316 Plumules or Battledore Scales 
it is necessary to brush off the dirt which may he on the wing with 
a camel-hair pencil ; but then care must be taken that the pencil 
does not convey scales to slides of other species ; and, in fact, 
suspicious care must be used when mounting a number of slides, as 
the light scales will often be floating in the air and alighting unex- 
pectedly on the slide which is under operation. Then cover with a 
thin glass, and fix with paper. In some small insects it is more 
convenient to take off the scales in the first instance on the thin 
cover, and then to affix it to the slide. The plumules are mostly 
of so delicate a membranous structure, and so deficient in pigment, 
as to become too transparent (and sometimes almost invisible) in 
Canada balsam ; but it may be used with good effect where they 
carry some amount of pigment ; and the structure of those of the 
Lycmnidse is thereby beautifully shown, although these are among 
the most hyaline. In some genera and species they are so small 
and so finely striated as to make a ^-inch object-glass desirable to 
resolve them satisfactorily, or at least a J, with a B or C eye-piece ; 
while a J-inch is sufficient for others. 
The striae particularly should be observed with high powers. 
Occasionally scales of different species appear under a low power 
identical, but a higher one reveals a complete difference of structure. 
Taking for our text-book the ' Genera of Diurnal Lepidoptera ' 
of Doubleday, Westwood, and Hewitson, we proceed to state the 
additional families and genera where the plumules have been found. 
Throughout this work there is evidenced an inkling of the writer's 
appreciation of the value of the scales, or of some of them, for aid in 
classification, but more in the direction of genera than of species ; 
and the distinct character of the plumules is not recognized, nor the 
probability remarked that the insects are furnished with two classes 
of scales, as was suggested in a former article. In the consolidated 
treatise we are undertaking, w^e shall notice, seriatim, aU the 
families and genera, with remarks on peculiarities of some scales, 
even when they do not assume the form of plumules. 
In the work above named, the Diurnal Lepidoptera are divided 
into fifteen families. 
Family I. Papilionid^. — No plumules found. 
Family II. Pierid^.— Found on many species already men- 
tioned. 
Family III. Ageronid^. — None. 
Family lY. Danaid^. — It is in the genus Euplcea only of this 
family that plumules have been found ; and they bear a very different 
form from that of those of other genera, with the exception of an ap- 
proach in Pieris Lyeimnia, Plate XXXIV, Fig. 7.* The typical 
form of Euj)loea is shown in Plate XXXIV, Figs. 1 and 2 ; and I have 
found them on thirteen species, whether or not all distinct may be 
' * The plates have been drawn by Mr. Sidebotham, specially for the illustra- 
tion of this paper. 
