An associational study of Illinois sand prairie . irie forms, which are dominant, will be discussed first. The prairie forms include not only the phytophilous species, butthose geophilous forms v/hich feed upon the plants. The grasshoppersof the subfamilies Oedipodinae and Acridiinae are characteristic geo-philous plant-feeders. These grasshoppers, with the phytophilousTryxalinae, are foremost among the dominant insects of the bunch-grass: they form, the principal food supply for mostjof the predaceousspecies of the association. In descending order of importance, thetypical bunch-grass Orthopt
An associational study of Illinois sand prairie . irie forms, which are dominant, will be discussed first. The prairie forms include not only the phytophilous species, butthose geophilous forms v/hich feed upon the plants. The grasshoppersof the subfamilies Oedipodinae and Acridiinae are characteristic geo-philous plant-feeders. These grasshoppers, with the phytophilousTryxalinae, are foremost among the dominant insects of the bunch-grass: they form, the principal food supply for mostjof the predaceousspecies of the association. In descending order of importance, thetypical bunch-grass Orthoptera are: Helanopius angustipennis^pharagemon~^ scudderiHippiscus phoenicopterusFsinidiar~f ene stralisIlermiria bivittataSritettix thomasi:Ielanoplus atlanis Campy1acantha olivaceaSchistocerca alutaceaScudderia texensisL^ermiria neomexicanaAmphitornus bicolorHippiscus TialdemanTiSyrbula admirabilisConocephalus robustusHippiscus rugosus *i Resting normally upon the bare ground - the opposite of 44 The Orthoptera are apparently the most succossfully adapted grass-eating insects. The grassland formation is of primitive type: thegrasshoppers are very old forms of insects and the time has been am-ple for an intimate adaptation of the locusts to grass food. Theabundance of the individuals, the rapid rate of reproduction, theadaptation to adverse v/inter conditions by means of the annual lifecycle, with the inactive stage in the v/inter, the indifference as tofood plant - are characteristics of these dominant forms. They arethe dominant and most abundant grass-eaters, in spite of their lackof specialized habits and adaptations for defense from their enemiesand from, severe physical conditions. Many other insects, though less conspicuous, are also vj-ell adapteto grass food. Numbers of phytophagous Hemiptera are preeminentlygrass-eaters. Among these are many of the Homoptera, particularlythe Aphididae, a number of the Heteroptera, i
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