260 ME. E. B. POULTON ON THE EXTEENAL 



Fig. 19. X 50. The seventh and eighth segment (from the base) of the antenna of the female imago 

 of Orgijia antiqua. The structure is seen to be very degenerate ; the small rami possess two 

 terminal bristles, but no traces of sensory hairs are seen. 



Fig. 20. Natural size. The left antenna of the male pupa of Centra vinula. 



Fig. 21. Natural size. The left antenna of the female pupa of Cerura vinula. 



Fig. 22. Natural size. The left antenna of the male imago of Cerura vinula. 



Fig. 23. Natural size. The left antenna of the female imago of Cerura vinula. It is very interesting 

 to find that the same relation as that illustrated above, between degenerate female antennae 

 and the corresponding pupal organs^ also obtains in species where the degeneration is com- 

 paratively slight. 



Fig. 24. X 5-25. The male pupa of Nyssia zonaria, as seen from the left side and also somewhat from 

 the ventral aspect. The pupal antennte are seen to be large. 



Fig. 25. x5'25. The female pupa of Nyssia zonaria, seen from the same aspect. The pupal antennae 

 and wings, although smaller than those of the male, are seen to be well developed. 



Fig. 26. X 9. The left antenna of the male imago of Nyssia zonaria, as seen from above. The upper 

 rami are distinctly shown, the lower only for part of the length of the organ. 



Fig. 27. X 9. The left antenna of the female imago of Nyssia zonaria, as seen from above ; the number 

 of rings indicated is only approximately correct. The curvature of the antenna was the reverse 

 of that in the male, although this diiSerence is compensated in figs. 26 and 27 by the base of 

 the male antenna being placed over the tip of that of the female and vice versa. The dege- 

 neration of the female antenna is seen to be very complete, although the corresponding pupal 

 organ is by no means small. 



Fig. 28. X 5-25. The left fore wing of the female imago of Nyssia zonaria. The minute size of the 

 structure is well shown, especially when it is compared with the corresponding part of fig. 25, 

 which is magnified to an equal extent. Hei-e also we meet with evidence that the degeneration 

 of the female wing is very recent ; for the pupal wing is but little smaller than that of the 

 male, withiu which fully formed and functional wings are developed. 



Fig. 29. X 50. The antenna of the larva of Pieris brassicoe. The figure is added for comparison with 

 the details of the imagiual and pupal antennae shown upon this Plate. 



Plate XXVII. 



The Wings of Lepidopterous Pupie compared with those of the corresponding Imagines. 



All the figures have been unavoidably reduced by the lithographer, and are much smaller than the sizes 

 indicated. The deviation from the originals appears to be about 15 per cent. 



Fig. 1. X 7. The left wings of the female imago of Cheimatobia boreata. Although the wings are very 

 small and of course utterly useless, the figure shows that they retain distinct traces of a 

 jiattcrn which suggests that developed upon the functional wings of the male. This is an 

 indication of recent degeneration. 



Fig. 2. X 7. The left wings of the female imago of Cheimatobia brumata. The wings being far more 

 degenerate than those shown in the last figure, the pattern is much less distinct. 



Figs. ?), 4, 5, & 6 : all x 7. The left wings of four female imagines of Hybernia progemmarta. The 

 individual dift'erences in size, shape, and in the length and character of the fringe are seen to 

 be very marked. The mai'kings, not represented in the figures, were also very different. This 

 great individual difference also points to recent degeneration from a more highly developed 

 condition. 



