CHAPTER XXIII 

 THE WINGS OF THE LEPIDOPTERA 



(a) THE MORE GENERAL FEATURES OF THE WIXGS OF THE LEPIDOPTERA 



In the Lepidoptera the wings are membranous and are covered with 

 overlapping scales. They are usually broadly expanded; but in some of 

 smaller forms they are long and narrow. When at rest, the wings are 

 variously disposed in the different members of the order. In a few species 

 the males are wingless. 



The wing-venation is comparatively simple ; the only puzzling features 

 are due either to the coalescence of veins or to the atrophy of veins. If we 

 except the humeral veins, which are described later, in no family is there 

 normally a specialization of the venation by the development of either 

 accessory or intercalary veins; and only the principal cross-veins are 

 present. 



The most striking departure from the hypothetical primiti\'e type is the 

 fact that media is only three-branched. In this respect this order agrees 

 with the Diptera; but the Lepidoptera differs from the Diptera in its 

 characteristic method of coalescence of veins. In this order the coalescence 

 of veins almost invariably procedes outward ; while in the Diptera it often 

 procedes from the margin of the wing towards the base of the wing. 



(b) THE CLOTHING OF THE WINGS OF THE LEPIDOPTERA 



The clothing of scales. — The most distinctive feature of the wings of 

 the Lepidoptera is the coating of scales with which they are covered. This 

 coating of scales is the dust that comes off 

 upon one's fingers when a moth or butterfly 

 is handled. 



When this dust is examined with a micro- 

 scope it is found to be composed of very 

 minute scales of various forms but regular in 

 outline ; and when a wing is looked at in the 

 same way, the scales are seen to be arranged 

 with more or less regularity upon it (Fig. 

 328). Thebody, the legs, and other append- 

 ages are also covered with scales. ' 



It is well-known that these scales are Fig. 328 —Part of a wing of a 



butterfly greatlv magnihed. 

 merely modified setcC. That is, they are 



setae which, instead of growing long and slender as setae usually do, 



grow very wide as compared with their length. Every gradation in form 



can be found from that of the ordinary seta, which occurs most abundantly 



(319) 



