330 



LEPIDOPTERA 



CHAP. 



trachea, and also a " wing-rib " and blood-cells. He remarks that 

 even in nervures, perfectly formed as to their chitinous parts, 

 either wing-rib or trachea or both may be absent. 1 Schaffer 2 

 was unable to find any tracheae in the completed wings he 

 examined, and he states that the 

 matrix of the tracheae and even 

 their inner linings disappear. The 

 wing-ribs were, however, found by 

 him to be present (Fig. 170, A 

 and B). 



The scales that form so con- 

 spicuous a feature in Lepidoptera 

 exist in surprising profusion, and 



B 



FIG. 170. Structure of wing of imago. A, 

 Transverse section of basal portion of wing 

 [of Vanessa ?] containing a nervure : <; 

 cuticle ; ft; wing-rib ; //, wall of nervure 

 (" Grunilmembran ") ; //, hypodermis ; p, 

 connecting columns : r, lumen of nervure ; B, 

 section of a rib ; b, one of the chitinous pro- 

 jections ; sir, central rod. (After Schafl'er.) 



Fiu. 171. Scales of male Lepidoptera. 

 A, Scale from upper surface of 

 Eccres /<niii//t/"x ; B, from upper 

 surface of Pieris m/Hic : C, from 

 inner side of fold of inner margin 

 of hind wing of Laertias phihnor ; 

 D, one of the cover-scales from the 

 costal androconinm of Eudamiis 

 jirofeus ; E, F, G, scales from andro- 

 coniunt of Thorybes pylades. (After 

 Scudder). 



are of the most varied forms. They may be briefly described 

 as delicate, chitinous bags ; in the completed state these bags 

 are flattened, so as to bring the sides quite, or very nearly, 

 together. Their colour is due to contained pigments, or to stria- 

 tion of the exposed surface of the scale ; the latter condition 

 1 ZdtKclir. n-iss. Zwl . liii. 1892, p. 623. 2 Zool. Jahrl. Annt. iii. 1889, p. (346. 



