134 COLORATION IN LEPTINOTARSA. 



agitation. By this method all tissues were removed and pure, or nearly pure, 

 quantities of the primary cuticulawere obtained and subjected to various tests. 



Ledderhose showed that "chitin," in cold, concentrated solutions of HCL 

 or H 2 SO <t when dropped into water at ioo C, gave glucosamine or glucose, 

 which reduced copper suboxide in alkaline solution. This indicates, accord- 

 ing to Ledderhose, that chitin is an amido-derivative of a carbohydrate. I 

 have tried the following experiment with the primary cuticula prepared as 

 above: Five grams of the dry primary cuticula were dissolved in cold 

 concentrated HCL and the same amount in cold H 2 S0 4 . One cubic 

 centimeter of each of these was then dropped into distilled water at ioo C. 

 and kept boiling for ten minutes, the solution being made alkaline with 

 Na 2 C0 3 and tested with copper suboxide. No reaction was observed, and it 

 is certain that in this case there was no production of glucosides. Dilution of 

 the solution of primary cuticula in concentrated HCL or H 2 S0 4 with water, 

 when tested with copper suboxide in alkaline solution, gave no reaction, 

 thus showing the absence of glucosides or related carbohydrate compounds, 

 although Strecher showed that chitin, dissolved in concentrated HCL or 

 H 2 S0 4 , diluted with water, gave grape sugar and nitrogenous decomposition 

 products (NHj). 



Chitin prepared from adult beetles by grinding, maceration, washing, and 

 boiling in weak acids (HCL, HN0 3 ,'h = S0 4 , or KOH, or NaOH) until 

 white, as done by Ledderhose and others, gives a product which is composed 

 almost entirely of secondary cuticula, as I have before shown. If now 0.5 

 gram of this be dissolved in the cold in concentrated HCL or H 2 S0 4 , diluted 

 with water, and the whole made alkaline and tested with copper suboxide, 

 beautiful reductions of copper take place, showing the presence of abundant 

 glucosides. It appears from these two experiments that from the primary 

 cuticula no glucosides were produced in decomposition, whereas from the 

 secondary cuticula there were abundant indications of them. 



When dried primary cuticula was boiled in water under pressure for a long 

 time, the result was a nearly complete solution, from which alcohol precip- 

 itated a colorless, gelatinous mass, which was, on further examination, found 

 to give reaction tests for both gelatinates and albumen. No trace of glu- 

 cosides was obtainable in this series of reactions. On the other hand, when 

 secondary cuticula was boiled under pressure with water for a long time, the 

 solution of a part was effected, and of the remainder when boiled in a slightly 

 alkaline solution. This solution gave strong reaction for glucosides and 

 carbohydrates, with traces of albumen and gelatinates. 



We conclude from these experiments that the chitinous portion of the 

 integument of these beetles is composed of two kinds of material recognized 

 in sections by Vossler and Tower to be, the one an albumino-gelatinate, the 

 other a carbohydrate or an amido-derivative of these, giving as decomposi- 

 tion products glucosides with traces of albumen and gelatinates. At present 



