622 
APPENDIX 
discoidal [radial or second discoidal] (5) nervures, and [within the cell] by 
a line from the point of separation of the costal and subcostal to the 
point at which the lower discocellular leaves the discoidal; it runs along 
the costal nervure for about two-fifths of its length, and along the dis¬ 
coidal to a point midway between the margin of the wing and the point 
of separation of the costal and subcostal. This spot occupies about one- 
eighth of the surface of the wing, being nearly a semicircle of 12 mm. 
diameter, while the whole wing is about equal to a circle of 24 mm. 
diameter. 
This patch is usually covered by the fore-wing, the lower surface of 
which is provided (PI. B, Fig. 11, w!) with a patch, opposite to that on the 
hind-wing, and almost identical in its felted appearance, colour, form, and 
size. It is, however, less conspicuous, not only from contrasting less with 
the colour of its surroundings, but also from being entirely covered with 
a mane of black hair, inserted along the internal [submedian] nervure (1). 
This felted patch on the fore-wings extends from the internal [sub¬ 
median] nervure (1) to the angle formed by the second and third branches 
(nervures 3 and 4) of the median, and, as in the hind-wings, an insignifi¬ 
cant part of the patch enters the cell. 
The mane, which has been just mentioned, starts from the posterior 
margin of the patch, or, what comes to the same thing, from the anterior 
margin of the internal [submedian] nervure. If this nervure be considered 
as divided into five equal parts, the second and third of these parts, 
counting from the base of the wing, are occupied by a mane composed of fine 
[in the sense of “ beautiful ”] black hairs of about 7 mm. in length. This 
mane covers exactly and entirely the felted patch of the fore-wings, and at 
the same times separates it from that on the hind. 
The scales of the felted, or odoriferous patch (PI. B, Fig. 13) are 
distinguished from ordinary scales (Fig. 12). 
First, by their shape, which chiefly differs in the non-dentate ends. 
Second, by their size. Of the ordinary scales on the upper surface of 
the wings, the overlying (PI. B, Fig. 12 s) run about 0T4 mm. in length 
by 0*06 mm. in breadth ; the underlying (Fig. 12 i) about 0T long by 0*08 
broad. The overlying scent-scales (Fig. 13 s) measure from 0*33 mm. long 
by 0*1 broad ; the underlying (Fig. 13, i) about 0*24 long by 0*11 broad. 1 
Third, in being much more opaque and apparently without the 
longitudinal lines found on ordinary scales. 
Fourth, in being more firmly fixed to the membrane of the wing, so 
that by passing a brush over the surface of the wing, one can remove the 
ordinary scales and leave those of the felted patch. 
All these differences between the ordinary and the scent-scales exist in 
nearly every species which bears scent-patches upon its wings. The 
1 The reference letters s and i are accidentally transposed in Fig. 13 of the original 
plate.—E.B.P. 
