CALLOPHRYS RUBI. 99 



examined which presented exactly the effects noted by Dr. Biding in 

 the scales of C. rubi, though much exaggerated ; by reflected light it gives 

 a brilliant green, but by transmitted light a good red ; and, in both 

 cases, there can be no doubt but that the red is the true colour. The 

 green is the effect of the dry pigment by way of reflection." Riding 

 still, however, is inclined to consider that the green is solely due to 

 pigment, and he states (op. cit., p. 205) that " there seems to be green 

 and red pigment in the scales, the green being superficial. When 

 white light strikes these green granules, a great part is reflected from 

 their external surface as white light, which, however, carries with it 

 some green that has been reflected from the posterior surface after 

 penetration. The white light, penetrating deeper, meets with the red 

 granules, but, owing to the dark background, most of it is absorbed. 

 What little red is returned mixes with its complementary green, and 

 forms white light, which slightly diminishes the intensity of the 

 reflected green. When light is transmitted there is much more red 

 light, part of which forms white light by uniting with the green, and 

 the remainder meets our eyes as red. When water is added, the 

 amount of superficial reflected light is very much diminished, because 

 the light passes through water instead of air (a dense medium instead 

 of a rare one), consequently more red light, proportionately, is reflected, 

 part of which combines with the weaker green to form white light, 

 and the rest appears to us as red." He then asks : " Were it connected 

 with the interference of light from the stria? of the scales, would not the 

 colour vary with position as in Bithys querciis ? " This is where the 

 matter was left in 1892, and where it stands now. How the change is 

 really brought about we do not definitely know, nor do we know the real 

 nature of the green colour. In 1882, Tyndall wrote : " The question 

 of absorption of light, considered with reference to its molecular 

 mechanism, is one of the most subtle and difficult in physics ; we are 

 not yet in a condition to grapple with it, but we shall be by-and-by." 

 It is very doubtful whether we are any nearer doing so now than was 

 Tyndall a quarter-of-a-century ago. 



Pathological examples. — The following pathological specimens 

 have been noted : — 



1. — A nice example, in which the outer half of all the wings is partially 

 bleached, though more so in the case of the fore- than of the hindwings. Captured 

 Isle of Purbeck, Dorset, June 13th, 1888 (Bankes, Ent. Mo. Mag., xxv., p. 307). 



2. — A ? taken May 16th, 1883, has the colour before the margin of the fore- 

 wings (especially round the apex), and the right hindwing of an ashy-grey colour 

 (Fuchs, Jahrb. Nass. Ver. Naturk., xliv., p. 211). 



3. — All the wings bleached towards the hindmargin (Webb Coll.) (Mosley, 

 Nat. Journ., 1896, p. 7). 



4. — A cream spot on the forewings. Taken at Wrotham, in Kent, in 1901 (Carr). 



5. — The upperside of hindwings with a wide border, 2mm. in breadth, of the 

 ground colour, extending round the hindmargin, the remainder of the wings dirty 

 yellow (Rothke, Gross. -Schmett. v. Krefeld, p. 18). 



6. — The upperside of the hindwings yellow-brown before the border. Taken in 

 May, 1903, near Plauen in Voigtlande(Winckler, Iris Dresc?e?i.,xviii., p. 25, pi. i., fig. 3). 



7. — The base and margin of the upperside of the hindwings bright yellow 

 (Bergstrasser, Nomenclatur, pi. 71, fig. 7). 



8. — The upper wings, which are usually of an uniform brown, banded 

 with a beautiful pale irregular-edged bar. Captured at Morlaix, Brittany, on May 

 17th, 1867 (Piffard, Ent. Mo. Mag., iv., p. 35). 



9. — All the wings on the upperside, towards the outer margin, light ash-grey, 

 especially marked on the forewings ; the remainder of the wings of a typical brownish- 

 black. Taken at Geppersdorf on the Rummelsberg, in the district of Strehlen 

 (Schultz, Soc. Ent., xix., p. 9). 



