects of the ground stratum are really typical of 

 open forest. 



Roadsides and other local modifications are a source of error 

 in assigning animals to a habitat. A collector traveling along the 

 sandy roads through the bracken-blueberry growth of the aspen 

 forest would see large numbers of bare-ground CEdipodince, almost 

 all on the roads. He might never realize that these grass- 

 hoppers are not particularly common in the undisturbed growth, 

 and that they are animals of the roads and not of the bracken- 

 blueberry growth. 



Furthermore, the habitat is not entirely uniform within its 

 area. There are many extremely local environmental differences 

 within the habitat, which influence the animal species as well as 

 the plant species. Thus in scattered parts of the bracken- 

 blueberry growth, occasional patches of lichen-covered surface 

 are found. With these patches is associated the grasshopper 

 Scirtetica marmorata. It does not occur over the entire bracken- 

 blueberry growth, as does Melanoplus angustipennis , for instance. 



Within the habitat there are local differences in the degree of 

 development of the vegetation. This is shown in grassland in the 

 degree of openness of vegetation. Where considerable bare 

 surface is exposed between the plants, bare-soil animals are 

 found. In closed grassland, no animals of this habit occur. 

 Differences of development are shown in the aspen forest. Among 

 scattered trees the bracken-blueberry growth presents an en- 

 vironment essentially that of grassland. In more compact 

 tree growths ground conditions begin to approach those of the 

 forest floor. Only in such situations is the short-winged grass- 

 hopper Melanoplus fasciatus to be found. 



