KELLOGC;: TAXONOMIC VALUE OF SCALES OF LEPIDOPTERA. 49 



This very regular arrangement of the scales on the wings is not, 

 however, found in all Lepidoptera. Indeed, only among the butter- 

 flies and a few families of moths can a condition even approximating 

 the regularity above described be found. The significance of the 

 arrangement of the scales, and the taxonomic value of different con- 

 ditions of scale arrangement are discussed later. 



This close placing and overlapping of the scales bring it about that 

 the number of scales on a wing is truly prodigious. In Morpho sp., for 

 example, the distance apart of the lines of insertion pits on a bit of the 

 upper wing surface taken from the middle of the forewing is .151 mm. ; 

 the distance apart of the pits in a line is .043 mm. (on the under 

 surface the pits were .05 mm. apart); so that in a space 25 mm. by 

 25 mm., (i sq. in. circa) there would be 165 lines of scales with 600 

 scales in each line, or 99,000 scales to each square inch of wing 

 surface. As the upper and under surfaces of the fore and hindwings 

 combined equal about 15 square inches the total number of scales on 

 the wings of MorpJio may be roughly approximated at 1,500,000. 



The scales are attached to the wings by means of their short 

 pedicels fitting into minute pouches or cups on the surface of the 

 wing membrane. These minute pockets or cups are in general sub- 

 conical in shape, and vary somewhat in length (or depth) in different 

 species. In Microptcryx uiuinaciilclla they average about .008 mm. 

 in length; in Pieris protodicc .013 mm. in length; in Morpho sp. 

 .016 mm.; in Castnia ?.^. (about the size of Vanessa afitiopa) .026 

 mm.; these being the largest cups I have observed. In Erchits strix, 

 one of the largest moths, if not the largest one, the cups average 

 .015 mm. in length. 



The cups sink but slightly, in the more specialized cases of scale- 

 covering, into the wing-membrane, the outer open end being, of 

 course, at the surface of the membrane, and the inner closed end or 

 bottom of the pocket being only slightly below the surface, so that 

 the scale does not stand out from the wing-surface at a considerable 

 angle but lies closely against it. In fact, rather than being sunken into 

 the membrane, the cups rise above the ^^ 

 surface as shown in figure 5, a cross-section 

 of part of the forewing of Parnassius Fig. .5. 



. , , rr-i ^1 i. 1 Diagriim of a cross-section of 



smintheus. Thus the cups are more truly apart of the wing of Parnassius 

 ,. ,, 1 ^ ,1 e £ ,1 • .1 smintheus, showing insertion 



little pockets on the surface of the wing, than cups, 

 pits or cavities in it. 



The cups vary slightly in shape, also, from simple, obtusely- 

 pointed, inverted cones (the apex being the bottom of the cavity) as 

 shown in Eudamus tityrus, to goblet-shaped cavities, bowl outwards, 

 as in Pieris protodice. In Erebus strix the cup is contracted at the 



