FURTHER RESEARCHES ON NORTH AMERICAN ACRIDIID^. II 



Certainly, if there is a tendency on the part of the organism to 

 assume a coloration resembling that of the environment apart from 

 natural selection through protection from enemies, then we should 

 expect a variation in color correlated in some way with the character 

 of the light rays in different climates, at high altitudes (cf. alpine 

 flowers), on the seabeach, in grassy fields, or sylvan thickets. 



As y^t, however, I am forced to believe that sufficient data of 

 adequate weight have not been accumulated to provide a satisfactory 

 explanation of this color-variation of the wings and hind tibiae. It is 

 a matter with regard to which evidence should be specially collected 

 by careful field observations, by critical study of closely related forms 

 and of climatic data from different sections of the country, and by 

 experimentation if possible. 



NOTES ON COLORATION AND VARIATION. 



As will be readily understood, the character of the trip forbade 

 the payment of much attention to problems of variation or the acqui- 

 sition of material in sufficient series for statistical study. The sub- 

 joined notes are presented as suggestions for those having opportunity 

 to make observations on this topic in connection with the species 

 involved and as a basis for future work. 



Excellent examples of coloration agreeing with that of the envi- 

 ronmental background are presented by Hypochlora alba and Trimero- 

 tropis saxatilis (pi. i). 



The habitat of the former is upon several species of sage (Artem- 

 isia) pale greenish-white in color, and the locusts inhabiting it, young 

 and old, are of the same tint. The photograph shows the striking 

 contrast with customary hues exhibited by these plants. 



In the latter species specimens from the same station vary widely 

 from light to dark in agreement with the hues of the lichened rock- 

 surfaces frequented. Variations of ground-color also occur geographi- 

 cally, examples from the Wichita Mountains exhibiting a flesh-color 

 like that of the ruddy, weather-beaten granite on which they live. It 

 seems highly probable that this relatively sluggish, unwary species 

 (see p. 40) has escaped destruction only by reason of its highly devel- 

 oped protective coloration. Existing, as it now does, only in isolated 

 colonies, in habitats of highly special character, which continually di- 

 minish in area through various physical and organic agencies, it is not 

 unlikely that in the comparatively early future it will become extinct. 



Noticeable color-variations, as yet unexplained, are also presented 

 by the specimens of Melanoplus fasciatus and M. bivittatus femoratus 

 (see p. 47) secured in Alabama, as compared with northern examples. 



