248 MB. E. B. POULTON ON THE EXTEENAL 



towards the degeneration of the female sense-organs, because, as the organism becomes 

 more and more sluggish, the necessity for these organs diminishes both for sexual and 

 for other purposes. The reverse takes place in the male, as the sense-organs become 

 specialized for sexual purposes. It is likely that such specialization implies a partial 

 restriction and not an actual limitation of function, the antennae still remaining sense- 

 organs of very general use, although their high development is related to one out of 

 many possible functions. 



It is obvious that the diminution in the activity of one sex must in certain cases 

 involve other organs in addition to the antennae. These will be considered in the next 

 Part, and will be found to throw further light upon the subject of the present Section. 



Part V. — The Pupal Wings. 



1. The Relation of Pupal to Imaginal Wings. — Considering the conclusions already 

 arrived at by the comparison of pupal and imaginal antennae, — that when an imaginal 

 organ falls into disuse and shrinks, the corresponding pupal organ shrinks at a very 

 much slower rate, and so presents a picture of the long-past condition of the former — it 

 became very probable that a similar relation would be found to obtain in other sets of 

 organs, and especially the wings. I have already shown that the function of the wings 

 bears a close relationship to that of the antennas. 



My attention was first called to this comparison between pupal and imaginal wings in 

 species of which the females possess these organs in a very rudimentary form, by the study 

 (in 1885) of the remarkably degenerate female pupae and imagines of Fmnea nitidella. 

 Although the males of this species are active bombyciform moths, the females are ex- 

 ceedingly degenerate, never leaving the case in which the pupa was contained, but 

 sitting upon the end of it for their whole life. In this position they deposit their eggs 

 in the empty pupal shell within the case from which they themselves emerged. Corre- 

 sponding to this sedentary life, the wings are reduced to minute tubercles, so small 

 as readily to escape detection, and having neither the shape nor appearance- of wings. 

 On examining the female pupa I saw at once that it possesses small but distinct wings of 

 characteristic structure and shape, and with the normal relation to the other appendages 

 and to the meso- and metathoracic segments (Plate XXVII. fig. 14). The male pupa 

 is shown in figs. 12 and 13. 



This comparison is exceedingly interesting, for it at once disposes of the view that the 

 rudimentary wings of such females as these are not due to degeneration from a winged 

 condition, but are remnants of truly ancestral, partially developed structures. This 

 view is also rendered equally improbable by other considerations. Thus, it has already 

 been shown, by means of the pupal antennas, that such females formerly resembled the 

 males to a greater extent than at present in one set of rudimentary organs, suggesting 

 that other sets have had a similar history. Furthermore, we must probably look for the 

 origin of wings in some of the suppressed stages which preceded that represented by the 

 pupa, inasmuch as pupa? always possess wings ; and it seems certain that these organs 

 originally arose in the phylogenetic development after the manner which is indicated by 



