﻿CHEMISTRY OF INSECT COLOURS. 219 



transparent under treatment ; and in Hepialus humuli nearly 

 every reagent removed the white appearance, and left a more or 

 less transparent wing. Of a doubtful reaction with Amphidasys 

 betularia I will speak later, when discussing these results.* 



There is also a special and independent series of experiments 

 that I have made as a forlorn hope of discovering something 

 about this uncompromising pseudo-colour. It was intimated in 

 section in. of my paper, which appeared last month, that an attempt 

 would presently be made to discriminate between the various 

 whites by staining with iodine. Since that passage was written, 

 I have conducted a set of experiments with this reagent ; and in 

 order to make the investigation more thorough, I made parallel 

 sets of experiments with four other staining reagents, viz., 

 logwood, rosein, methyl aniline green, and methyl aniline violet. 

 These experiments were made under the same conditions as all 

 previous ones, except that the wings were first damped with 

 alcohol. After one hour's exposure, the staining fluids were 

 thoroughly washed off (no such easy matter), and then the 

 staining effects on the wings were noted. 



Logwood. — The results with this were so negative and un- 

 satisfactory as to deserve no record. 



Rosein. — Since this stained everything red indiscriminately, 

 it is also useless to detail any particulars. 



Methyl aniline green and violet, and iodine. — The results 

 yielded by these reagents are recorded in the annexed table. 

 The iodine was a 16 per cent, solution in absolute alcohol, but 

 the working was rendered less quantitative owing to the partial 

 evaporation of the alcohol after being exposed some time, and 

 the consequent necessity of adding either fresh alcohol or fresh 

 iodine solution. In all probability, however, the total staining 

 effect was produced in the first very few minutes. As to the 

 strength of the two methyl aniline stains, I cannot speak. They 

 were originally obtained by me, as solutions, for use in botanical 

 histological work, and are such as are always sold by microscopic 

 dealers. I found it necessary to dilute them in these experiments. 



The significance of the results will be discussed later, in the 

 proper connection; and I need merely draw attention here to the 

 effect on P. bi'assicce and on M. galatea. 



* I noticed in one or two cases, when experimenting on other colours, that the 

 very delicate white fringes which often border the wing were turned yellow by 

 ammonia, potassic hydrate, and even one or two acids. Instances are afforded 

 by Lycaina artaxerxes and L. cor y don (and also by Melitcca athalia, with one or 

 two reagents, anyhow). This yellow did not seem to me, however, in all cases so 

 permanent as was the yellow produced in M. galatea. I may as well add to the list 

 given above the name of a tropical butterfly, Papilio menesthenes, one of a number 

 kindly sent to me by Mr. Geo. C. Griffiths. The wings of this are marked beneath 

 by largo patches of white, represented by cream colour on the upper side. The 

 appearance of this white led me to suspect that it might give the galatea reaction, 

 and I therefore tested it with the usual reagents. To my disappointment the results 

 were all nil; and galatea is, for the present, left in her almost unique position. 



