﻿CHEMISTRY OF INSECT COLOURS. 185 



II. Acetic acid Strong. 



Oxalic acid Saturated solution. 



Tartaric acid 25 per cent, solution. 



Gallic acid Saturated alcoholic solution. 



III. Ammonia Strong (i.e., the usual solution of 



the gas). 

 * Sodic hydrate 25 per cent. 



Ditto 10 per cent. 



f Potassic hydrate 25 per cent. 



Ditto 5 per cent. 



IV. | Phenol 50 per cent, alcoholic solution. 



§ Trinitrophenol Saturated solution. 



Tannin (Strength of solution unknown.) 



V. Potassic cyanide Strong solution; exact strength 



not known. 

 Argentic nitrate 25 per cent, solution in 50 per cent. 



alcohol. 

 Potassic permanganate About 7 or 8 per cent., probably. 



Potassic dichromate x Abandoned very quickly, as being 



Potassic iodide. ite ugdfla J 



Potassic lerro-cyanide J 1 



I might add that, having originally delusively anticipated the 

 most important results from the organic acids, I had proposed to 

 use various others of these, such as succinic, malic, citric, 

 benzoic, lactic, formic, &c. ; but finding quickly how useless the 

 organic acids were, I relinquished this intention. 



Now, regarding the action of these various reagents, the first 

 thing to note is that most of them are either useless or super- 

 fluous. Beginning at the bottom of the list, the salts are either 

 quite without action, or— e. g., potassic cyanide — very feebly 

 imitative of stronger reagents, and therefore wholly superfluous. 

 A peculiar effect produced on one or two colours by a strong 

 solution of argentic nitrate will be referred to subsequently. 

 In the next class (IV.), I had hoped to find some striking 

 results ; but the action, where any occurred, was simply feebly 

 imitative again, and so superfluous. Among the alkalis, ammonia 

 was somewhat disappointing. I had expected it to be by far the 

 most active reagent of the set, but it proved often less efficacious 

 than the others. The action of all these five reagents was the 

 same, and therefore several of them are evidently superfluous. 

 But the most surprising result was that (with, I think, one 

 exception) the action of these alkalis was identical with that of the 

 acids. By this, I do not mean that the same colour in the same 

 insect was always affected equally by acid and by alkali, but that 

 whenever any action followed it was always the same, and differed, 



* Caustic soda. t Caustic potash. 



! " Carbolic acid." §~ " Picric acid." 



