MOEPHOLOGY OF THE LEPIDOPTEROUS PCPA. 249 



the ancestral Ortlioptera — namely, that they arose gradually, as their slowly unfolding- 

 structure rendered possible the transition from the slight prolongation of a jump — their 

 first locomotive function — into the sustained movements of true flight. If these argu- 

 ments be correct, it is clear that fairly-developed wings such as pupse possess are very 

 far from representing the original condition of these organs, while the rudimentary wings 

 of certain imagines are clearly due to degeneration. 



In order to test further the conclusions arrived at by studying F. nitidella, I made 

 use of another very common species of which the females have rudimentary wings, viz. 

 Orgyia mitiqim. After emergence from the pupa the female moths sit on the outside of 

 their cocoons, which they never leave, but deposit their eggs upon the surface of the silk. 

 Although very degenerate, they possess distinct wings of the usual shape, though very 

 small and quite useless. The size and shape of the left fore wdng are shown in 

 Plate XXVII. tig. 11. I then examined the pupal wings and found that, although very 

 much smaller than those of the male, they are considerably larger than the wings of the 

 female moth, as is seen by comjmring figs. 10 & 11, Plate XXVII., both figures being 

 magnified to the same extent. Hence we find precisely the same relation between the 

 wings of the male and female pupa, and between those of the latter and of the female 

 imago, as in Fumea nitidella, although degeneration has gone further in the last-named 

 species. 



Some of the more degenerate FsijcliidcB were then selected for examination. In 

 these the female imago is a mere bag of eggs, and remains permanently enclosed in the 

 pupal shell. In the majority of female pupse examined, the lost imaginal parts — wings, 

 legs, antennte, &c. — are evidently represented by confused creases on the corresponding 

 parts of the cuticle. In one unnamed species, kindly lent me by my friend Mr. W. 

 White, the pupa retained far more distinct traces of structures formerly possessed by the 

 imago. The anterior part of the pupa is represented in fig. 15, Plate XXVII., and it is 

 seen that the wings are distinct as small pouches on the meso- and metathorax, that 

 the legs, antennae, and even the eyes and moutli-parts can be plainly made out. although 

 of a very rudimentary nature. The moth itself appears to be as degenerate as any 

 Psychid in which the traces of lost parts upon the pupa are far more obscure. The 

 figure also shows that the pupal prothorax splits along the median dorsal line and that 

 the hairs of the enclosed imago are seen through the opening, so that the first part of 

 the process of emergence from the pupa appears to be recapitulated in this most 

 degenerate form. 



Purther examination of various species in which the female imagines possess rudi- 

 mentary wings also supported the conclusion that such degeneration is of recent date. 



Thus many species of Geometrce were investigated. The minute functionless wings of 

 a female of Cheimatobia boreata were found to retain distinct traces of the colours and 

 patterns which are characteristic of the functional wings of the male, thus supporting 

 the conclusion that the reduction in size is very recent. The wungs of a female of the 

 closely-allied Cheimatobia hrnmata were found to be much smaller, with far less distinct 

 indications of pattern (compare figs. 1 & 2, Plate XXVII.). The Avings of the female 

 ILybernia progemmaria are less reduced than those of Cheimatobia, although quite useless 



