MORPHOLOGY OF THE LEPIDOPTERA. 145 



which the two typical linear depressions seen in Pieris are effectually obscured. 

 PL XV. fig. 15 is a view of the inner aspect of the empty pupal cuticle of V. Io, and 

 shows the remnants of the chitinous linings of the duct of the bursa copulatrix (b) and of 

 the oviduct (o) respectively, at a late stage, however, of growth, and therefore of greater 

 extent than in the newly formed pupa. Still they indicate the existence of the structures 

 evidenced outwardly in Pieris, and described in V. Io in the second section of this 

 paper (pp. 159-1G0, 162, 164) *. 



(3) In all specimens of Papilio Macliaon that I have seen the ninth somite is very 

 narrow ventrally and is crossed by a line as in Vanessa. The ventral portion of the 

 eighth somite is broader, and a line extends forwards from its hind margin for about 

 one third of its breadth. This type is figured PL XV. fig. 9. 



(4) All the Heterocera which I have examined are characterized by a peculiarity of 

 the ninth sternal region. It is prolonged forwards to a greater or less extent as a 

 triangular plate invading the eighth sternal region, and it is at the same time not clearly 

 limited from the tenth somite behind; or in other words the intersegmental line between 

 the ninth and tenth somites is not quite continuous from side to side across the ventral 

 line. These features are shown in two of the Sphingidse, Protoparce mauritii (Butler), 

 PL XV. fig. 10, and Sphinx ligustri, fig. 12, on the same Plate. The figures also 

 illustrate a further peculiarity of the Heterocera. In Protoparce mauritii it will be 

 noticed that there are two fine longitudinal lines or depressions, one in the eighth 

 sternum and a second, the shorter of the two, at the apex of the triangular forward 

 extension of the ninth sternum, whereas in Sphinx ligustri there is but a single linear 

 depression situated in the sternal region of the eighth somite, inclosed, however, by 

 triangular lines passing backwards. The single depression represents the two depres- 

 sions seen in Protoparce. Of the correctness of this conclusion I have no doubt, for the 

 following reasons : — First, dissection of a one day's old pupa of Sphinx ligustri has shown 

 me the existence of exactly the same parts that are seen in PL XVII. fig. 34, taken 

 from V. Io. There is an anterior vesicle with rudiments of a bursa copulatrix and 

 receptaculum seminis, and a posterior double vesicle. The main difference in these 

 organs, as compared with the organs of V. Io, is that the anterior and posterior vesicles 

 are closely apposed to one another. The second reason is that in the cast pupal cuticle 

 of the same moth, as well as of a Smerinthns ocellatus, I have found two bands united 

 at their bases, which are evidently the cast chitinoid linings of the ducts of the bursa 

 copulatrix (b) and of the oviducal tube (o). They are identical with the structures 

 figured in V. Io on PL XV. fig. 15, and they are shown in figs. 16 and 17 on the same 

 Plate. There is yet a third reason, and that is the occurrence of a single or of a double 

 depression in different chrysalids of the same or allied species. Such a variation I have 

 seen only once, and that quite recently, among the very many examples, probably 200 

 or more, of Sphinx ligustri that have passed under my notice. It is figured PL XV. 

 fig. 13. A specimen of Smerinthns oculatus belonging to my friend Mr. Poulton is a 

 second instance to the point ; as a rule, however, this species has but a single depression. 



See p. 155, on pupre of V. Io of undetermined sex. 



23* 



