PHYLOGENY. 11 



Pyralid subfamily Phycithue and a few other forms the frenulum is 

 single iu both sexes. In the two most generalized families, the 

 Micropteryciidce and Hepialido', the wings are not connected in any 

 way ; the others all have the frenulum developed, or in some groups, 

 such as the Paj^iUones, Arbelida\ Lasiocuinpida;, Bomhycidce, Saturn- 

 iadce, and some genera of families that usually possess it, it, has become 

 aborted and its function is assumed by an expansion of the base of 

 the costa of the hind wing. 



The margins of the wing are termed (1) the fore margin or costa 

 with the apex at its extremity, (!2) the outer margin or termen with 

 the tornus or outer angle at its junction with (3) the inner or dorsal 

 margin ; the termen and the terminal part of inner margin are 

 fringed with elongate scales or cilia. 



Phylogenx of the Lepidopteea. 



During the evolution of more or less specialized forms from the 

 most generalized ones, their ancestors must have passed through 

 certain stages which can be inferred with tolerable exactitude from 

 the study of existiag forms. The present families and genera are 

 not of course derived from other existing ones, but from their 

 ancestors, and when a family or genus is said to be derived from 

 another all that is meant is that, in order to reach their present 

 stage of specialization, their ancestors must have passed through a 

 stage which would in essential points of structure come within the 

 definition of the other family or genus. 



The Lepidoptera are primarily divisible into two groups, the 

 lower consisting of the two generalized families Micropterygidce 

 and Hepialidce, characterized by having 12 veins to the hind wing 

 as in the fore wing, a small lobe at the base of the fore wing — the 

 so-called jugum — which is really the ' alula ' found in many 

 JS'europtera, Hiimenojitera, and Diptera, and by the wings not being 

 articulated together in any way. Of these the more generalized 

 are the Micropterygidcv, very closely related to the Neuropterous 

 TricJioptera or caddis-flies, and distinguished by the great develop- 

 ment of the maxillary palpi and by having tibial spurs, both of 

 which are absent in the Ilqnalidw wlaich are derived from them. 



The other families constitute the Frenatce, with at most eight 

 veins to the hind wing and the wings articulated with one another 

 by a frenulum and retinaculum, or, in forms in which these are 

 aborted, by an expansion of the costa of the hind wing. 



Of the Frenatce the most generalized groups of families have 

 vein 1 (" of the hind wing present and vein 8 free from the base or 

 connected with the cell by a bar, and of these the Tiiwidce and 

 Tortricidce, with at least one medial spur of hind tibiae well 

 developed, come nearest to Micropteryx, from which they are 

 possibly directly developed. 



From the Tiaeidre are derived: — (1) The Sesiadce, with vein 8 of 

 hind wing aborted ; (2) the Orneodldce and Pteropliorido', with the 

 wings divided into plumes ; (o) the Pyralida\ with vein 8 of hind 



