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§ XI. The Scent-scales of the Male of Dione vanillae . 1 
Plate H, Figs. 8-9. 
Dione vanillae leads, I might say compels, me to recur to the scent- 
scales of the Maracuja butterflies, because their shape and arrangement in 
this insect differs so greatly from that of most of its allies. 
Although in some years the commonest of the Maracuja butterflies, 
Dione vanillae has been so scarce this year that I have only recently, at 
the approach of winter, received the first male. When I looked for scent- 
scales in the usual place, on that part of the hind-wing which is covered 
by the fore-wing, I could find no trace of them ; but the peculiar appear¬ 
ance of the nervures of the fore-wing showed me at once where to search. 
The first six veins of this wing (adopting Herrich-Schaeffer’s notation ; 
therefore the inner marginal [submedian] vein and the branches of the 
median and discoidal [radial]) appear on the foxy-red ground colour as broad, 
inflated black streaks, and further examination shows that these streaks 
are composed of a row of dilatations running transversely across the vein 
and separated from one another by the naked, scaleless parts of the vein. 
On these dilatations stand densely packed scent-scales, whose shape 
reminds one rather of those of many Satyridae than of the other Maracuja 
butterflies. 
However much one may be accustomed to find so-called “secondary 
sexual characters ” taking very different forms in closely allied species, 
I was surprised to find such a radical difference within such an exclusive 
circle as that of the Maracuja butterflies. The surprise vanished when I 
became convinced that the arrangement of the scent-scales in Dione 
vanillae is connected with that of the other Maracuja butterflies, by 
intermediate forms. 
In Heliconius, where the scent-scales are confined to that part of the 
hind-wing covered by the fore-wing, they are always most numerous along 
the veins. In Golaenis dido male, as I believe I mentioned in my first 
communication, the scales are not confined to that one spot, but scattered 
over the whole wing, and, as a more accurate investigation has now shown, 
they occur exclusively on the veins. They are found on veins 2-8 of the 
hind-wings, also on 1-7 of the fore-wings, being most numerous on those 
veins of the hind-wings which are covered by the fore-wings. All the 
1 Kosmos, II. (1877-78), pp. 38-41. 
