MOEPIIOLOGT OF THE LEPIDOPTEROUS PUPA. 



193 



dorsal part of the tenth abdominal of the pupa, which forms a deep furrow with the 

 ninth abdominal. The edge of the furrow is crenated (see Plate XXI. fig. 6). 



4. Larval tufts of Hairs indicated on the Pupa. — In the larva of Orgyia pudibunda 

 there is a well-known tuft of hairs, the " tussock," upon each of the first four abdominal 

 segments, and these are distinctly marked on the first three abdominal segments of the 

 pupa, and perhaps to a slight extent on the fourth. On the other hand, there is a long 

 pencil of hairs on the eighth abdominal segment of the larva, of which I could detect no 

 trace in the pupa. 



The larva of Orgyia antiqua also possesses four large tufts in the position described 

 above, and the indication of these structures upon the first three abdominal segments 

 is perhaps the most conspicuous feature of the pupa ; but there is not the slightest 

 trace of the fourth tuft. The three tufts in the pupa form squarish light-coloured 

 patches, which are very distinct against the dark pupal cuticle, and are especially promi- 

 nent and well defined in male pupte, which are much blacker than females. The 

 entire absence of any trace of the fourth tuft is very remarkable. 



These appearances on the puptie belong to a very different category from tlie merely 

 mechanical scars, such as those produced by the caudal horn in Sphingidae &c. and by 



Fig . 2. 



Jig .1 



the four anterior claspers ; for in the former case the pupa does not bear a scar of the 

 larval tuft, but possesses a true hairy tuft itself. On the other hand, hairy prominences 

 may be represented by mere scars, as in Acronycta psi (see woodcut 1). 



Furthermore, in the pupa of Saturnia carpini distinct scars may be found which have 

 been left by many of the brightly coloured hair-bearing warts of the larva. Tiie scars 

 are quite hairless and are much smoother than the rest of the pupa ; they are rather 

 depressed below the general surface. 



5. Larval Markings upon the Pupa. — Sometimes the characteristic markings of the 

 larva may be seen upon the pupa immediately after the skin of the former is thrown off, 

 and these appearances may be fixed by placing the pupa in spirit and thus checking the 

 darkening of the surface. The persistence of such colours depends upon the fact that 

 the hypodermis cells of larva and pupa are the same ; so that any pigment contained in 

 them during larval life may remain unchanged after the pupal period has begun. 

 Such colours are, of course, concealed in the living pupa by the opaque cuticle. I first 

 noticed the persistence of larval colours in the freshly formed pupa of Sphinx 



