592 



Color and Pattern and their Uses 



strial space. All scales, excepting some androconia (scent-scales on male 

 butterfl es) (Fig. 777), possess these longitudinal striae, which traverse the scale 

 from base to outer margin and are very sharp, and sepa- 

 rated from one another by equal distances. The striae 

 sometimes curve in at the lower angles of the blade, con- 

 verging toward the origin of the pedicel; in other cases 

 they fade out at these angles. In scales of Anosia 

 plexippus from 33 to 46 striae, averaging .002 mm. apart, 

 are present on each scale. There would thus be 12,500 

 of these striae to the inch. On transparent scales from 

 Morpho sp. the striae were .0015 mm. to .002 mm. apart; 

 on opaque (pigment-bearing) scales from the same spec- 



JT IG . 77 6. Scale imen the striae were from .0007 to .00072 mm. apart, 



of Lycomorpha or a j fa e ra j e o f about 35,000 to the inch. 



Constant, show- Tf . , * r i i i i r 



ing cross-stria;. " we examine a long series of scales brushed off from 

 (Greatly mag- different parts of a wing of moth or butterfly, we can 

 always note a series of gradating forms running from slender 

 hair-like form to typical short, broad, flat scale. The significance of this, 

 when we come to inquire about the origin 

 of scales, is plain. Scales are unusual struc- 

 tures among insects: besides the moths and 

 butterflies, only a few beetles, the mosquitoes, 

 the fish-moths, and a few other scattering insects 

 have them. But all insects have hairs. Hairs 

 are structures common throughout the class. 

 And it is certain that scales are derived or de- 

 veloped from hairs. They are a specialized, a 

 highly modified sort of hair. On the lower, the 

 more generalized moths, the hair-like scales are 

 the more abundant. The wings show a thick 

 intermixing of loose, fluffy hair-scales or scale- 

 hairs with more typical scales irregularly ar- 

 ranged. In the higher Lepidoptera, the spe- 

 cialized sort of hairs, namely the scales, com- 

 pose almost exclusively the wing-covering, and 



these scales are arranged in the specialized FlG ?7? Androconia from 

 uniform shingling manner previously described. wings of male butterflies, a, 

 But even on the wings of a butterfly all the 

 gradations from hair to scale can be found by 

 going from base out to discal area of the wing. 

 These gradation series vary in character in dif- 

 ferent families, as shown in Figs. 778, 779, 780, and 781. In some the 



from wing of Nymphalid 

 butterfly; b, from wing of 

 Pierid butterfly; c, from 

 wing of Lyca-riid butterfly. 

 (All greatly magnified.) 



