648 EXTERNAL ANATOMY OF INSECTS. 



others an equilateral one; lastly, some are lanceolate and 

 others linear; again, some have a very short pedicle and 

 others a very long one : with regard to their extremity; 

 some are intire, without projecting points or incisions, 

 while others are furnished with them : of these some ter- 

 minate in a single long mucro, others have several shorter 

 ones ; some are armed with teeth, varying in number 

 from two to thirteen in different species a . Many other 

 forms might be enumerated, but these are sufficient to 

 give you a general notion of the infinite variety of this 

 part of the works of the Creator. I must next say a 

 word or two upon their arrangement on the wing. In 

 most instances this is in transverse lines, which some- 

 times vary a little from a rectilinear course, and the ex- 

 tremity of the scales of one row reposes on the base of 

 those of the succeeding one, so that in this respect their 

 arrangement is like that of tiles in a roof: in some cases 

 it is not so regular: thus the minute scales on the 

 wings of Pamassius Apollo, and others with subdiapha- 

 nous wings, are arranged without order ; in Pieris and 

 other Diurnal Lepidoptera, and many of the Crepuscu- 

 lar and Nocturnal, there appears to be a double layer of 

 scales on both sides of the wing ; the under layer usually 

 consisting of white ones. If you denude the wings of any 

 butterfly, which you may easily do by scraping it lightly 

 on both sides with a penknife, you will be amused to 

 trace the lines in which the scales were planted, consist- 

 ing of innumerable minute dots : the lines of the under 

 side, in some cases, so cut those of the upper side, as by 



a De Geer has given 34 figures of different scales (i. t. vd.f. 28); and 

 in Plate XXII. Fig. 6. a— w. 22 others, collected from Reaumur, 

 are given. 



