The color variations of the grasshopper, Melanoplus bivittatus Say, occurring under similar environmental conditions, are described;The methods of extraction of the pigment are described;The yellow pigment, the presence or absence of which is largely responsible for the occurrence of variation in the adult color type, was identified, by spectroscopic and chemical analyses, as carotin;Carotin was found to be present in a concentration of 0.0436 milligram per gram of body weight in the females; of 0.0436 milligram per gram of body weight in the males (both determinations with the alimentary canal removed); and of 0.266 milligram per gram of tissue in the reproductive organs and surrounding tissue. All determinations were made by comparing the pigment with a 0.2 percent potassium dichromate solution in a Baush and Lomb colorimeter;The procedures followed in the rearing of the grasshoppers, for the purpose of studying the effects of certain environmental factors on their coloration, are described;Experiments were conducted to determine the effects upon the coloration of the nymphs, and the color types of the adults, of the two-lined grasshopper of such factors as temperature, humidity, rearing many per cage as opposed to one per cage, the absence of light, and different-colored lights. The results of the experiments are stated in tables I to VII;The results obtained in the F1 generation form mating typical males and females of each phase are reported in table VIII.