60 BKITISH LEPIDOPTEEA. 



irregular hook-like cuticular processes. Further observation would 

 undoubtely prove that such markings as these are of very general 

 occurrence. 



With the external assumption of the pupal stage, there is, as we have 

 noticed (ante p. 10), a cuticular secretion formed by the hypodermic 

 cells, which hardens on exposure to the air and fixes the wings, legs, &c. 

 to the surface of the body. The nature of this fluid has not yet been 

 thoroughly investigated. It has been suggested that it may be analogous 

 with that found in lizards, snakes, &c, where certain cells break down 

 completely and provide a liquid which facilitates the exuviation of the 

 old cuticle. It has also been suggested that the secretion may be regarded 

 as a modified cuticle thrown off with the first formed pupal cuticle. The 

 Ephemerids cast a thin pellicle after escaping from the subimago state, 

 and an imago of Acherontia atropos has been observed to moult a 

 complete and thin pellicle after its emergence from the pupal cuticle 

 (Curtis, Brit. Entomoloyy , desc. pi. cxlvii), whilst some Hymenoptera 

 (Bombus) are known to cast a thin pellicle with the pupal skin, which 

 has been supposed by Packard to be identical with the skin cast by the 

 active subimago of Ephemera soon after it takes its flight. Whatever 

 explanation may be finally given of this phenomenon, it maybe well to 

 remark here that possibly all imagines of Lepidoptera are partly swathed 

 in a transparent almost structureless membrane, in which the wings, 

 legs, &c, are encased until the emergence of the imago, and one must care- 

 fully remove this internal pupal covering (or external imaginal covering) 

 from the limbs of an imago extracted just previous to the point of emer- 

 gence from the pupa, otherwise the imago will fail to develop its wings. 

 We have repeatedly taken a fine pellicle from the wings of Aylais urticae, 

 removed from the pupa (when fully coloured), and find that if this be 

 not done, it is not successful in shedding it, as was the Acherontia 

 atropos noted by Curtis. The fine skin shrinks up on the emergence of 

 the imago and traces of it can generally be found in the cast pupal 

 skins of the large moths, but its attachment suggests that, normally, it 

 must be cast with the pupal envelope and that the difficulty of the 

 emergence of the imago is due to the fact that it must release itself 

 from these swathings rather than any difficulty of freeing itself from 

 the hard pupal shell with which it is never really in contact. The 

 question here suggested, properly followed up, might throw light on the 

 obscure question of the origin of the quiescent pupal stage. Chapman 

 asserts the belief that the delicate skin here described is only the 

 layer of the cuticle that covers the unexposed portions of the organs, 

 only external parts being provided with the typical dense covering, 

 and that it exists for no other parts. We have ourselves only observed 

 it around such organs, and his explanation, therefore, is highly 

 probable. He says that "these delicate films are the coverings of 

 parts that are not superficial, and consequently retain the delicate 

 character of the skin of the pupa, with all parts free. Of course, in 

 some pupa3-incompleta3, some of these inner surfaces (in pupre-obtectre) 

 are more or less exposed, and have dense coverings ; the body, each of 

 the four wings, and each of the appendages, has a pupal skin, and all 

 these have to be shed as well as the outer hardened surface," but he 

 objects entirely to the attempt to interpret these as a second pupal 

 skin. 



We ought, perhaps, to notice'here, the substance that forms the 



