THE EXTERNAL MORPHOLOGY OF THE LEPIDOPTEROUS PUPA. 53 



examination. The sex can very rarely be made out in the lepid- 

 opterous larva without dissection, but, since the external structures 

 which are distinctive of sex in pupas are developed towards the close of 

 larval life, and the cuticle that lines them is in continuity with the 

 cuticle of the future pupa, it is conceivable that the larval cuticle 

 might be sufficiently transparent to permit the external sexual organs 

 to be seen in the adult larva. Distinctive external anatomical indica- 

 tions of sex are, however, altogether wanting in the lepidopterous 

 larva, and the sex is not to be determined save by dissection, except 

 in the few cases, e.g., Ephestia kiihniella, where the integument is of 

 sufficient transparency to permit the testes and ovaries to be seen, and 

 where, at the same time, there is a difference of colour in these organs. 

 Male sexual organs. — With the assumption of the pupal form the 

 external organs are seen to be already formed, and the examination of 

 almost any large male pupa with the naked eye will show on the venter 

 of the abdominal segments, "two convex or flattened, roundish, oval, 

 or trianguloid tubercles, placed one on each side of the middle ventral 

 line, in the 9th abdominal segment. Careful examination throws some 

 doubt upon the certainty of this segmental relationship, but there is no 

 doubt, however, that the organs always occur in the zone of the 9th 

 abdominal, viz., in an area which would be included in the segment, if 

 the boundaries of the latter were produced in the direction indicated by 

 their course in the dorsal and lateral regions. Between the tubercles 

 is a furrow which generally becomes a deep pit in its central part ; this 

 pit is the ancient opening of the pupal vas deferens, and it now corre- 

 sponds externally to the termination of the ducts internally " (Poulton). 

 It is further pointed out that some pup* approach the condition of a 

 perforate orifice, and Poulton states that a favourable pupa of Smerin- 

 thus popidi will show, if examined from the inside, the lips of the 

 depression completely introverted, their internal surface having the 

 black appearance and peculiar roughened texture which is characteristic 

 of the exterior of the pupa, and with which it is, of course, continuous. 

 The surface of the introverted funnel-like opening is covered with the 

 same lustrous white layer which invests the whole interior of the cuticle, 

 and which, therefore, is contrasted very sharply with the internal 

 surface or lumen of the funnel. In this case, the funnel is not closed 

 at its deepest point, the lumen being obstructed a little higher up by 

 the fusion and hardening of the semifluid substance into a solid plug 

 immediately after pupation. When looked at from within, the sides of 

 the sharply truncated funnel are quite free, recalling most vividly the 

 condition in which the lumen was perforate throughout. The whole 

 appearance from within, in fact, singularly resembles that of one of the 

 superficial functional spiracles looked at from the same point of view. 

 These have similar introverted lips, also sharply truncated, and showing 

 the characteristic black surface which lines the lumen. The rudi- 

 mentary 8th abdominal spiracle, on the other hand, is completely closed 

 below, and the white surface lining the pupal cuticle is unbroken over 

 it. It is very remarkable that this most ancestral generative organ 

 sliould, in certain cases, retain such strong indications of the time when 

 it was functional. On the other hand, there are proofs of the ancestral 

 nature of the male organs, and of their rudimentary condition, as far as 

 the pupa itself is concerned. Thus the individual differences are very 

 great in position and form, and in the degree to which the structures are 



