f^^ AND ^^^^ 



JOURNAL OF VARIATION. 



No. 2. Vol. V. February 15th, 1894. 



I'fiE EVOLlJ'flOJM OF tjiE LEPIDOPl'EI^Ol/^ T\JFJ1. 



A SKETCH. 

 By T. a. chapman, M.D., F.E.S. 



The earliest insects did not possess a j^iipa proper. It may be 

 doubted whether the term can be rightfully applied to any stage 

 of some of the Orthoptera, or even of some Hemiptera and Neurop- 

 TERA, the transition from larva to imago being gradual, and extending 

 over several moults, and the habits of the insects differing little in the 

 larval condition from what they are in the imaginal. As the imago 

 came to differ in form and habits from the larva, so there appeared to 

 arise a necessity for a quiescent intermediate stage, which became more 

 and more pronounced as the difference became greater, the change 

 })r(»I)ahly taking place along several different lines of evolution. 



As we are concerned only with the Lepidoptera, it is not necessary 

 to allude to the illustrations of this furnished by other orders, nor to 

 refer to the systems of classification which may be and have been founded 

 upon this circumstance, and which agree with and confirm those based 

 on other and wider considerations. It would follow, hoAvever, from 

 the broad consideration of all orders of insects, that those which possess 

 the most quiescent pupje have lieen the most recently evolved, and in 

 that sense, are the highest. 



When we come to the Lepidoptera, and, applying this principle, 

 look for the species or family which has the least inactive pupa, we find 

 it in Micropferyx, which has been by common consent, im other grounds, 

 regarded as a ver}- low, if not the lowest, lepidopterous type, and pre- 

 sents strong ]ioints of affinity with the Trichoptera. In it the segments 

 of the pupa are distinct, and preserve a certain amount of independent 

 movement, all the appendages (palpi, legs, wings, itc), are se])arateand 

 distinct from each other, and the whole pupa is rather soft. 



When W(i go to the other extreme, to seek the most inat-tive pupa, we 

 fiiul, in eaclj family of tlie Butterfiies, pupre possessing no movement 

 whatever, and which consist of a smootli, rounded, hard case, witli the 

 several segments and appendages represented only by obscure lines on 

 the surface. A few species, classed amongst tlie Tineina, appear to 

 have reached a similar point by an independent route. 



Looking for intermediate stages l)etween these two extremes, we 

 find many of them represented, not perhaps always, nor even often, 



