COLORATION IN POLISTES. 51 



Bismarck brown and vesuvin brown were also treated with concen- 

 trated H 2 SO 4 . In neither case did the dye wholly dissolve. Dilution 

 produced a rich golden-red solution, threw 'down a deep red-brown 

 residue, and finally turned the solution a light reddish yellow. A.S the 

 solution was further diluted, it approached the color of the solutions 

 of Polistes already described, until a stage was reached where the color 

 was identical with the solution of dark chitin of P. rubiginosus in H 2 SO 4 . 



I pulverized the skeletons of two specimens of P. lineatus in a mor- 

 tar and afterward treated them with dilute HC1. The pieces of chitin 

 remained intact, but a colored solution was obtained which was similar 

 to a solution of Bismarck brown in HC1. 



Following is a comparison of the results obtained by the spectro- 

 scopic analysis of the pigments of Polistes and the yellow and brown 

 azo-compounds. 



Solution of dark P. rubiginosus in dilute H 2 SO 4 cuts off almost all the 

 rays from the violet to the blue end of the spectrum, leaving only a 

 slight thin line near the green. There is an indication of absorption 

 bands in the yellow. Solution of Bismarck brown in H 2 SO 4 , same 

 degree of dilution, cuts off same end of spectrum and to exactly the 

 same degree. The absorption band in the yellow is more marked. 

 The solution is also slightly more orange yellow than that of the wasp 

 pigment, which inclines slightly to brownish. 



Solution of the pigment of P. lineatus in dilute HC1 cuts off a zone 

 extending from the violet to the blue end of the spectrum, also the 

 red end, and gives a marked absorption band between the orange and 

 the yellow zones. Solution of Bismarck brown in HC1 is yellower 

 than that of lineatus, cuts off the ends of the spectrum to the same 

 degree, and has an absorption band in the yellow. Solution of P. vari- 

 atus in H 2 SO 4 is intermediate in orange-yellow tint between the solution 

 of P. rubiginosus and Bismarck brown in H 2 SO 4 and gives a spectrum 

 similar to that belonging to these two. 



A further series of tests was made both upon the yellow hypodermal 

 color of the adult and the developing colors of the pupa, but no reac- 

 tion was obtained that indicated these to be proteid in their nature or 

 related to uric acid, as has been found to be the case in Pieridie (Hop- 

 kins, 13). 



Boiling in moderately concentrated HNO 3 did not change the color 

 of the yellow hypodermal pigments. This treatment imparts to proteid 

 a yellow flocculent appearance, and subsequent treatment of both the 

 proteid and the yellow pigment in HNO 3 with NH 4 OH gives them a 

 rich orange color. This is called the xantho-proteid reaction. 



