262 MR. J. WATSON ON THE PLUMULES OR 



tion. 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 afiix it to the slide. The plumules are mostly of so 

 delicate a membranous structure, and so deficient in pig- 

 ment, 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 Lyccenidce 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 -f-inch object-glass desirable to re- 

 solve them satisfactorily, or at least a 5, with a B or C eye- 

 piece ; while a f -inch is sufficient for others. 



The strise 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 Le- 

 pidoptera^ 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, we shall notice, seriatim, all 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 15 families. 



