5 9 2 
Color and Pattern and their Uses 
strial space. All scales, excepting some androconia (scent-scales on male 
butterflies) (Fig. 777), possess these longitudinal striae, which traverse the scale 
4jl from base to outer margin and are very sharp, and sepa- 
JB1 rated from one another by equal distances. The striae 
jjjjjl sometimes curve in at the lower angles of the blade, con- 
|||j|l verging toward the origin of the pedicel; in other cases 
■f||f| they fade out at these angles. In scales of Anosia 
plexippus from 33 to 46 striae, averaging .002 mm. apart, 
111 are present on each scale. There would thus be 12,500 
IJjjjf of these striae to the inch. On transparent scales from 
IjJf Morpho sp. the striae were .0015 mm. to .002 mm. apart; 
on opaque (pigment-bearing) scales from the same spec¬ 
ie. 776.—Scale imen the striae were from .0007 to .00072 mm. apart, 
of Lycomorpha or a t the rate of about 35,000 to the inch. 
constans, show- Tr . . r , , , , r . . 
ing cross-striae. If we examine a long series ot scales brushed on 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 
uniform shingling manner previously described. 
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 
P 
§ 
Fig. 777. Androconia front 
wings of male butterflies, a, 
from wing of Nymphalid 
butterfly; b, from wing of 
Pierid butterfly; c, from 
wing of Lycaenid butterfly. 
(All greatly magnified.) 
