igii] Ross Aiken Gortner 209 



of an insoluble tyrosinase was found. Soluble tyrosinase is, how- 

 ever, present in relatively large amounts. A possible explanation 

 of the meaning of the color pattern in the elytra of this beetle has 

 been found. If the elytra be removed before the color pattern 

 develops (just after the beetle has emerged from the pupal shell) 

 and floated on vvater exposed to the air, the normal color pattern is 

 produced. If, however, the water is replaced by an aqueous Solu- 

 tion of ty rosin the entire elytnim is colored black. It would thus 

 appear that the color pattern is caused by the localised secretion of 

 chromogen and that the secretion of the oxidizing enzyme is uni- 

 form over the entire elytrum. 



In the periodical cicada, or seventeen-year locust, the mode of 

 pigment formation is somewhat different. When the mature cicada 

 emerges from the pupal shell the body is creamy white with the 

 exception of the reddish eyes and two black spots on the prothorax. 

 In a short time the creamy tint deepens and in a few hours the 

 entire body is jet black. I was unable to find a tyrosinase in the 

 body-filling of either the pupae or adult cicadas although an oxidase 

 of some sort was present.^ It was found however, that the outer 

 surface of the body was moist and sticky, and by immersing the 

 newly emerged adult in water, this moist, newly secreted, cuticula 

 was dissolved and the Solution was found to contain both a tyrosi- 

 nase and a chromogen. It seems very probable that the tyrosi- 

 nase is secreted and poured upon the surface of the body together 

 with the new cuticula, and, indeed, it is not improbable that the 

 entire new cuticula may be formed by the action of the tyrosinase 

 on a chromogen. The same difference in solubility is observed 

 between the newly secreted cuticula and the mature cuticula, as is 

 found between the enzyme and chromogen, and the final pigment. 



It would appear that in all cases where the origin of the pigment 

 has been carefully investigated the production of melanin has been 

 found to be due to the interaction of an oxidizing enzyme and an 

 oxidizable chromogen, and it is very probable that all melanotic 

 pigments originate in this manner. Even admitting the truth of 

 this hypothesis several problems still remain to be soJved : ( i ) The 

 cause of albinism, (2) the sudden appearance of pigment in a color- 



* Extracts of the body-filling oxidized a Solution of guaiacol to an orange 

 brown color. 



