GRASSHOPPERS IN RELATION TO PLANT ASSOCIATIONS. 177 



certain habitats by themselves, so far as grasshoppers are con- 

 cerned, have the most common type of life-history, hibernating 

 in the egg stage and active from early July till frosts, suggests 

 that antagonistic influence is not a factor in determining their 

 life-histories. Such species are Stenobothrus curtipennis in 

 marshy growths, and Melanoplus islandicus in deep forests. 



It appears that the species with least definite habitat-prefer- 

 ences (Melanoplus atlanis, M. femur-rubrum, M. bivittatus) have 

 also least definite life-histories. They mature early, remain 

 active till frosts, and are sometimes two-brooded. Their wide 

 distribution in time is probably due to the same cause as their 

 wide distribution in space, namely, their lack of responsiveness 

 to slight differences in environmental conditions. 



V. SUMMARY. 



Distribution of grasshopper species within the region studied 

 bears evident relation to the plant associations. The plant 

 association is the index to environmental conditions, and its 

 extent marks the area of the habitat. In studies of local dis- 

 tribution within a region, all the plant associations, including 

 local and ruderal associations, should be considered, since other- 

 wise certain habitat relations may be overlooked. 



As an environmental complex, the plant association is usually 

 more inclusive than the total of conditions required by a particu- 

 lar species, particularly if it is climatic or extensive. Associations 

 may be similar as environments for grasshopper species if they 

 agree merely in including physical and vegetational conditions 

 critical to those species. Grasshoppers select habitats or asso- 

 ciations in which favorable conditions are to be found, irrespec- 

 tive of past history, extensiveness, geographic or successional 

 relationships of the vegetation. There is very seldom any direct 

 relation between grasshopper species and species composition 

 of the plant associations, as few grasshoppers are selective 

 feeders. 



Most of the grasshopper species are of the ground stratum, and 

 soil conditions are essential. These grasshoppers are typical of 

 open herbaceous associations, characteristic in initial stages of 

 vegetational development in dry ground. Species of open forest 



