484 Prof. E. B. Poulton on the Mimetic N. American 



the last spot but one is twisted into a much, closer coinci- 

 dence with the inner border of the hind-wing band. As 

 regards the position of the last spot but one, lorquini goes 

 much further than calif ornica, the direction of the inner 

 border of the fore-wing spot coinciding with the outer 

 border of the hind-wing band (Figs. 6-8). 



Apart from the orientation of the last spot but one in 

 the band of the fore-wing, the very characteristic hour- 

 glass-like form seen ia greater or less perfection in all 

 the figures on Plate XXV is probably an ancestral feature. 

 There appears to be no doubt that the indentation of the 

 inner side of the spot tends to be obliterated and replaced 

 by a straight contour in hredowi (compare Figs. 2 and 3 

 with 4, 5 and 9). In this respect the northern form 

 is probably ancestral. At any rate an approach to lorquini 

 in this feature is unlikely ; for in lorquini itself the inner 

 contour is less indented than in californica. 



The fact that the break in californica approaches but 

 does not equal that of lorquini, attaining in fact about the 

 condition of wcidcmeyeri (see Figs. 1 and 10), supports 

 the conclusion that in this respect lorquini acts as a model 

 and californica as a mimic. 



The step-like break, together with the more out- 

 ward position of the spot below the end of the cell in 

 californica, tends to give the band of the fore-wing an 

 irregular zigzag W-like appearance, suggesting the form 

 which is more fully and symmetrically attained in lorquini. 

 The example of hredoioi, represented in Fig, 9, is in the 

 opposite condition, with a comparatively straight fore-wing 

 band, while the specimens seen in Figs 4< and 5 are inter- 

 mediate. The outward displacement of the spot below the 

 cell of californica promotes this superficial resemblance to 

 lorquini, in spite of the fact that the corresponding spot of 

 the latter occupies a more inward position. It produces 

 this effect by increasing the angulation of the irregular 

 zigzag formed by tlie fore-wing band. 



d. The external hordcr of the hind-wing hand. — The fifth 

 spot (from the costa) of the hind-wing band of californica 

 projects beyond the rest of the outer border to a greater 

 extent than in hredowi, and thus disturbs the regular 

 straight or slightly concave sweep which is so character- 

 istic in the southern form. Although resembling no par- 

 ticular feature of lorquini, the difference probably promotes 

 a general superficial resemblance to the distinctly convex 



