2 BRITISH LEPIDOPTERA. 



the neuration of the Hepialidae and Cossidae, and remarks that they 

 resemble the Trichoptera no less than the Micropterygidae, though the 

 Hepialidae exhibit other close analogies with the Trichoptera. He 

 also adds that the middle cell of the wing in the Phryganeidae is not 

 fundamentally different from that of the Hepialidae, Cossidae and 

 Micropterygidae, whilst the hind-wings of the Psychidae exhibit similar 

 characters. 



This brief summary indicates the directions in which it has been 

 suggested that the Lepidoptera are allied to the Trichoptera. The 

 nature of the alliance has been variously discussed, but the general 

 conclusions reached fall into one of two lines : — (1) That the Lepi- 

 doptera have descended by way of the Micropterygides, Hepialides, 

 and Psychides directly from the Trichoptera. (2) That the Trich- 

 optera and Lepidoptera have developed from a common ancestor. 



To discuss this matter satisfactorily we must first consider the 

 similarities between Lepidoptera and Trichoptera. The resemblance 

 between their larvae is very strong, their external structure being almost 

 the same, the principal difference being that the lepidopterous larva 

 possesses abdominal prolegs. These, however, are absent in Micropterygid 

 larvae, as well as in other lepidopterous larvae whose habit it is to mine 

 into their food-plants. 



The similarity of the pupa of Micropteryx to that of the Trichoptera 

 has been already noticed. The abdominal segments of both are more 

 or less freely movable upon each other. They form the " Pupae Liber-ae " 

 of Packard, whilst those generalised lepidopterous pupae, which have a 

 considerable number of free (movable) abdominal segments, the "Pupae 

 Incompletae" of Chapman, are much nearer to the ancestral forms 

 than the " Pupae Obtectae," which represent the more specialised forms. 

 The lepidopterous pupa has been looked upon as presenting a sub- 

 imaginal condition of a type midway between the ametabolous and 

 metabolous orders of insects. This has been suggested by the con- 

 dition of the pupal wing-cases, which are similar to those of metabolous 

 nymphs, such as Dermaptera, Terinitidae, Psoeidae and Hemiptera. 

 Spider has shown that the neuration of the lepidopterous pupa is 

 almost identical with that of the Blattidae and Fulgoridae. Packard 

 says that the "wings of the lepidopterous pupa may be said to be in 

 the nymph stage of the ametabolous insects mentioned, since they are 

 direct outgrowths from the tergites of the segments from which they 

 arise." He further says that " if the wing-cases of any lepidopterous 

 pupa, together with the meso- and meta-thorax are, before the larval skin 

 is moulted, removed and spread out," it will be seen that " they bear, 

 as Spider shows, a striking resemblance to those of a beetle, Term.es, 

 Psoais, or any hemipterous insect." He further points out that the 

 pupal neuration, as well as the appendages — maxillae, labium and 

 legs — are ancestral and phylogenetic, showing considerable differences 

 when compared with the corresponding structures in the more 

 specialised imago. 



The importance of the pupa, as bearing on the origin of the Lepi- 

 doptera, is also very evident when the more generalised forms of the 

 lepidopterous pupa are compared with the more generalised forms of 

 the dipterous pupa, as exhibited by the Bibionidae, Tipulidae, etc. 

 Packard asserts that the close resemblance between the orthorhaphous 

 dipterous pupa and Tineid pupa, affords strong evidence that the two 



