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melanic scales that runs along the leading edge of the hindwing from 
the wing base to the outer margin. The most unique aspect of the sex 
brand in N. iole is that it is frequently devoid of scales (Table 1, 
Figure 1C). This condition is not a result of wear as it occurs in 
many newly-emerged lab-reared males (Table 2). When scales are 
present in the sex brand (Figure ID) they may cover up to 100% of 
the brand and vary in form from a scale that is tan, flat, and similar 
to other scales on the wing to one that is black, shrivelled, and 
contorted (Figure 2A-C; Table 2). Within an individual male the 
form of the sex brand scales and the extent to which they cover each 
sex brand is usually uniform. 
Scale attachments in the sex brand differ from those on other 
areas of the wing in appearance and in density. Unlike those in 
other areas, a typical sex brand scale attachment has fewer ridges 
running up its side, is more rounded, and has a pronounced swelling 
or bulge immediately behind the opening of the attachment (com- 
pare Figure 2C and D). This bulge is distinctly collapsed in air dried 
specimens compared with those that are critical point dried. The 
density of scale attachments in the sex brand is almost twice that of 
scale attachments in the immediately adjacent discal cell of the wing 
(Table 3; t = 40.4, p < 0.001; df = 7). 
Examination of descaled wings or wings whose scales had been 
cleared in a dilute solution of sodium hypochlorite reveals that the 
color of the sex brand in live males is due to an orange pigment in 
the integument of the wing. This orange pigment typically extends 
little if at all beyond the edges of the sex brand. The pigment is 
visible under the light microscope in the space between the dorsal 
and ventral surfaces of wings that were crudely sectioned with a 
razor blade. Scanning electron microscopy of these same prepara- 
tions reveals an ill-defined matrix of material, probably pigment, in 
this space that is restricted to the sex brand (Figures 2E and F). 
As pointed out by Clench (1976) the orange color changes to pale 
yellow after the death of the butterfly. The complete transition takes 
about 6 weeks (Table 1) and does not occur at a uniform rate 
throughout the sex brand. Splotches of orange pigment remain in 
some areas while others have changed to yellow (“mottled”). We 
also made the unexpected observation that sex brand color changes 
with male age (Table 1). All newly-emerged, lab-reared males (n = 
52) have dark orange sex brands while older males, as evidenced by 
wing condition, have significantly higher frequencies of mottled and 
yellow sex brands (Table 1). 
