MORPHOLOGY OF THE LBPIHOPTEROUS PUPA. 263 



Fig. 24. X 7. The left pupal wings and adiacent parts ou the dorsal side of Grapta G-album. \\\ the 

 previous figures of pupal and imaginal wings (figs, lfi-23) the general sequence leads from 

 species with a comparatively sim])le and continuous hind margin (figs. 16-19) to those with a 

 more indented hind margin (figs. 20-23). The sequence being fi'om more generalized to 

 more specialized aud recent types, it was found that the mark representing the imaginal hind 

 margin on the pupal wing, when it differs from the hind margin of tlie imago, always varies 

 iu the direction of greater sim])licity. This being the case, I was very anxious to test these 

 results by an examination of the pupal representative of the imaginal hind margin in Grapta, 

 which possesses a far more jagged and indented hind margin in the imago than any other 

 species found in this country. The pupal line is shown at H'.M'., and comparison with the 

 corresponding part of the imago (fig. 25) shows at once that a more ancestral condition of 

 the imago is preserved in the pupal sculpture and marldngs. Fig. 25 shows us a hind margin 

 which is the culmination of specialization in this direction, while the corresponding part of the 

 pupa is not mdely different from the condition met with in the imago of V. poiijrhlorus 

 (fig. 28) or V. lo (fig. 21). The white areas surrounded by pigment on the metathorax and 

 first abdominal segment correspond to two of the golden spots upon the living pupa. 



Fig. 25. Natural size. The outline of the left fore wing of the imago of Grapta C-atbtim, for com- 

 parison with the preceding figure. 



Fig. 2H. X 7. The arrangement of the main tracheal system in the left hind wing of the pupa of Papitio 

 Machaon, as seen from within (viz. corresponding to the underside of the imaginal wing) . 

 Comparison with the imaginal wing shows that, although the venation of the latter corresponds 

 in a general way with the arrangement of the pupal tracheae, the details are widely different. 

 The same facts hold for the fore wing of pupa and imago. We therefore see that the tracheae 

 of the pupal wings do not by any means follow the arrangement mapped out on the pupal 

 cuticle, an arrangement which they will afterwards assume when enclosed in the veins of the 

 wing of the developing imago. 



