VII. COSTAL FOLD OF HESPERIDAE 
643 
The marginal nervure (Fig. 13 M) is furnished with more or less 
curved scales of oval or orbicular shape (Fig. 14). The whole internal 
surface of the costal fold, from the costal to the marginal nervure, is 
clothed with scales or thick hairs of various forms. 
Along the curved margin there are pale scales (Fig. 15), oval in shape, 
about 0*01-0*03 mm. in breadth, and with rounded apex. At the base of 
the angle formed by this margin and the rest of the wing, the scales are 
less pale, opaque, very narrow, tapering to a fine point (Fig. 18), and about 
0*08 mm. long by 0*005 mm. broad. Finally, on that part of the wing which 
is covered by the folded margin there are scales of two very different shapes : 
the first (Fig. 17) are lanceolate, about 0*14-0*17 mm. long by 0*03-0*04 mm. 
broad ; the second (Fig. 16) are far more slender, transparent, tubular, 
varying from 0*2 to 0’27 mm. in length, and from 0*002 to 0*006 mm. in 
breadth. Gradually diminishing in size, these latter scales are terminated 
by an extremely fine thread, bearing at its apex a very small lamina, shaped 
like an obtuse-angled isosceles triangle. The sides of this triangle are 
marked with very fine, almost imperceptible lines, which, at first sight, are 
only seen at the base as straight lines perpendicular to the extremity of the 
sustaining thread. 1 These singular scales of Hesperia syrichthus (Fig. 16), 
although apparently so different from those of Telegonus mercatus , may, 
nevertheless, be easily derived from the same form (Fig. 11 i). 
Leucochitonea arsalte, Linn. (PI. G, Figs. 19-22). The costal fold of 
the males is much smaller than in the last species, occupying scarcely one- 
third of the costal margin of the wing, and less than half the breadth of 
the space between the margin and the costal nervure. 
The down enclosed in the fold arises only from the surface of the 
folded margin, and is protected by two lines or fringes of scales, one of 
which is inserted along the marginal nervure (Fig. 20 M), the other along 
the straight line which separates the folded portion from the rest of the 
wing : the latter scales are about as long as they are broad, but much shorter 
than those on the marginal nervure. The down is composed of scales of 
two different forms, similar to those in Hesperia syrichthus. 
Those of the first form (Fig. 21) are like a spear head ; the length is 
about 0*15 mm.; the breadth varies from one-ninth to one-fourth of the 
length, and is greatest at, or close to, the point of insertion, from whence 
a line runs almost straight to the sharp apex of the scale. These scales, 
which evidently correspond to those of Hesperia syrichthus in PI. F, Fig. 17, 
are pale, transparent, the apex more or less opaque, the base having almost 
always a longitudinal stripe, composed of opaque granules. The scales of 
the second form (Fig. 22) corresponding with those in PI. F, Fig. 16, are 
about the same length, 0*15 mm., but so slender as almost to deserve the 
name of hairs, being rarely as much as 0*002 mm. broad, and usually 
1 It is probable that the meaning of this difficult passage would be more clearly 
conveyed by substituting the words “ radiating from ” for “ perpendicular to.”— 
E.A.E., E.B.P. 
