favourites with collectors, that the student of distribution and
variation will find his materials the most satisfactory, from their
comparative completeness.

Pre-eminent among such groups are the diurnal Lepidoptera or
Butterflies, whose extreme beauty and endless diversity have led to
their having been assiduously collected in all parts of the world, and
to the numerous species and varieties having been figured in a series of
magnificent works, from those of Cramer, the contemporary of Linnaeus,
down to the inimitable productions of our own Hewitson.[G] But, besides
their abundance, their universal distribution, and the great attention
that has been paid to them, these insects have other qualities that
especially adapt them to elucidate the branches of inquiry already
alluded to. These are, the immense development and peculiar structure of
the wings, which not only vary in form more than those of any other
insects, but offer on both surfaces an endless variety of pattern,
colouring, and texture. The scales, with which they are more or less
completely covered, imitate the rich hues and delicate surfaces of satin
or of velvet, glitter with metallic lustre, or glow with the changeable
tints of the opal. This delicately painted surface acts as a register of
the minutest differences of organization--a shade of colour, an
additional streak or spot, a slight modification of outline continually
recurring with the greatest regularity and fixity, while the body and
all its other members exhibit no appreciable change. The wings of
Butterflies, as Mr. Bates has well put it, "serve as a tablet on which
Nature writes the story of the modifications of species;" they enable us
to perceive changes that would otherwise be uncertain and difficult of
observation, and exhibit to us on an enlarged scale the effects of the
climatal and other physical conditions which influence more or less
profoundly the organization of every living thing.

+--------------------------------------------------------------+
| [G] W. C. Hewitson, Esq., of Oatlands, Walton-on-Thames, |
| author of "Exotic Butterflies" and several other works, |
| illustrated by exquisite coloured figures drawn by himself; |
| and owner of the finest collection of Butterflies in the |
| world. |
+--------------------------------------------------------------+

A proof that this greater sensibili