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and collections I found that these leather-colours are most 

 decided in leaf-, wood-, and bark-eaters, such as Melolonthidae, 

 Dynastidae, even Elateridae, Buprestidae, and Cetoniadae, in 

 the absence of metallic coloration. It therefore at once 

 struck me that these colours may be due to the action of 

 tannin and its derivatives upon nitrogenous animal matter. 

 To test this supposition I took an elytron from each of 

 several beetles, especially Melolonthidae, steeped them for a 

 short time in a mixture of alcohol and ether to remove 

 anything greasy, and then placed them in a strong solution of 

 ferric nitrate. The first specimen in the box is a Melolontha 

 macalis which has thus been treated; the left elytron, which 

 is a decided black, was fixed in its place again, to show the 

 contrast with the original colour. This production of a black 

 colour with solution of iron is a very good test for the presence 

 of tannin. To confirm this result I treated other elytra with 

 a solution of potassium dichromate and with copper acetate, 

 and in each case I got the coloration which tannin is well 

 known to produce. I then applied the solution of iron to the 

 elytra of some carnivorous species, such as Carabus monilis 

 and Coccinella dispar. The action, as it may be seen in the 

 second and third specimens in the box, was practically nil. 

 Hence it would seem that carnivorous groups of insects do 

 not contain tannin in their tissues. I must now give a sum- 

 mary of the researches to which I alluded above, and which, 

 though undertaken with a quite different purpose, certainly 

 confirm my observations. M. Villon, writing to the Societe 

 des Sciences Industrielles de Lyon, states that he has for a 

 long time sought for tannin formed in the tissues or in the 

 secretions of an animal. He has found it in the well-known 

 corn weevil, < 'alandra granaria. He mentions that so far back 

 as 1810, Penant, of Bourges, found gallic acid, a body closely 

 connected with tannin, in the same insect. M. Villon grinds 

 up the weevils to a paste, extracts them with strong boiling 

 alcohol, evaporates the liquid to dryness, and finally, after 

 purifying the product, he obtains from 500 grammes of 

 weevils 15 grammes of a tannin which he calls fracticorni- 

 tannic acid. This substance possesses all the general properties 

 of tannin, and has been experimentally used in tanning, 



