54 BEITISH LEPIDOPTERA. 



developed. Furthermore, these organs are often asymmetrical when all 

 other parts of the pupa are entirely normal. The asymmetry may be 

 slight, or pronounced, or accompanied by marked deformity. With 

 regard to the uncertainty as to whether the male organs are on the 9th 

 abdominal segment, the same observer remarks that although they 

 appear to the naked eye to belong to this segment, yet, when consider- 

 ably magnified and well- illuminated, they appear to be surrounded by a 

 furrow which is continuous on either side with the boundary between 

 the 9th and 10th abdominal segments. In some highly magnified 

 figures they appear to belong to an anterior median extension of the 

 10th abdominal. 



Jackson, who refers the male organs without question to the 9th 

 abdominal segment, writes: " The male sex is indicated by a linear 

 depression in the sternal region of the 9th somite, a depression which 

 represents the aperture of the ductus ejaculatorius of the imago. It 

 presents itself in one of three slightly differing shapes — (1) A fine line 

 situated in a raised area and provided with two oval lips, one right, the 

 other left — Pieris. (2) A more strongly marked line enclosed in a 

 nearly circular cup-shaped area, with edges strongly raised. (In some 

 specimens the edges of the enclosing area are more strongly pronounced 

 on the right and left, forming two lips, the area having a more oblong 

 aspect.) — Aglais urticae, Vanessa io, Pyrameis atalanta, Eugonia x>°ly- 

 chloros. (3) A very well-defined linear depression guarded by two lips, 

 one right, the other left. These lips are tumid, broad at their centres, 

 and pointed at either extremity, or, in other words, they are oval or 

 somewhat triangular, the bases of the triangles being the linear depres- 

 sion itself ; the whole structure situated either in the centre of the 

 segment or at its posterior limit — Pajriliomachaon, Sphinx ligustri, and 

 all Heterocera examined." 



Female sexual organs. — The examination of any large female pupa, 

 shows an anterior median extension of the 10th into the 9th (and some- 

 times into the 8th) abdominal segment. Lyonet figured (pi. xxiv., 

 fig. 12) this in Macrothylacia rubi, but it is conspicuous in many (most) 

 Heterocerous pupa?, less so in those of the Ehopalocera. When the 

 10th abdominal extends forwards so far as to impinge on the region of 

 the 8th, the 9th also is prolonged into the latter for a variable 

 distance, thus allowing the female generative organs, really on 

 the 10th, to extend beyond the normal zone of the 9th, abdo- 

 minal. Considerable variation in this extension occurs, even in 

 different individuals of the same species, and Poulton notes that the 

 base of the prolongation appears to be separated from the rest of the 

 10th abdominal in Cossus and Zeuzera, and that there is a median line 

 traversing the prolongation of the 10th abdominal in Macroglossa 

 stellataruw. He supposes, from the constancy and distinctness of the 

 median prolongation and the relation of its apex to one of the genera- 

 tive apertures, that it has some morphological significance, and suggests 

 that " it may represent an ancestral ovipositor, formed as an anterior 

 ventral extension of the 10th abdominal, and now fused to the pupa 

 in its position of rest." He adds that " just as the male intromittent 

 organ seems to be now only represented by the cuticle of that part of 

 it which appeared on the surface when it was withdrawn, so the 

 ancestral ovipositor is only represented by its external cuticular layer." 

 He further considers that this "hypothesis also explains the fact that 



