MEMBRANACEOUS WINGS. 277 



fishes are covered. These scales, upon which the beauty of 

 lepidopterous insects so entirely depends, are easily detached 

 in the form of a fine dust, which, when examined with the 



microscope, are exceedingly variable in their form, but gene- 

 rally more or less wedge-shaped, or oval ; sometimes toothed, 

 or notched, at the broadest end, some having a slender foot- 

 stalk. The membranous surface of the wing itself exhibits 

 the appearance, when similarly examined, of numerous 

 minute impressions arranged in lines, in which the base of 

 the scales are planted, being laid upon each other like the 

 tiles on the roof of a house. The derivation of the name of 

 the order, Lepidoptera (scaly wings), expresses this character. 

 It has been suggested, that the form of these scales might be 

 serviceably employed in furnishing specific characters, for 

 the determination of the various species of lepidopterous 

 insects ; but this is quite impossible, since scales of every 

 possible form are found upon a single individual, as may be 

 seen from the preceding figures, all of which represent scales 

 from the goat-moth. 



Here it will be serviceable to notice a few of the more cha- 

 racteristic variations which occur in the markings of the 

 wings of lepidopterous insects (see fig. 134) ; these are, 



