320 



THE WINGS OF LEPIDOPTERA 



Fig. 329. — Scales of Eudea cippus (After 

 Kellogg, '94). 



upon the body, to the short and broad scale, which is best seen upon the 

 wings (Fig. 329). This fact was pointed out by Reaumur nearly two hun- 

 dred years ago (Memoires V. I. 1734); and in more recent times the 



morphological identity of 

 setae and scales has been 

 established by studies of 

 their development. This 

 identity was inferred by 

 Semper ('57) and Landois 

 ('71). Schaffer ('89) point- 

 ed out that both scales and 

 hairs are evaginations of 

 greatly enlarged hypoder- 

 mal cells and figured one 

 stage in the development 

 of the scales. Mayer ('96) 

 gave a complete account of 

 the development of scales and illustrated his paper by most excellent 

 figures of all stages of this development. 



The structure of scales is what would be expected from the fact that 

 they are modified setae, the scales, like setae, being hollow; and the manner 

 of their attachment to the cuticula of the body and its 

 appendages is the same as that of the setae, each scale being 

 provided with a pedicel which fits into a cup-like socket in 

 the cuticula. 



A striking feature of the scales of Lepidoptera is the mark- 

 ings that exist on their exposed surface. These may consist 

 merely of many, very fine, longitudinal ridges (Fig. 329); 

 or there may be series of transverse ridges between the longi- 

 tudinal ones (Fig. 330). 



A cross section of certain scales indicates that the ridges 

 are produced by foldings of the outer wall {i. e. the wall of the 

 scale that is exposed when the scale is in place on the wing). 

 Figure 331 represents cross sections of a scale illustrating 

 this condition. In some scales, however, the lumen of the 

 scale has been filled to a considerable extent by chitin, and 

 the origin of the ridges is not so obvious. Fi^'. 3^0. -Scale 



The scales of the Lepidoptera were probably developed of Lycomorpha 

 from that type of setae known as clothing hairs, and were Kellogg) 

 primarily merely protective in function. This is doubtless 

 their chief, if not only, function on most parts of the body, where they form 

 a very perfect armor. 



