4GS Prof. E. B. Poulton on, the Mimetic N. American 



would interfere with the mimetic resemblance to 2~)hiJcnor. 

 On the surface of the hind-wing the melanic transform- 

 ation is accompanied by a great development of the 

 iridescent blue scales, extending inwards into the cell, and 

 also upwards to the costa and beyond into the neighbour- 

 hood of the anal angle of the fore-wing. In the few 

 specimens I have had the opportunity of examining the 

 colour of these scattered scales was bright blue and not 

 bluish-green as in the submarginal region of the under 

 surface. The yellow marginal and submarginal markings 

 of the upper surface remain and contribute towards the 

 resemblance to 'philcnoi^ although the submarginal series 

 is much nearer to the border of the wing than in the 

 primary model. As regards the yellow colour, the tvrnus 

 form is the least perfect of the three Papilionine mimics; 

 for the submarginal spots of troilus (although yellow in 

 the more ancestral non-mimetic 2^<'J<^'^n<:dcs) have gained a 

 peculiar bluish-green colour in mimicry of 2>hilenor, while 

 those of the female astcrius have undergone a slight 

 modification in the same direction. 



In another very important element, however, the under 

 surface of the turnus female is far nearer to philenor than 

 are any of the other Papilionine mimics : — the existence 

 of a single instead of a double row of bright orange-red 

 submarginal spots on the hind-wing, although these are 

 nmch closer to the margin of the wing than in the primary 

 model. On the other hand, a second inner row of such 

 spots is not present in the male or the ancestral female 

 which resembles it. In the position of this inner row 

 four wedge-shaped dull red marks are to be seen in the 

 ancestral pattern, and the persistence of these, intensified 

 by contrast with the dark ground colour, in the tuo'nus 

 form, is probably related to the presence of the inner row 

 in astcrius and troilus. They certainly interfere with the 

 resemblance to philenor. 



Each of the first four orange spots (counting from the 

 costa) on the hind-wing under surface o( j^hilcnoi^ is edged 

 with glistening white on the side towards the apical angle 

 of the wing, the fifth is edged on both sides, the sixth 

 towards the anal angle but not on the other side, while 

 the seventh is not edged at all. In this respect the pattern 

 of turnus, although by no means identical with 2^hilcnor, 

 approaches the latter more closely than do any of the 

 other Papilionine mimics. 



