BRITISH LEPIDOPTERA. 



portant statements on the probable origin of the Lepidoptera. He 

 considers that the history of the evolution of the lepidopterous pupa 

 has been largely an attempt to solve the question as to how to escape 

 from the pupa without the aid of imaginal jaws. Without going into 

 the question of how the quiescent pupa of bees or beetles was derived 

 from the active larva-like pupa (if the term, indeed, is at all applicable), 

 such as those of bugs and crickets, he shows that " the great mass of 

 Coleoptera and Hymenoptera have a pupa of very uniform type, help- 

 less from its quiescence, and hence resorting for protection to some 

 cocoon or other cavity ; " these pupae have (as a rule) a very delicate 

 cutaneous structure, and possess no hard chitinous parts. There are 

 many exceptions in these two orders in which the pupa is exposed, 

 and consequently of harder external texture. 



So far, then, there is considerable similarity in the needs of 

 many of the pupaa of Lepidoptera, Coleoptera and Hymenoptera, and 

 the necessity of special modification to allow the imagines in all to 

 escape from the cocoon is evident. In the Hymenoptera and Coleop- 

 tera this is effected by the imaginal jaws, for the imago becomes per- 

 fect within the cocoon, and it not only throws off the pupal skin 

 within the cocoon, but remains there till its appendages have become 

 fully expanded, and more or less completely hardened. In some 

 instances the Cynipidae the jaws are required for no other purpose. 



Chapman states that one or two of the Neuropterid families appear, 

 in this particular, to have followed out precisely the same lines as the 

 Coleoptera and Hymenoptera, whilst others, having developed a quies- 

 cent pupa of delicate structure, have retained well-developed mandibles, 

 by means of which the pupa escapes from the cocoon immediately 

 previous to the emergence of the imago. This peculiar structure 

 associates, of course, the Neuropterous insects possessing it, the 

 Phryyancidac, and the MICROPTERYGIDES. Although the connection 

 between the two latter is evident, yet Chapman points out that there 

 are objections to Sharp's proposal to class the Micropterygids with the 

 Phryganeids, the most important of which is, that the former have 

 lost the imaginal jaws, and possess a distinctly lepidopterous haus- 

 tellum. The phytophagous habit, too, although strong in the 

 Phryganeids, is absolute in the Micropterygids, so that the affinities of 

 the latter are rather with the Lepidoptera than the Trichoptera. 



The Coleoptera and Hymenoptera, however, as a rule, require 

 imaginal jaws for the purpose of obtaining food. This is not so in the 

 Lepidoptera, nor in the other highly specialised order, the Diptera. 

 Having no special use for imaginal jaws, these orders have not 

 retained them simply to escape from the cocoon, but have met the 

 difficulty of escape from the cocoon, without the aid of imaginal jaws, 

 by various modifications. Up to a point their solutions were very 

 similar, although in the most specialised Diptera one or two remark- 

 able advances have been made', of which there is no trace in the 

 Lepidoptera. Taken as a whole, then, there is much similarity 

 between the lepidopterous and dipterous pupre. Chapman states that 

 he sees every reason to believe that the Diptera also originated from a 

 Neuropterous base with the Lepidoptera. 



As throwing further light on the affinities which exist between the 

 Lepidoptera and Trichoptera, Kellogg records that the mode of tying 

 * Trans. Ent. Soc. Land., 1896, pp. 5(57-509! 



