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THE AMERICAN NATURALIST [Vol. XLV 



caused by the action of a tyrosinase, the same cause pro- 

 duces the color pattern in Leptinotarsa. 



The Cause of the Color Pattern on the Elytra. — If the 

 pigmentation is due to the oxidation of a chromogen by 

 an enzyme, the color pattern may develop in four ways. 

 (1) The enzyme may be present over the entire body and 

 the chromogen may be localized. (2) The enzyme may 

 be localized and the chromogen secreted over the entire 

 body. (3) Both enzyme and chromogen may be localized 

 in those spots which form the color pattern. (4) Those 

 spots which lack color may be pigmentless because there 

 is an inhibitor to pigment production present. I have 

 found that in all probability the first hypothesis is the 

 true one, for, although the pigmentation is not much more 

 general when an unpigmented elytron is placed in a solu- 

 tion of tyrosinase, when such an elytron is floated upon a 

 solution of tyrosin the entire elytron becomes pigmented. 

 Apparently, therefore, the chromogen is localized and 

 the enzyme is secreted over the entire surface. 



Summary 



It has been shown that Tower's statements as to the 

 nature of the cuticula pigments, and the methods of pig- 

 ment formation, are based upon wrong interpretations 

 of his results, and upon errors in the application of chem- 

 ical data. The cuticula pigment is not an azo compound 

 but belongs to the melanins. 



The pigmentation of the elytron of the Colorado potato 

 beetle (Leptinotarsa decemlineata Say) is produced by 

 the interaction of an oxidizing enzyme of the tyrosinase 

 type, and an oxidizable chromogen. The color pattern is 

 caused by the localized secretion of chromogen. 



LITERATURE CITED 

 Bottler (1902). Die animalisehen Faserstoffe. Ein Hilfs- und Handbuch 

 fur die Praxis, umfassend Vorkommen, Gewinnung, Eigenschaften und 



stoffe. Nach dem gegenwartigen Standpunkte der Wissenschaft bear- 

 beitet. Leipzig. 



