CHEMISTRY OF INSECT COLOURS. 89 



species ; but, unfortunate!}'', we have no such clue to the chestnut 

 species in column 3, and, in fact, are entirely in the dark about 

 them. It is unnecessary to add any details here about these 

 " unaffected " chestnut species, since such have already been 

 given.* 



In the next place, this tabular arrangement emphasises the 

 remark made, in a previous paragraph, that among the chestnuts 

 increasing stability by no means connoted increased brilliancy, 

 for the species in column 2 can scarcely be considered more 

 brilliant or deep coloured than those in column 1. 



The species noted in column 2 call for no individual remark, 

 and we may, therefore, pass on to briefly consider those in 

 column 1 A. The two species, P. phloeas and P. virgaurea, appear 

 to me to be the most exact analogues of E. cardamines, since in 

 both cases, alike, the pigment has acquired an intense brilliancy, 

 and in both it is completely soluble, leaving a pure white wing ; 

 and just as this behaviour of cardamines may be compared with 

 the reaction of the similarly soluble jjaZe yellow of, e.g., species 

 of Terias, so, too, we may compare the behaviour of P. phloeas 

 and P. virgaurea with that of the pale brown displayed by 

 Coenonympha pamphilus — a brown that is equally soluble, and 

 equally leaves a pure white wing. The point which I wish to 

 make in drawing this comparison is that, just as we may consider 

 that a pale yellow developed into the brilliant orange of 

 cardamines, without any loss of solubility, so also a pale soluble 

 brown, such as that of C. pamphilus, was the precursor of the 

 brilliant colour of P. virgaurea. 



Turn we now to the species of Vanessa, which form a specially 

 interesting and important group. First, as to V. urticce : this is a 

 very important species, as forming a (coloric) link between so 

 many other species. The chestnut colour of V. urticce is readily 

 soluble, and can be seen oozing out and rising in dark vortices in 

 the solvent.! Now exactly the same result is observed in V. antiopa 

 and io. There can be no possible doubt that the same pigment 

 is present in all these three species. But — and here we come to 

 a very interesting point — whereas, in urticce, a white is produced, 

 in the other two species we find black. This puzzled me a good 

 deal in the early days of my experiments, but the explanation, of 

 course, is really very simple ; indeed, it was the study of these 

 species that first taught me that chestnut (and by inference, 

 yellow t) is not evolved/row, but on or in, white ; that its origin is, 

 therefore, genetically independent of white. This obviously clears 

 up the whole matter at once. The reason why the wings of io and 

 antiopa "are transformed from chestnut to black" by my reagents, 



* Entom. xxiii. p. 221. 



t I can recommend this as a singularly pretty experiment to any who are 

 interested in observing such things. 



\ I have, as yet, met with no yellow similarly evolved on a black wing ; but I 

 live in hope. 



