GRASSHOPPERS IN RELATION TO PLANT ASSOCIATIONS 159 



areas of dry grassland, of marsh, and of forest. However, while 

 at rest, very few will be found on trees, for example, or in deep 

 shade, or in dense herbaceous vegetation. They will usually be 

 seen in open dry vegetation or on bare soil. If found in other 

 conditions, these will usually be not far distant from such open 

 situations. Stray individuals are not common and are usually 

 found singly. It is not surprising that stray individuals should 

 be more frequent among species which are very abundant in the 

 region, as Camnula pellucida, and among species of the more 

 extensive habitats. The motility of animals is perhaps com- 

 monly overestimated as a factor in width of local distribution. 

 The daily itinerary of an animal is likely to be more circumscribed 

 than is usually thought. In the case of the grasshoppers again, 

 for most species the ordinary mode of progression is walking or 

 crawling, rather than jumping or flying. Usually grasshoppers 

 are noticed only when disturbed, or "flushed." Their behavior, 

 jumping or flying when disturbed, is a special reaction to an 

 approaching object. The ordinary activities are much less fre- 

 quently observed. Birds, our most motile animals, have very 

 definite habitat relations (see Gates, 'n). Though the actual 

 number of observed occurrences of stray individuals in unusual 

 situations may be large, these occurrences are very infrequent 

 and exceptional when compared with occurrences in the normal 

 habitat. 



Differences of Activity in Different Habitats. Various activities 

 of the animal may take place in different strata of one habitat, or 

 in different habitats, separated horizontally. The stratum or 

 habitat of greatest importance to the animal is the one in which 

 the most narrowly limited activity takes place, and this activity 

 is usually concerned with breeding (Shelford, '07, 'n). 1 In the 

 case of the Douglas Lake grasshoppers, eggs are laid just below 

 the surface of the soil, or at least in the ground stratum, and 

 proper conditions for oviposition are among the most important 

 considerations which determine the presence of the particular 

 species in the region, and the important consideration in deter- 

 mining which habitat within the region is most essential to the 



1 On p. 595 (Shelford, 'n) are given references to other authors, in which in- 

 stances of breeding activities as being most narrowly limited are given for birds 

 and for fishes. 



