338 



THE WINGS OF LEPIDOPTERA 



Stem of media is well-preserved ; and in some other families as the Megal- 

 opygid^, Eucleidse, and Pyromorphidse, it is preserved in some members 



of the family and lost in 

 others. The retention of the 

 main stem of media is obvi- 

 ously a character indicating 

 a comparatively generalized 

 condition of those families in 

 which it exists. 



In very many cases where 

 the main stem of media is 

 lost no trace of it remains; 

 but frequently the position 

 formerly occupied by it is 

 indicated by a faint line or 

 scar; such a line exists in 

 the fore wing of Cither onia 

 regalis (Fig. 345). Less fre- 

 quently vestiges of the basal 

 part of media remain as short 

 _ stimips, projecting into cell 



'^ '^f^^ R+M, from the outer end 



ig- 34 • mgs o ac . ^^ ^^.^ ^^^^ _ vestiges of this 



kind are present in the wings of Anosia (Fig. 346 and 347). 



The transfer of the branches of 

 media to adjacent veins. — Con-e- 

 lated with the atrophy of the base of 

 media is the coalescence of its 

 branches with the adjacent veins. 

 It follows from this that the extent 

 to which this coalescence has gone 

 is an indication of the degree of 

 departure of a form from the primi- 

 tive type. Compare, for example, 

 the hind wing of Packardia (Fig. 

 348) with the hind wing of Adoneta 

 (Fig. 349), two genera of the family 

 Eucleidac. In Packardia, where a 

 remnant of the base of media still 

 persists vein Mi is merely connected 

 withthcradial sector by a cross-vein. 

 But in Adoneta, where the base of -' ,j.^^ 



media of the hind wing is lost Fig. 349. — Wings of Adoneta. 



