NORTH AMERICAN ACRIDIID^E. 21 



found) ; by their distribution locally, horizontally, and vertically; 

 and by the equally characteristic habits, haunts, and distribution of 

 macropterous species as inhabitants of the open field, desert, or 

 savanna. 



The advantages of progression by flight dispersal widely and 

 easily effected, often aided by the wind, ease of escape from many 

 enemies, etc., and the superiority of this mode in open lands are 

 evident to all. On the other hand, long wings and locomotion by 

 flight are disadvantageous amid dense underbrush, where a leaping 

 mode of progression has decided advantages. Organs unused or 

 disadvantageous tend to dwindle and disappear ; hence the loss 

 of wings. 



If the members of a group of locusts, be it genus or subfamily, 

 differ widely in habits as regards these two kinds of environment 

 campestral and sylvan we find a corresponding difference in wing 

 length, as witness the genus Melanoplus, the group Melanopli, the 

 subfamily Acridiinse. On the other hand, if uniformity of habits 

 characterizes a group, similarity of structure accompanies it, as 

 witness the Oedipodinae, a subfamily characteristic of open, more 

 or less arid surroundings, inhabiting barren fields and washes, the 

 drifting dunes of the seashore, or bare crags of mountain summits, 

 shy and wary of approach, seeking safety in flight, and with few 

 exceptions equipped with large and powerful wings. 



BRACHYPTERISM IN OTHER ORTHOPTERA. 



Among other Orthoptera apterous species are numerous both 

 in saltatorial and non-saltatorial families. On examination we find 

 that genera and species inhabiting trees and shrubs {Scudderia, 

 Microcentrum, Cyrtophyllus , Oecanthus, etc.) and open grassy lands 

 (Conocephalus), are prevailingly long-winged, while those inhab- 

 iting either undergrowth (Xiphidhim in part, Odontoxiphidiuni) , 

 crevices and caves (Ceuthophili, Decticinse, many Blattidse, and 

 Gryllidae), or burrows, either of other species or of their own make 

 {Cry ptoce reus, Myrmecophila, mole-crickets in part), are very likely to 

 be apterous or brachypterous, an evident adaptation in structure to 

 habits directly parallel with that of brachypterous locusts (cf. also 

 ants, termites). 



On close analysis it is found that Orthoptera frequenting habi- 

 tats involving- passage over open spaces of considerable extent, such as 

 fields, between trees in forests, and bushes or thickets in deserts, 

 are usually long-winged, flying species ; and others dwelling in an 

 environment of more or less dense, intricate, interlacing vegetal growth, 



