122 



COI.ORATION IN I^^PTINOTARSA. 



Some of these pigments are very unstable and break down on exposure to 

 light or at death, while others are of great permanence and are soluble only 

 after the most vigorous treatment with strong mineral acids. The colors, 

 their location in the body, their solubility, and degree of permanence are sum- 

 marized in the following table : 



Chemical 



or 



pigmental 



colors. 



(a) Cuticula or 

 dermal col- 

 ors. 



Black, dark 

 brown, brown, 

 straw yellow. 



I^ocated in the 

 primary cuti- 

 cula. 



{b) Hypodermal 

 colors. 



(c) Subhypoder- 

 mal colors. 



(I) 



(2) 



f Chrome yel- 

 i low, red, 

 ■{ vermilion, 

 I scarlet, 

 I blue. 



Located in hy- 

 p o d e r ni a 1 

 cells as gran- 

 ules. 



Green, 



yellow, 

 white. 



Located in or 

 between the 

 h y podermal 

 cells as a dif- 

 fuse pig- 

 ment. 



(Green, 



-< yellow, ■{ 

 j white. I 



f Located in body ^ 



cavity in fat ! 



i body andf 



L hsemolymph. J 



Derived 

 pigments. 



Permanent, insoluble, or solu- 

 ble only on long standing in 

 water, alcohols, ethers, oils, 

 weak acids, or alkalis. Solu- 

 ble on standing or with heat 

 in strong mineral acids and 

 alkalis, with dissolution of 

 the cuticula. 

 Permanent, insoluble, or solu- 

 ble with difficulty in water, 

 alcohol, weak acids, or alkalis. 

 Soluble in ether and other 

 fatty solvents. 



' Not permanent; 

 fade at death or on 

 exposure to light. 

 Soluble in water, 

 alcohols, etc. 

 I Chlorophyll and 

 I xanthrophyll de- 

 L rivatives. 

 Not permanent. Lar- 

 val colors. Soluble 



Derived 

 pigments. 



in water, 

 etc. 



alcohol. 



The chemical composition of the compounds which produce color has been 

 studied by Krukenberg by spectrum analysis, and by this and other methods 

 by Hopkins, Griffiths, Urech, Poulton, Mayer, Tower, Dewitz, Enteman, and 

 others. The cuticula pigments are diffuse pigments elaborated from the pri- 

 mary cuticula through the action of an enzyme which I have isolated and 

 called chitase. The product of this enzyme action is an azo compound, oxy-, 

 di-, or amido-azo, and shows all the characteristic reactions of this group 

 of organic compounds. It is maintained by Enteman that the pigment is 

 elaborated in the hypodermal cells, and passes out through the pore canals of 

 the cuticula to the primary cuticula, where it finally remains ; while others, 

 working on a wider range of material, find that it arises as a diffuse pigment 

 through the action of an enzyme which has been elaborated as the result of 

 chromatolysis of the nuclei of hypodermal cells upon the primary cuticula 

 when in a soft condition — the action of the enzyme being akin to coagulation 

 or gelatinization and the products being hard, stiff cuticula and the azo 

 compounds. 



The pigments which produce the hypodermal colors have been studied by 

 Krukenberg by spectrum, by Zopf and Tower in the hypodermal cells proper, 

 and by Hopkins, Griffiths, Urech, Mayer, Von Linden, and others in the scales 

 of Lepidoptera. In the hypodermal cells proper Zopf and Tower find that 

 the colors in Coleoptera, Hemiptera, Lepidoptera, and Hymenoptera are due 

 to granules of pigment of a fatty nature. Some of these were shown to be 

 lipochromes by Zopf in Coccinellidae, and by Tower in other families of Cole- 



