206 MR. E. B. POULTON ON THE EXTERNAL 



Fig. 26. The Terminal Abdominal Segments of the Pupa of Sesia fuciformis. 



Fig. 26. x 145. The last two segments of a male pupa, seen from the ventral aspect. The object of 

 the figure is to show the remarkable distortion of the male organs in the individual represented. 

 This is not accompanied by any want of symmetry in the adjacent parts. The anus (A), the 

 large rostrum, the form of the segments, except in the parts directly affected by their close 

 proximity to the male organs, are all undistorted. 



Figs. 27-32. The Terminal Abdominal Segments of the Pupa of Cossus ligniperda. 



Fig. 27. x 7. The last three segments of a female pupa, seen from below, behind, and the left side. 

 The reproductive organs were especially distinct in the individual figured. On the eighth 

 abdominal the rudimentary spiracle and part of the dorsal semicircle of hooks are seen, together 

 with the opening into the bursa copulatrix, which consists of a main aperture close to the pos- 

 terior boundary of the segment and a narrow slit-like forward extension which reaches the 

 anterior boundary. The semicircle of hooks on the ninth abdominal is also seen, together 

 with the distinct opening into the oviducts, normally placed at the apex of the median prolon- 

 gation of the tenth abdominal. On the tenth abdominal the anus is seen at A ; the segment 

 is divided, as in other pupae, into a ventral (x) and a dorsal (x') part. The semicircle of hooks 

 on other adjacent abdominal segments is imperfectly represented on the tenth abdominal. In 

 the median ventral line between the anus and the anterior prolongation there is a mark like 

 that in a corresponding position on the female pupa of Acherontia atropos (fig. 16). In both 

 pupae the mark is due to wrinkles in the pupa-case, and is probably of no morphological 

 significance. 



Fig. 28. x 50. The median ventral area of the eighth, ninth, and part of the median prolongation from 

 the tenth abdominal segments of the same pupa, as seen from within, from the right side and 

 above. The main opening of the bursa copulatrix is seen to be prolonged into a laterally com- 

 pressed funnel-shaped invagination of the cuticle, while the anterior extension is also distinctly 

 marked by a long narrow ridge on the inner surface of the eighth abdominal. The opening of 

 the oviducts is also marked by a very distinct invagination continuous posteriorly with the 

 ridge-like boundaries of the median prolongation of the tenth abdominal. The small hemi- 

 spherical elevation immediately in front of the last-named invagination is probably an indi- 

 vidual variation. 



Fig. 29. x 9. The median ventral area of the eighth, ninth, and tenth segments of the same pupa, as 

 seen from the ventral aspect. Many of the appearances described in fig. 27 can be followed 

 more accurately and in greater detail. The surface sculpture is carefully figured. The above- 

 described mark in front of the anus (A) is clearly shown, together with a pit in the posterior 

 part of the seventh abdominal. The latter structure is probably also devoid of morphological 

 significance. 



Fig. 30. x4. The last two segments of a male pupa, seen from below and behind. The anus (A) is 

 distinctly seen as a vertical slit in the ventral part of the small tenth abdominal. The spines 

 which represent the semicircle of hooks ou other adjacent abdominal segments are far less 

 numerous than in the same part of the pupa shown in fig. 27, but, as in the latter, a single 

 spine placed on each side of the anus is especially strong. The external reproductive organ is 

 distinctly seen on the ninth abdominal ; the lateral tubercles are flattened. Anterior to the 

 organ there is a small flattened area with a different appearance from the rest of the surface. 

 The semicircle of hooks on the ninth abdominal is seen, except in its dorsal part, which in this 

 position is concealed by the tenth abdominal. 



Fig. 31. x 2. The last three segments of the same pupa, as seen from behind. The semicircles of hooks 



