THE EXTERNAL MORPHOLOGY OE THE LEPIDOPTEROUS PUPA. 57 



genetic significance, and when the more generalised species have been 

 thoroughly examined possibly some new light may be thrown on the 

 evolution of the Lepidoptera. That the forms described by Jackson 

 and Poulton comprise the whole of those occurring in Lepidoptera is 

 highly improbable, and Cholodkowsky (Zeitschrift far wiss. Zool., vol. 

 xlii., 1885) states that in Netnotois metallicus, a generalised Adelid, 

 there is only one aperture, viz., the posterior of the two normal ones. 



Some very interesting superficial structures appear to be carried on 

 from the larval to the pupal stage, e.g., the anal prolegs of the larva 

 can sometimes be traced distinctly as convex cushion-like structures 

 on each side of the anus, and, in certain individuals, may even retain 

 the relative size and appearance which are characteristic of the larva. 

 Packard figures (Bombycine Moths of America, p. 74) a pupa of Phassus 

 triangularis with longitudinal flattened tubercles representing vestiges 

 of the anal prolegs. Poulton figures (Trans. Linn. Soc. Lond., 2nd 

 ser., v., pi. xx., figs. 8, 9, 10) the different aspects of such an example 

 in an extreme form of Smerinthus popidi. The four pairs of ventral 

 prolegs, however, only leave functionless traces on the pupal cuticle, 

 and Poulton says that, although ' ' the first and second pairs are hidden 

 beneath the forewings, yet on the latter being raised (in pupre placed 

 in spirit immediately after throwing off the larval skin) the scars can 

 be seen, and they may even be detected in living pupre with exception- 

 ally transparent wings (e.g., Miselia oxgacanthae), the third and fourth 

 pairs of prolegs nearly always leave conspicuous scars upon the 5th 

 and 6th abdominal segments." The same observer further notes 

 that the caudal horn of the Sphingids always leaves a scar on the 

 pupa even in those species (Choerocampa elpenor, &c.) in which it is 

 but feebly developed at the end of the larval stage. It is especially 

 distinct in the pupa of Macroglossa. stellatarum, whilst in that of 

 S. tiliae it is quite smooth, the rest of the pupal surface being corru- 

 gated. The blunt horn of Endromis versicolor also leaves a large scar, 

 very different from the rest of the pupal surface in appearance. In 

 some Sphingid pupas, there is also a well-marked depression on the 8th 

 abdominal segment behind the scar, which appears to be due to the 

 horn becoming horizontal before the last larval ecdysis so that the 

 adjacent larval cuticle is depressed, leaving a permanent impress upon 

 the then soft cuticle of the pupa. Poulton further notes that scars, 

 representing the soft elevations on the 1st and 8th abdominal segments 

 of the larva of Triaena psi, can be plainly detected upon the correspond- 

 ing segments of the pupa ; he also considers that the rough plate upon 

 the dorsal surface of the anal flap of the larva of Smerinthus tiliae is 

 represented by the extremely rough dorsal surface of the terminal spine 

 of the pupa, and that the glabrous corneous black plate occupying the 

 dorsal surface of the anal flap in the larva of Phalera bucephala is repre- 

 sented on the anterior dorsal part of the 10th abdominal segment of the 

 pupa, which forms a deep furrow with the 9th abdominal, the edge of 

 the furrow being crenated. The brightly-coloured hair-bearing warts 

 of the larvre of the Saturniids, also leave hairless scars, which are 

 usually much smoother than the rest of the pupa and somewhat 

 depressed below the general surface. 



Somewhat different from these are the actual hair-tufts, correspond- 

 ing more or less with the tussocks found inthelarv^p of certain Liparid 

 moths. These are distinctly marked on the first three (or four) 



