160 CAROTINOIDS AND RELATED PIGMENTS 



or ether, were purified merely by repeated re-solutions and evapora- 

 tions. The amorphous residue finally obtained contained 7.7 per cent 

 nitrogen, and showed a gross composition conforming to the formula 

 C 7 H 5 N0 6 . This is the only analysis that has been made of the sub- 

 stance. The method employed for its purification could not be ex- 

 pected to prevent oxidation of the pigment (Zopf showed that the 

 pigment readily bleached in the air) and would not insure freedom of 

 the product from alcohol and ether soluble impurities. Griffiths' re- 

 sults are therefore open to question and cannot be accepted as show- 

 ing the constitution of this important carotin-like pigment. 



Kremer (1919) has recently objected vigorously to the use of the 

 terms carotin and xanthophyll in connection with the lipochromes of 

 the Coleoptera, and, in fact, for the lipochromes of insects in general, 

 on the grounds that the older terminology of Krukenberg suffices 

 until the character of the animal lipochromes has been more accu- 

 rately determined. It is agreed, of course, that all scientific effort 

 must advance along conservative lines. At the same time one cannot 

 afford to be conservative to the point of being reactionary. 



Orthoptera. The facts concerning carotinoids among insect pig- 

 ments presented in the preceding paragraphs in themselves lend strong 

 support to the supposition that similar pigments exist in the yellow, 

 green and multicolored grasshoppers and other species belonging to 

 this group. The few experimental observations which have been made 

 are, however, inadequate for the proof of this supposition. Kruken- 

 berg (1880) recorded a brief study of these pigments in connection 

 with his attempt to explain Leydig's (1876) observation that the 

 common green locust, Locusta viridissima, changes to a brownish- 

 yellow color simultaneously with similar changes in foliage in the 

 autumn. Although he found that the chitinous layers in this species, 

 as well as Mirbius viridis and the common green grasshopper con- 

 tained specific green, yellow and red pigments, whose varying sensi- 

 tiveness to destruction by light was the probable cause of the color 

 changes noted by Leydig, the chemical properties of the pigments, 

 particularly their failure to show absorption bands, necessarily leaves 

 the question open as to the probability of carotinoid pigments being 

 involved in their coloration. It is true that Podiapolsky (1907) found 

 that a golden yellow solution was obtained by treating alcoholic ex- 

 tracts of green locusts with Ba(OH) 2 , and concluded that the pigment 

 thus secured was apparently identical with plant xanthophyll. Obvi- 



