VII. COSTAL FOLD OF HESPERIDAE 
645 
gradually into an extremely fine thread, at whose extremity a very small 
punctiform button may sometimes be found (Fig. 27 e). There are also 
usually other scales, shorter, broader, and opaque, resembling those of the 
first type (Fig. 27 /; Fig. 28 c). The costal fold occupies about the 
middle of the anterior margin of the wing, and is rather narrow. 
If in all the districts inhabited by Thymele simplicius the males with¬ 
out the costal fold are chiefly distinguished, as they are here, by the 
prolongation of the transparent band beyond the second nervure, I 
consider that they should be ranked as a distinct species, and not as a 
mere variety. However this may be, it is worthy of notice that of two 
similar forms, included by Herrich-Schaeffer and others under a single 
variety, one has the costal fold well developed, while the other is entirely 
destitute of it. 
It appears that this absence of the costal fold in some males of Thymele 
simplicius has not been previously noticed. Such males have probably 
been mistaken for females, just because of the want of these folds, a 
mistake pardonable in any one unable to examine the living insects, in 
which case the sexes are easily distinguished by the genitalia. 
Thymele protillus , Herr.-Sch. (PL G-, Fig. 30). The costal fold covers 
about half the anterior margin of the wing, and extends a little beyond 
the transparent spot in cell 12. There are in the interior of the fold :— 
1. Scales of about 0*3 mm. long, with lanceolate base, terminated by a 
lamina which is either rounded, oval, triangular, or cordiform, and of 
variable breadth (Fig. 30 a ); 2. Very fine hairs of the same length 
(Fig. 30 b) ; 3. Narrow scales (Fig. 30 c) almost parallel sided, about 
0T2 mm. long and scarcely 0*004 mm. wide, terminating abruptly in a 
very fine, almost imperceptible thread ; 4. Not very abundant fragments 
of the articulated hairs (Fig. 30 d). 
Thijmele proteus, Linn. (PI. G-, Fig. 29). In this species, which is very 
similar to the last, the costal fold does not extend beyond the transparent 
spot in cell 12, and is even narrower than in Th. protillus . In the fold, 
jointed transparent hairs predominate (Fig. 29 c): the joints are 0*016 mm. 
to over 0*03 mm. long, and rarely more than 0*004 mm. wide. There are 
usually 7 to 12 of these joints united together. Besides these there are 
other scales of which the majority are about 0*2 mm. long by 0*02 mm. broad: 
they are pale, and traversed by a longitudinal, granular, opaque stria. In 
form they are slightly attenuate towards the base, and terminate in a 
small elliptical lamina, the width of which does not exceed, or even equal 
that of the base (Fig. 29 a). There are some smaller scales of a similar 
shape with a much narrower terminal lamina, and without the opaque 
longitudinal streak (Fig. 29 b). 
Entheus vitreus , Cram. The costal fold of this elegant species is very 
narrow, and encloses jointed, transparent hairs. The joints, of which 
about ten or more are connected, are usually 0*015 mm. long by 0*004 mm. 
wide, but they are very variable in both these dimensions. 
