SCIENTIFIC NOTKS AND OBSERVATIONS. Ill 



presence of a pigmentary material in the scale. These striations and 

 facets when wetted may conceivably lose largely their diffractive 

 and reflective power, and the result is that the brown or red, or 

 brown and red pigments then give tlie colour to the scale, until the 

 wetted surfaces become di-y and pregnant again. This is a hasty 

 supposition, but the only one that comes ready to hand to explain 

 the somewhat complex circumstances. I have often examined the 

 scales of T. rnhi under transmitted light, and it was this that led me 

 to believe that the scales must be pigmentary. I see that some four 

 years ago (Brit. Noct., vol. ii., p. xvi) I wrote : — " It is strange that the 

 greens of the undersides of certain Argynnidce, of Theda ruhi, and of the 

 uppersides of the various species of Procris are so readily convertible into 

 bro^vn, and yet we have to look upon them in the light of our present 

 knowledge, as probably 250ssessing but little pigment. The mere enclosure 

 of these species in a damp box changes their coloration to a bronzy or 

 red-brown, the original colour being restored by exposure to the air. 

 If these colours are in any way pigmental, the change is quite regular 

 genetically, but if not we must suppose that the presence of the vapour 

 which is deposited on the scales, alters the effect produced when the 

 light falls upon them. However, it is at joresent I'ather difficult to deal 

 with these colours." We appear to have got but little farther yet. I 

 can quite corroborate Dr. Riding's statement as to the greater chemical 

 activity of strong liquid ammonia in the presence of aqueous vapour. 

 The little Acidalia ochrata killed under the influence of the alkali alone 

 quickly recover their colour, but in the presence of water vajDour the 

 loss of colour is both gi'eater and more j^ermanent. It was the careful 

 examination of the show-cases at the doors or in the windows of our 

 London dealers that first convinced me that many so-called metallic 

 colours, usually considered non-pigmentary, were, indeed, highly 

 pigmentar}'. As Mr. Burrows states (and I believe I long ago made a 

 similar observation) the exposure of such insects to the heat and light of 

 the sun does not alter the form and structure of the scale. Such colours 

 then as are due to scale structure, whether caused by refraction, 

 diffraction or interference, must be permanent ; colours, however, which 

 are dependent upon a pigmentary substance, Itecome modified or changed 

 entirely, as the pigmentary matter undergoes dessication. — J. W. Tutt. 

 Jan. 28th, 1895. 



Phytophagic Species. — In American literature a number of obser- 

 tions are recorded upon what may be called " phj^tophagic sj^ecies," 

 where some small change, in larva or imago, is apparently correlated 

 with a difference in the food plant. It is often the larva alone which 

 seems to differ' s])ecifically. Tlie late Mr. B. D. VValsli was the 

 pioneer in observations in this direction, and his jjapers ma}' be found 

 in the Proc. of the Ent. Sue. Philadelphia and of the Boston Sac. Nat. 

 Hiatorij. The common Halisidotatesselaris appears in two phytophagic, 

 larval iovms—aiitijjhoht, Walsh and harrisii, Walsh. These two larval 

 types differ in the colour of the hair pencils ; in the first these are 

 black, in the last orange. The moths do not differ, hence the names 

 have no standing as applied to captured imagos. They should only be 

 applied to collections of larvae. In another instance Mr. Walsh 

 believed that he had verified the existence of a phytophagic species in 

 the large moths of the genus Sphiiujicampa {Adehcephala, Bdv.); but, 

 as I have shown, in this case the experiments were defectively con- 

 ducted ; the moths of Walsh's hicolor came from the same kind of 



