THE LIFE-HISTORY OF A LEPJDOPTEftOtS INSECT. 83 



consisted originally of Uibercle- and hair-bearing segments. It would be 

 interesting to know whether the newly-hatched larvseof such species as 

 Liinenitis sibi/Ua and Vanessa pohjchloros, in which the posterior head- 

 segment of the adult larva bears fleshy spikes, give us characters wliich 

 tend to show the latter to be of the .same origin and significance as the 

 spines of the thoracic and abdominal segments, that is, whether they 

 bear tubercles on this head-segment which have a similar morphological 

 value. The body-segments are usually sub-divided into subsidiary rings, 

 or sub-segments, which move more or less freely upon each other, and 

 in some cases these sub-segments prove of great classificatory value. 

 The sub-segments are sub-divided again into still smaller solid portions 

 which have a certain amoiint of freedom. These are technically termed 

 sclerites (skleros, Gr. = hard). The sub-segments themselves are fre- 

 quently separated by ill-developed membranous rings, somewhat like, 

 but generally less clearly defined than, the intersegmental membranes. 



gCIENTIFIC NOTES & OBSERVATIONS. 



Discussion ori the ]\Iatupe of certain Colours. 



{Continued /rem p. 40.^ 



I think a great many of our respective argnments have been wasted 

 because we did not start from any fixed basis (the whole matter 

 having arisen from Dr. Riding's remarks about Hepialus humuJi), and it 

 will perhaps make things a little clearer if I state my oj^inion : — 

 Pigment is used generally as a term for the colouring matter of insects, 

 and I want to confine its use to such colouring matter as may be 

 i.'^olated. Those substances which by their colour impart a hue to animal 

 and A^egetable tissues, and which I consider pigments are : Htemo- 

 globin and derivatives from blood ; bile pigments ; melanin, and others 

 of a similar nature ; the pigment of the human skin and retina, and 

 also that of other vertebrates. It is merely a matter of definition, but 

 an outsider would think, if reading any of the various articles on this 

 subject, that the so-called pigments of the butterfly's wing are as 

 tangible bodies as those above-named. To Dr. Riding's question, 

 " When Ave use the word jDigment, are we not forgetting that there is 

 in reality no such thing as colour at all? " I would reply that pigment = 

 jiaint, or that witli which any object is coloured ; and that as to colour, 

 it is the result of the visual judgment, which varies consideral)lv, as 

 evidenced by colour-blindness, and is as real as any other subjective 

 sensation. Dr. Riding objects to my refractive theory with regard to 

 the change of the green in Thechi rnhi. There is an insect Avhose green is 

 almost similar to, thougli more iridescent than, that of Thecla rubi — I refer 

 to Miselia oxijacmithae. The green part of tliis insect behaves in a similar 

 manner to that of T. rubi, and Mr. Tutt (British Noduce, vol. ii.) has (juoted 

 other instances. When I called the green a " potential " colour, Avhat I 

 meant was tliat, as I understood Dr. Riding's definition of the term, it 

 would fall under that head. Personally, I sliould call it a colour 

 resulting from refractive powers of the superficial layers of scales. If 

 it were a suljstantive colour, water would not make any difference, or 

 at any rate would only make it appear a little darker ; but iu this case, 



