IO FURTHER RESEARCHES ON NORTH AMERICAN ACRIDIID^. 



proximity to it. There can be no doubt in the mind of one who has 

 watched these actions repeated over and over again, of the value of 

 these colors as a means of signaling, of attracting attention, and 

 thereby effecting or maintaining communication between the sexes or 

 the individuals of a community. 



The wing-colors are also frequently displayed during courtship, 

 while the insect is at rest upon the ground or a suitable perch, and 

 even when attacked by enemies. Such is the case in Dictyophorus and 

 Brachystola. 



The colors of the hind tibiae and inner sides of the hind femora, 

 though often bright, are too limited in extent of surface to be of use 

 as a signal during flight. They are entirely hidden when the insect 

 is at rest, but come into view while it is walking and during the stridu- 

 latory movements of the hind legs which most Acridiidae practice in 

 mating-time. These conspicuous non -sympathetic colors, displayed 

 only at such times, thus seem to possess a direct sexual significance. 



The wing and tibial colors differ much, not only specifically, but 

 also individually in the same species, frequently varying, on the tibiae, 

 from clear yellow to red, sometimes deeply infuscated, or from red 

 through yellow and greenish to deep blue, on the wings from pinkish 

 red through orange to yellow and yellowish- white. 



Bruner (Science, xxi, 133) noted an apparent relation between 

 the coloration of the wings and the degree of humidity of the climate. 

 Morse (Psyche, viu, 7) suggested that temperature should also be 

 considered in this connection. Hart in a recent paper (Bull. 111. State 

 Lab. Nat. Hist., vn, art. vn, pp. 214 et seq.) has collected data indi- 

 cating a similar relation of the tibial colors to humidity. As stated 

 by Bruner and Hart, a blue coloration of wings and hind tibiae seems 

 to be associated with a certain degree of aridity of climate, a red 

 coloration with humidity. 



There is reason to think, however, that several factors are con- 

 cerned in this variation of color. Pigmental in character, originating 

 in the life-processes of the body, these colors are undoubtedly sensi- 

 tive to whatever affects the metabolism of the organism, as well as to 

 external agencies. Moisture and temperature, it is possible, play the 

 chief part as factors in this color-variation, but it is quite likely that 

 altitude or atmospheric pressure, character of food, and quality of 

 light are concerned in these phenomena, with reference to the Acri- 

 diidae at least, despite the negative results noted by Tower in reference 

 to L,eptinotarsa, a genus of beetles (Carnegie Institution of Wash- 

 ington Publication No. 48). 



