176 PROF. W. H. JACKSON ON THE 



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note, p. 173]. 

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DESCRIPTION OF THE PLATES. 

 Plate XV. 



Fig. 1. Pieris brassicce, male. Ventral view of tbe four terminal segments (7, 8, 9, 10) of the abdomen. 

 £ indicates the aperture of the ductus ejaculatorius. The tenth segment bears tbe susteutor 

 ridges, s.r. of Riley. The centre of the segment is marked by a line, tbe anal furrow, which 

 corresponds to the furrow between the two anal prolegs of the caterpillar, and leads to the anus 

 at its posterior end. cr., the cremaster; r.p., the eminences representing the anal prolegs. 

 The natural size is indicated in this and nine of the following figures by a line at the side. 



Fig. 2. P. brassica, female. This figure is a corresponding view to the preceding, and tbe same 

 explanation applies to the letters. ? indicates the two female apertures. 



Fig. 3. P. brassicce, female. A lateral view of the four terminal segments of tbe abdomen. The 

 perfect spiracle of the seventh segment, and the abortive spiracle of the eighth segment, are 

 shown. Tbe letters as before. 



Fig. 4. Vanessa Io, male. J 1 indicates the aperture of the ductus ejaculatorius. A similar view to 

 fig. 1. 



Fig. 5. V. Io, male. Enlarged view of aperture of ductus ejaculatorius. Obj. aa, oc. 2, Zeiss, draw- 

 tube full out. 



Fig. 6. V. Io, female. ? indicates the ventral furrow crossing the eighth and ninth segments in which 

 are situated the two sexual apertures. The latter are minute and not visible. A similar view 

 to fig. 1. 



Fig. 7. V. Io, female. Enlarged view of the ventral furrow of the preceding figure. Obj. aa, oc. 2, 

 Zeiss, draw-tube full out. 



Fig. 8. Papilio Machaon, male. A similar view to fig. 1. J indicates the aperture of the ductus 

 ejaculatorius. s = sustentors. 



