636 THE PANORPOID COMPLEX, iii.j. 



It will not be necessary, at this stage, to attempt to prove 

 what is by now universally admitted, viz. that the Suborder 

 Homoneura contains the most archaic existing types of the 

 Order. Also the space at my disposal will not allow of a full 

 review of the characters of the venation, in all families of the 

 huge Suborder Heteroneura. I propose, therefore, to take the 

 families of the Homoneura in order, and study their venation; 

 and then to select only those archaic families of the Heteroneura 

 which will help to elucidate the main problem, together with a 

 few other types which may throw light on important, though 

 subsidiary, problems, such as the origin of the Butterflies. In 

 doing this, it will have to be borne in mind that nianj- of the 

 archetypic characters have already been determined from the 

 evidence in previous Sections, which will be referred to when 

 required . 



Suborder Homoneura. 

 Division Jugo-frenata. 



This division contains only the three families Micropterygidae, 

 Eriucraniidae, and Mnesarchaeidae* As a study of their vena- 

 tion, and its relationships with that of the Trichoptera, would have 

 unduly enlarged this Part, the work has already been done sep- 

 arately (26), and the results are taken for use in this paper. 

 In Text-fig. 76, I have given a diagrammatic representation of 

 the Archetypic venation of the Jugo-frenata, by including in the 

 one figure all the archaic characters to be found in the whole of 

 the genera belonging to this division. The distribution of these 

 characters may be gathered both from my previous paper (26) 

 and, as regards the separate families, from the Table given on 

 p. 650. It is only necessary here to call attention to the charac- 

 ters in which the Jugo-frenata themselves are specialised, — in 

 other words, those characters in which the venation given in Text- 

 fig. 76 differs from that of the Archetype of the Order Lepi- 

 doptera . These are : — 



(1) The far distal position of the forks rf and m/'. This is 

 an important specialisation, frequently present in highly reduced 

 forms, or as the result of stenogenesis . Its presence in the Jugo- 

 frenata is proof that they are of smaller size than the Archetype 

 of the Lepidoptera, which probably came closer to Belmontia 

 in size. 



*I propose to treat these as three distinct families from this Part 

 onwards. 



