130 MOHPHOLOGY, ETC., OF THIS MICKOPTEKYGIDJE, i., 



important to notice that, in the venation of Letn, the fusion of 

 1A with Cu 2 is actually accomplished for a short distance (Text- 

 fig. 14, A;), the hasal piece of Cu 2 being bent transversely so as to 

 look like a cross-vein. The reduction in the length of the fused 

 portion in this family is surely to be expected, when we consider 

 that the anal area has undergone reduction, through the narrow- 

 ing of the base of the wing; the change in the direction of the 

 anal veins from an inclination of about 30° to the longitudinal 

 axis of the wingj in J/icropteryyidte and Prototheorid<e, to more 

 than 45° in Leto and other Hepialidce, and the comparative 

 shortening of 1A, so that it ends up at less than one-fourth of 

 the whole wing-length from the base in these insects, instead of 

 at more than one-third as in Micropterygidce, must surely account 

 for some si it'll t alteration of this kind. 



Ri J^ 



Text-fig. 14. 

 Hindwing of Le/o staceyi Scott; to the left, the pupal tracheation; to the 

 right, imaginal venation, basal part of wing only, k, in botli figures, 

 the point where fusion of veins Cu., and 1A takes place. As the 

 tracheae Cu and 1A were clearly visible in the fresh imaginal wing, 

 they are drawn in situ in the right-hand figure. ( Both figures x 4h). 

 For lettering, see p. 136. 



Though it should be obvious that the presence or absence of a 

 particular cross-vein ought not to be used as an ordinal character 

 — since these structures, not being preceded by tracheae, are 

 exceedingly liable to variation — yet Professor Comstock includes 

 in his ordinal diagnosis for the Trichoptera (inclusive of the 

 Micropterygidce) the presence of the cross-vein between " the 



