u 



THE ENTOMOLOGIST. 



Still acid to the tongue, I again washed, and with this result : 

 jacohcBcB became red ; nupta flesh colour ; caia remaining still 

 nearly yellow. But on examining them after three days, they 

 were all of the natural red : after another four days they 

 were still the same, and finally, at the end of another week, 

 the red was still permanent. Here the observations were 

 stopped. 



Wings of S. ocellatus and P. aiJollo (which had already been 

 once yellowed by HCl and had afterwards recovered their full na- 

 tural colour) were treated just as the foregoing three species. The 

 first washing restored the full red to apollo, and the pink some- 

 tvhat to ocellatus (entirely removing the yellow anyhow). A 

 week later apollo was found still of its full natural colour, 

 ocellatus being a very faded slightly pink tint (the colouring 

 matter probably having been nearly all removed by this time). 

 The lapse of another week produced no difference, the restored 

 natural colours being permanent. 



Now these experiments had already clearly proved several 

 points : firstly, that the reversion was not due to treatment with 

 alcohol ; and secondly, that the whole secret lay in removing the 

 acid — in which fact alone there evidently lay the virtue of washing 

 the wings ; so that the yelloio was permanent only so long as the 

 iving ivas actually acid. Here was an entirely novel and unlooked- 

 for phenomenon, — something quite different from any former 

 experience with other insect colours ; and I would draw the 

 reader's special attention to this peculiarity, to which I must 

 revert when seeking to explain these results. Thirdly, it is 

 clearly proved, so far, that the yellow produced by nitric acid is 

 permanent and immovable. The question then arose : Which is 

 typical of acid behaviour generally, HCl or HNO3 ? This could 

 only be settled by further experiment. Fourthly, it was at 

 present somewhat uncertain how far washing could be altogether 

 dispensed with, and the same result obtained as a mere time 

 effect. _ 



Wings of Z. Jilipendulce were treated with dilute sulphuric 

 acid (about 45 per cent.) for (A.) one hour and (B.) two hours. 

 A., on being washed, was restored to a very faded red, which was 

 still permanent after seven days. B. was also restored in the 

 same way ; examined two hours or so later it was found fairly 

 yellow, and acid to the tongue ; further washing restored it to the 

 full red, which was still permanent in seven days' time. A wing 

 of S. ocellatus was treated as A., and washing restored a little pink 

 (?), which was unaltered seven days later. 



These fresh results clearly pointed to the necessity for 

 further investigation, and I therefore determined on an extensive 

 set of experiments, in order to thoroughly clear up this question. 

 Wings of the following six species were selected, viz., F. atalanta, 

 Z. Jilipendula, E. jacohcece, Deiopeia bella, C. hera^ and C. nupta, 



