41 



referred to says that the outer line, as is obvious enough, is the 

 margin of the pupal wing; the inner one (Poulton's line) is the 

 margin of the imaginal wing. 



'I'his can hardly be the case for several reasons. We talk of 

 imaginal and pupal wings, and the phrases are useful to describe 

 certain things and stages of things ; but we must remember that 

 there is in reality no such thing as a pupal wing, only imagines have 

 wings. What pupae have are not wings, but what are to be imaginal 

 wings, or simply wings ; the word imaginal being in this view of 

 the words tautological and superfluous. 



The wings of pupae are not, then, pupal wings, but imaginal wings 

 at a certain stage of their development. 



This undeveloped imaginal wing is enclosed in a chitinous cover- 

 ing which is pupal strictly, but what it encloses belongs purely to 

 the imago, whether it be inside or outside of Poulton's line. Now, 

 I have stated that all Lepidopterous pupae possess Poulton's line, 

 and if that line be really the margin of the mature wing of the 

 imago, we must conclude that throughout the whole order a strictly 

 imaginal structure exists in the pupae, but is atrophied before the 

 imaginal stage is reached. Now there are imaginal structures in 

 many pupae that have precisely this history, like the expanded 

 antennae of many female moths, or the maxillary palpi of Sesiids 

 and some other Iticompletce. It would not, therefore, be at all 

 improbable for some Lepidoptera to have an imaginal wing appa- 

 rently developed from only the basal portion of the imaginal 

 wing of the pupai, as in fact occurs in apterous females, treated by 

 Professor Poulton in the same paper. 



The difficulty is in the present case that this condition affects the 

 whole order, whilst it is certain that within much smaller limits 

 selection would have reduced the pupal outline to the imaginal 

 limits. 



For the sake of avoiding confusion I have omitted in what I 

 have just said a very important consideration, which makes the state- 

 ments inaccurate, but enables one thing to be considered at a time, 

 and, therefore, may conduce to clearness. The omitted circum- 

 stance is this, that though the mature imaginal organ is apparently 

 wanting or much smaller than it is in the pupal stage, such as it is 

 each part of the pupal organ provides a portion of the imaginal one. 



I believe this to be absolutely true, even in such a case as the 

 maxillary palpi of the Sesiids, where a pupal six-jointed palpus is 

 represented in the imago by an inappreciable stump. Perhaps the 

 most apposite illustration will be found in the pupae of apterous 

 female Lepidoptera, of which Orgyia antiqua is not only a convenient 

 example, but happens to show the necessary details very plainly, 

 and Professor Poulton happens to have figured it in illustration of 

 his paper, though he does not appear to have noticed that the pupa 

 shows Poulton's line very distinctly. The wing of the imago is not 



