364 



was still more considerable than in machaon. This led me tO' 

 ask if we might not be justified in regarding these knobs as 

 something more than a mere ornamentation, viz. the rudiments 

 of sense-organs for the perception of light. Should this 

 hypothesis prove to be well founded, then the same might 

 perhaps be assumed for the inner series of spots in Vanessidœ-, 

 though here the regression from the original functional structure 

 must have reached a far deeper level. 



I have not yet been able to test the probability of this 

 suggestion, but I wish to point out that Ph. Vogel, in his paper 

 on the distribution of the sense-organs over the wings of the 

 Lepidoptera, Zeits. Wiss. ZooL, xcviii (1911), indicates the presence 

 of " Sinneskuppeln " along the course of the veins and especially 

 at their outer ends, where they meet the lateral wing-border. 



Papilio podalirius (fig. 6). 



Though the general aspect of the wing-cases of podalirius 

 is remarkably difíerent from that of machaon, they are in fact 

 built and ornamented on the same principles, and show the 

 same peculiarities. 



The net of the wing-ribs is conspicuous by reason of its light 

 colour against the darker brownish tint of the remaining wing- 

 surface. Though at first sight one might think that this ground- 

 colour was very evenly distributed, it is not difficult to dis- 

 tinguish triangular interveinal marginal areas of a somewhat 

 darker hue. In the middle of the base of each triangle a small 

 twig-like knob sprouts inward from the marginal vein, and 

 outward into the interval separating the margin of the imaginai 

 wing from that of the pupal. 



Thais polyxena (fig. 7). 



It seems to me a remarkable fact that, while there exists 

 a considerable difference between P. machaon and podalirius, 

 the wing-sheath pattern of the former is repeated almost to 

 identity on the pupa of Thais polyxena. This fact I consider 

 as an important proof of the deep significance of this pattern. 



